Question: Three Stage Vs Modulating

[cpetku]

So with similar sized systems and pricing for a 2500 Sq Ft house in Michigan I have to which contractor to go with based upon my gut feeling aftger interviewing the salemen regarding their company and feedback from this forum.

1) Is there a significant comfort advantage between a 3 Stage Bryant/Carrier Infinity (355CAV... and a Modulating York furnace (PC9-UP...) Both 4 ton AH and 100K input.

2) Bryant offers a 20 Year parts and Labor warranty on the HX whereas York offers lifetime parts (no labor). Are either of these warranties significant (failure rates of current equipment) and would most contractors servicing a Bryant with a failed HX fix it or try selling a new unit with a 30% (or so) credit which is probably the actual York strategy...

3) By buddy's 10 year old Bryant recently had the secondary HX fall apart. Have the new units changed the secondary HX design or materials? Does York have any real HX issues in their 90%+ line (I don't see class actions on York, but I do for Bryant)?

4) Any feedback on the reputation of Andy's Statewide (Orion) Vs Top Notch Mechanical (Waterford) regarding solving post installation problems (if this is against the rules, then please disregard). The BBB only lists Andy's with 2 resoloved issues.

[Jim Davis]

If you are comfortable having cold air blowing out of your registers and the highest gas bill on the block either one will work.

[cpetku]

So what you're saying is that both of these systems which claim to be high-comfort solutions are really mis-leading the consumer. Thus based upon the brevity of your statement I guess from a comfort viewpoint I'm better off keeping my 20 year old single stage single speed Goodman 70% and investing in T-notes to compensate for the difference in fuel costs...

[BaldLoonie]

If you go the Carrier be sure to get the Infinity control for best operation of the 3 stages. York's furnace does it all off of a single stage stat, not my favorite idea but with logic and temp sensors it works. Personally either would do the job. The Infinity control can do more with airflow and dehumidifcation if that's of any interest.

The issues with the Bryant/Carrier heat exchangers have been minor and are under warranty. Those furnaces are ALL OVER the place around here. We sure go through a lot of control boards but very rare to have a secondary heat exchanger problem on the 40" models, the ones sold today. The first generation 90s did have some issues with their secondary plugging up with junk & caulk.

We never hear complaints of cold air from our 2 stage furnace sales and nobody has ever complained about gas bills going UP on multistage furnaces. Our former Rheem supplier said his gas bill went down going from a single stage 90 to Rheem's Modulator.

[RoBoTeq]

Modulating vs three stage is getting pretty sensitive. In theory, the modulating furnaces are going to be more comfortable. I also have not heard of cold air from the registers being an issue unless there is a problem with the way the systems have been set up.

As far as the cost factor, staged furnaces can be more costly to operate if they are oversized. A properly sized staged furnace will provide both comfort and efficiency.

[airdata870]

If you are comfortable having cold air blowing out of your registers and the highest gas bill on the block either one will work.Would you care to speak more about this? i have not heard of this being a issue. thanks.

[RoBoTeq]

Would you care to speak more about this? i have not heard of this being a issue. thanks.
Ho boy, are you asking for it. Then again, I'm not sure if Captain CO is really much on discussing his views:rolleyes:

[mayguy]

If you are comfortable having cold air blowing out of your registers and the highest gas bill on the block either one will work.

I too question about this too???

Went from old single stage gas on a gas budget pay of $180 a month down to $88 a month on a two stage, and have nice warm air out of the vents, house is more comfortable now than it was with the single stage...

[RoBoTeq]

I too question about this too???

Went from old single stage gas on a gas budget pay of $180 a month down to $88 a month on a two stage, and have nice warm air out of the vents, house is more comfortable now than it was with the single stage...
The staging has nothing to do with your gas usage drop. That is strictly a factor of proper sizing and a more efficient furnace. Your comfort level increase is a direct result of the two stage feature, again along with the fact that your furnace has been properly sized.

[tinknocker service tech]

i may be wrong but i believe they are both stageing furnaces. York just has more stages then the others.

I believe lennox is the only one that has a true modulating gas valve and the rest are staging.

like i said i could be wrong

[RoBoTeq]

i may be wrong but i believe they are both stageing furnaces. York just has more stages then the others.

I believe lennox is the only one that has a true modulating gas valve and the rest are staging.

like i said i could be wrong
As far as I know it is Rheem/Ruud that has the only truly modulating system that they have had out since the 1990's.

[jrbenny]

As far as I know it is Rheem/Ruud that has the only truly modulating system that they have had out since the 1990's.
Might want to read a bit about your new product line. :rolleyes:

:D

[tinknocker service tech]

As far as I know it is Rheem/Ruud that has the only truly modulating system that they have had out since the 1990's.


the G-71 has a valve that will modulate up and down by the presure differantial accross the heatexchanger cause by the drat induce ramping up
this is determined by the board

it is also set to give the btu you need to heat your house and not run all the time.

it ramps up and then off. And is controled by stat and time and the board determines what btu it starts at each time it starts and will modilate up from there at certain percentages

i i remember right the rheem stages up and down determined by the stat. I am not sure it works off time also but it doent modulate from my understanding only stages

[Jim Davis]

Both the low 3rd stage and the low fire on modulating furnaces have been tested in the field to deliver only 38% efficiency. Familiar with a consumer that had 40% higher gas bills with his 90% modulating furnace than his neighbor with a single stage 90%. In fact after 2 years he has just had it removed. Some of the new modulating and staging furnaces have slowed their blowers down to keep the air warmer which is at least an improvement.

Some new two stage furnaces are now bringing on high-fire first (wow lets produce the most heat when the house is the coldest) which is saving quite a bit more money because these furnaces don't spend anytime in low-fire.

When someone states they saved after switching from a single stage to a two stage it usually means the single stage was really screwed up by whoever installed it or your new two-stage is running most of the time in high fire and that would be good.

Sizing affects comfort more than efficiency. A furnace that is 100,000 btus versus one that is 50,000 btus use exactly the same amount of energy to heat if they are both operating at the same efficiciency. The 100,000 btu runs 50% less to heat the house.

Only those contractors that do performance testing and use combustion analyzers on all jobs would know the truth. None of them have posted here yet but they will.

Carrier Infinity is one with a new stat that does bring on high-fire first. Others have switches to jump out the staging(too many complaints).

Variable speed blowers save lots of money and are only available on staging equipment. Therefore multi-stage equipment (90% only) needs to purchased and then set up properly in the field.

Efficiency of furnaces is based more on a points system than actual testing. No furnace has ever been tested or rated in any firing rate other than high fire.

[RoBoTeq]

Might want to read a bit about your new product line. :rolleyes:

:D
Like I've mentioned, I really do not know the Luxaire line very well at all. I've been busy learning as much as I can about the ClimateMaster line and hydronics in general since these are better selling products for me at the moment. By the end of next week, I will be an expert on Luxaire. Better not be anyone dissing Luxaire after next week;).

[RoBoTeq]

Both the low 3rd stage and the low fire on modulating furnaces have been tested in the field to deliver only 38% efficiency. Familiar with a consumer that had 40% higher gas bills with his 90% modulating furnace than his neighbor with a single stage 90%. In fact after 2 years he has just had it removed. Some of the new modulating and staging furnaces have slowed their blowers down to keep the air warmer which is at least an improvement.

Some new two stage furnaces are now bringing on high-fire first (wow lets produce the most heat when the house is the coldest) which is saving quite a bit more money because these furnaces don't spend anytime in low-fire.

When someone states they saved after switching from a single stage to a two stage it usually means the single stage was really screwed up by whoever installed it or your new two-stage is running most of the time in high fire and that would be good.

Sizing affects comfort more than efficiency. A furnace that is 100,000 btus versus one that is 50,000 btus use exactly the same amount of energy to heat if they are both operating at the same efficiciency. The 100,000 btu runs 50% less to heat the house.

Only those contractors that do performance testing and use combustion analyzers on all jobs would know the truth. None of them have posted here yet but they will.

Carrier Infinity is one with a new stat that does bring on high-fire first. Others have switches to jump out the staging(too many complaints).

Variable speed blowers save lots of money and are only available on staging equipment. Therefore multi-stage equipment (90% only) needs to purchased and then set up properly in the field.

Efficiency of furnaces is based more on a points system than actual testing. No furnace has ever been tested or rated in any firing rate other than high fire.
Give us a break here Jim. For crying out loud, some of us have reports from hundreds of contractors stating that new 2 stage and modulating furnaces have been reported by their customers to have saved them money.

When a new high efficiency furnace does not reduce gas bills, people like me hear about it pronto.

Not every furnace has to have someone who has taken your course in order to function properly and to be efficient. Jeez Jim, give the rest of the world at least a little bit of credit for being able to function without you:rolleyes:.

[Jim Davis]

What are you doing up so late?

You know I am not making this up!! Just in the last two weeks I have been out in the field testing brand new two stage and three stage equipment. If people are saving money with new furnaces operating at less than 50% efficiency in low fire, the old furnace had to be pretty screwed up. Bring on high-fire first and thats is another story.

Did I mentioned most of the furnaces that are really bad aren't the ones you are familiar with??

Old people have been complaining about new two-stage furnaces since the day they came out. Saving people 5% or 10% instead of 30%-40% makes it okay?? Like I said the old equipment had to be really messed up.

I got a feeling that there are going to be alot more complaints this winter than in the past. The standard excuse will be it is colder and fuel costs more
and that good enough.

NO everyone doesn't have to take my course, because even a blind squirrel finds a nut now and then.

I have not found one person in the country that knows how to set the blower speed on the furnace for heating until they attended my class or spoke to someone that did. I would think that would be important seeing how bad airflow causes many cracked heat exchangers.

Combustion analyzers don't make equipment efficient, the person using it does. Not one manufacturer of analyzers teach how to maximize efficiency of equipment, so where would one learn??

[Jim Davis]

Many blind squirrels have found this nut. But when I told them to move their tales out of their eyes they realized they weren't blind.:D

[RoBoTeq]

If I were a blind squirrel I would be able to find at least two nuts:D.

I have been finding more and more contractors who are always concerned with the proper airflow of furnaces and always adjust airflow to a central point between the temperature rise extremes. Jim, I think you have become jaded because you only see the bad;).

I also am finding more and more contractors are actually setting gas pressures along with temperature rise on installation of furnaces. I cannot vouch for all manufacturer's reps, but everyone I have worked for since 1998 has been very diligent in teaching that furnaces are not plug and play appliances and that they need to be properly set up. Of course, some of us also disagree on what is proper set up.

[Jim Davis]

See, like I said no one knows how to set up airflow correct on heating until they are taught. The only gas pressure that most contractors set is 3-1/2" which is hardly ever correct. If burner orifices were drilled accurately(not possible) and we could get 1050 btu out of every cubic foot of gas(never can happen) this would be correct. But they do wear pretty blue booties.

[RoBoTeq]

See, like I said no one knows how to set up airflow correct on heating until they are taught. The only gas pressure that most contractors set is 3-1/2" which is hardly ever correct. If burner orifices were drilled accurately(not possible) and we could get 1050 btu out of every cubic foot of gas(never can happen) this would be correct. But they do wear pretty blue booties.
Draft is also never consistant as well as gas btu values are not consistant. Manufacturer's specifications allow a buffer for variances. Then again, this is old stuff between you and I.

As for the blue booties, some are also red, let's not get political here;). The booties offer the perception that the technician is professional and perception is reality in the mind of the consumer:p.

[I_bend_metal]

Hmmmm....and to think I was under the impression that a BTU was a BTU....doesn't matter how many of them are flowing, it still takes the same amount of them to raise the temperature in a home. So in low fire, it runs longer....still uses just as much gas to get to 72 degrees.....In high fire, it doesn't run as long....still uses just as much gas to get to 72 degrees. I thought this was one of the first things they taught us about 2 stage furnaces....they don't save gas....they provide better comfort.



I'm sure someone will be along soon to correct me......;)

[JBM1000]

Seems odd that the Factory class I went to kept pushing "comfort" verses actual efficiencies!!

[Jim Davis]

Hmmmm....and to think I was under the impression that a BTU was a BTU....doesn't matter how many of them are flowing, it still takes the same amount of them to raise the temperature in a home. So in low fire, it runs longer....still uses just as much gas to get to 72 degrees.....In high fire, it doesn't run as long....still uses just as much gas to get to 72 degrees. I thought this was one of the first things they taught us about 2 stage furnaces....they don't save gas....they provide better comfort.



I'm sure someone will be along soon to correct me......;)

Correct, a btu is a btu, but the actual operating efficiency determines how many btus are needed to heat a house. A furnace running at 50% efficiciency needs 100,000 btus input to accomplish this. A furnace running at 75% efficiency only need 75,000 btus input to accomplish the same thing.

Low fire operates below 50% efficiency on all equipment tested in the field to date regardless of its rating.

[Jim Davis]

Draft is also never consistant as well as gas btu values are not consistant. Manufacturer's specifications allow a buffer for variances. Then again, this is old stuff between you and I.

As for the blue booties, some are also red, let's not get political here;). The booties offer the perception that the technician is professional and perception is reality in the mind of the consumer:p.

Do independents wear purple booties?:(

Manufacturers allow buffers for more than variances. They know that 98% of contractors never perform actual testing in the field other than an occasional gas pressure test and take no chances and intentional over underfire, well, with a few exceptions.

[mark beiser]

http://www.clipartof.com/images/emoticons/xsmall2/1974_eating_popcorn.gif

[Freezeking2000]

I am going to stay away from this. I do not believe for a minute that a 97.5 furnace will run at 50%. I do not believe a combustion test can show proper readings on modulating furnaces if thats the case.

The new York. Luxaire vary the blower motor on all models, not just using 2 or 3 speeds either. Also the induced draft motor varies as well.

Do not believe this thread.................!

[davidr]

I am going to stay away from this. I do not believe for a minute that a 97.5 furnace will run at 50%. I do not believe a combustion test can show proper readings on modulating furnaces if thats the case.

The new York. Luxaire vary the blower motor on all models, not just using 2 or 3 speeds either. Also the induced draft motor varies as well.

Do not believe this thread.................!

Well if I had not seen this very thing occurring in the field I would agree with you 100% freezeking.

Problem with that is I have seen it.

A lot of the issue boils down to how those efficiencies are actually derived in laboratory conditions.

If we sell a customer a furnace that is rated at 90,000 BTUs output and this same piece of equipment combined with the duct system it's attached to only delivers 45,000 BTUs output into the building envelope; have we done our job?

Looks to me like they are only getting 50% of what they paid for.

[cpetku]

Looks like I stumbled onto a highly debated subject in asking what I thought would be a simple question with an answer like they both work about the same and you'll be happy with either...

Since I have not signed with any contractor or decided on a brand but merely know that I want a high efficiency 95+ Variable speed unit to go with an Air Sorce Heat pump. I assume that the furnace won't be used except when the HP can't keep up.

Would a typical installer setup the system, for GAS heat only in the high stage assuming the outside temp has already passed the need for 30KBTUh?

One of the concerns I had was when the system changes over to Gas, will the furnace start at low fire and take awhile to figure out it really needs to be medium or high....

Also, since the Sales people who have sent quotes don't really beleive in Manual J I did my own 36K gain / 88K loss Should I expect the HP to be sized higher than 3 Ton?

[House]

Well if I had not seen this very thing occurring in the field I would agree with you 100% freezeking.

Problem with that is I have seen it.

A lot of the issue boils down to how those efficiencies are actually derived in laboratory conditions.

If we sell a customer a furnace that is rated at 90,000 BTUs output and this same piece of equipment combined with the duct system it's attached to only delivers 45,000 BTUs output into the building envelope; have we done our job?

Looks to me like they are only getting 50% of what they paid for.

I had an 80% efficient Armstrong builder's special replaced with a 92.8 efficient Rheem mod last December. My seasonal savings based on heating-degree days was ZERO. My house consistently uses 0.083 (+- 0.02) Therms/HDD over the past four years.

As far as I'm concerned, the 13% savings I was supposed to get was lost in the ductwork due to the lower average airflow.

[cpetku]

Since I caused the bickering, here's a link to a document I found on a government website on the subject. Looks like Captian CO has a basis for his statements. Now if only I could figure out the best way to buy a new system to keep on of you local guys employed...

http://www.osti.gov/bridge/product.biblio.jsp?osti_id=804678

[Jim Davis]

You are a consumer that asked a simple question and I answered with the truth based on real field testing and experience. A two stage variable speed 90% is the best selection but then the furnace needs to be tuned or adjusted for high fire only. Manufacturers have already started adding bypass switches or making thermostate bring on high fire first for some reason. Find a contractor that know the difference and actually measures system performance after he installs it.

[hvaclover]

Man, this is turning into BS. i am not as versed as Robin or Davis, but when I set a furnace up to a temp rise in the middle of btw 45 and 75* and try to get as close to a 120* supply as I can, and clocking the meter tells me my furnace is putting out at the GAMA rating I know I have done my job.

And five years worth of crunching customer gas bills against how many degree days over the period, I know my customers have saved money on their gas bills from the 90%ers I have installed.

There is some dgree of self promotion here but I have never known Robin to a uninformed person.

Hey Jim Davis are you ever going to answer that PM I sent you?

[RoBoTeq]

Correct, a btu is a btu, but the actual operating efficiency determines how many btus are needed to heat a house. A furnace running at 50% efficiciency needs 100,000 btus input to accomplish this. A furnace running at 75% efficiency only need 75,000 btus input to accomplish the same thing.

Low fire operates below 50% efficiency on all equipment tested in the field to date regardless of its rating.
Agreed. Also, the heat transfer rate is slower and less in low fire. I have abolutely had complaints that a new two stage furnace cost more to operate then the old furnace did. Every one of these furnaces were oversized.

[RoBoTeq]

Since I caused the bickering, here's a link to a document I found on a government website on the subject. Looks like Captian CO has a basis for his statements. Now if only I could figure out the best way to buy a new system to keep on of you local guys employed...

http://www.osti.gov/bridge/product.biblio.jsp?osti_id=804678
Captain CO is correct in the things he states. Unfortunately Capt. CO's technically accurate scary stories do not answer your question. Either of those furnaces, properly sized and properly installed will do you well. The modulating furnace has the capability of providing more comfort, but may not be able to be noticeable to the average person.

The most important factor is that the furnace not be oversized. If the furnace is oversized, it will operate too often only in low fire and will be inneficient overall.

Don't let the scary Captain upset you. His expertise is best put to use after the install if there is a problem that standard set up parameters won't address.

I will say that if the Captains companies training were employed by every contractor, the world would be a better place:cool:. That does not mean that companies not employing the Captains training methods are doing anything wrong and that proper manufacturer set up will not provide comfort and efficiency.

[RoBoTeq]

You are a consumer that asked a simple question and I answered with the truth based on real field testing and experience. A two stage variable speed 90% is the best selection but then the furnace needs to be tuned or adjusted for high fire only. Manufacturers have already started adding bypass switches or making thermostate bring on high fire first for some reason. Find a contractor that know the difference and actually measures system performance after he installs it.
The new algorythmic control boards that control the staging by furnace run time are set up to bring on the high fire more often, I believe for this very purpose along with burning off possible condensate in the primary heat exchangers. We are learning how to build better mousetraps.

[RoBoTeq]

Man, this is turning into BS. i am not as versed as Robin or Davis, but when I set a furnace up to a temp rise in the middle of btw 45 and 75* and try to get as close to a 120* supply as I can, and clocking the meter tells me my furnace is putting out at the GAMA rating I know I have done my job.

And five years worth of crunching customer gas bills against how many degree days over the period, I know my customers have saved money on their gas bills from the 90%ers I have installed.

There is some dgree of self promotion here but I have never known Robin to a uninformed person.

Hey Jim Davis are you ever going to answer that PM I sent you?
Jim's specific technical knowledge could make me seem like a first grader on the subject of furnace combustion and I respect his teachings very much. Where Jim and I split is on how much of a buffer needs to be considered with furnace combustion set up and how much tweeking is actually worth the cost on all but special issue systems.

Jim's intent is to have every technician be perfect on every job in the assumption that the HO will provide proper maintenance and that no oddities that occur often will occur with furnaces set up to his teachings standards.

My intent is more practical in that I want technicians to leave a furnace in a manufacturer's specified condition to provide comfortable, efficient heat for the HO with enough leeway to account for problems caused by closing of vents, not changing the filters properly, installing too restrictive of filters, gas Btu values changing etc.

What your parameters are for leaving a furnace are what I prefer technicians to do. Just don't put too much credence on that leaving air temperature. With a 60 degree temperature rise and 60 degree return air temperature, you will still have 120 degrees leaving air temperature. Raise that return air to 72 degrees and your leaving air will be 132 degrees.

[hvaclover]

Jim's specific technical knowledge could make me seem like a first grader on the subject of furnace combustion and I respect his teachings very much. Where Jim and I split is on how much of a buffer needs to be considered with furnace combustion set up and how much tweeking is actually worth the cost on all but special issue systems.

Jim's intent is to have every technician be perfect on every job in the assumption that the HO will provide proper maintenance and that no oddities that occur often will occur with furnaces set up to his teachings standards.

My intent is more practical in that I want technicians to leave a furnace in a manufacturer's specified condition to provide comfortable, efficient heat for the HO with enough leeway to account for problems caused by closing of vents, not changing the filters properly, installing too restrictive of filters, gas Btu values changing etc.

What your parameters are for leaving a furnace are what I prefer technicians to do. Just don't put too much credence on that leaving air temperature. With a 60 degree temperature rise and 60 degree return air temperature, you will still have 120 degrees leaving air temperature. Raise that return air to 72 degrees and your leaving air will be 132 degrees.

Thanks Robin. 120* is an ideal I shoot for with a right sized 90% but it is not always atainable because of under size ducts. But I am trying to get a 45* rise which at 120 supply gives me 75* return. Gotta good ductsizing for that.

Just want the ht ex to last longer than the warrany.

[hvaclover]

Jim's specific technical knowledge could make me seem like a first grader on the subject of furnace combustion and I respect his teachings very much. Where Jim and I split is on how much of a buffer needs to be considered with furnace combustion set up and how much tweeking is actually worth the cost on all but special issue systems.

Jim's intent is to have every technician be perfect on every job in the assumption that the HO will provide proper maintenance and that no oddities that occur often will occur with furnaces set up to his teachings standards.

My intent is more practical in that I want technicians to leave a furnace in a manufacturer's specified condition to provide comfortable, efficient heat for the HO with enough leeway to account for problems caused by closing of vents, not changing the filters properly, installing too restrictive of filters, gas Btu values changing etc.

What your parameters are for leaving a furnace are what I prefer technicians to do. Just don't put too much credence on that leaving air temperature. With a 60 degree temperature rise and 60 degree return air temperature, you will still have 120 degrees leaving air temperature. Raise that return air to 72 degrees and your leaving air will be 132 degrees.

Thanks Robin. 120* is an ideal I shoot for with a right sized 90% but it is not always atainable because of under size ducts. But I am trying to get a 45* rise which at 120 supply gives me 75* return. Gotta have good ductsizing for that.

Just want the ht ex to last longer than the warranty.

[cpetku]

Based upon my final loss (80K) and load (34K Sensible) numbers and the feedback in this thread I believe the following systems will meet my needs better than the original proposals

Sys #1 Bryant 355BAV 100K in (not CAV) and 286 4 Ton 16 Seer HP
Sys #2 York 2 Stage Affinity 100K in and 18 Seer HP (9.8 HSPF is the deciding factor)

My thanks to all who participated in this thread as it has given me insight into the complexity of selecting the appropriate equipment and ensuring that the contractor I select knows why he is matching a certain furnace with a specific heat pump. It also gave me cause to run my own manual-J (something 3 out of 4 contractors refused to do). I'ts now obvious why pro's should do these calcs before recomending equipment and the need to actually measure the insulation thickness in the walls.

[larryb]

Hi:

Just this month I had a 100Kbtu 80% replaced with a 75Kbtu Rheem mod, model RGJD. What I am reading here is somewhat of a concern. I picked the unit for both efficiency and comfort. Here is what I've observed so far:

The unit is very comfortable, and most of the time you can hardly hear it. I haven't had it long enough, and the temp is mild enough so far, that I don't have a handle on gas usage.

I programmed my home automation controller to read the thermostat PWM signal. When bringing up the house in the morning, the T-stat starts at 100% and ramps down to 40% before shutoff. When cycling to maintain temp, it starts at 60% and ramps down to 40% before shutoff.

Now, my question for Captain CO and RoBoTeq: Do you believe the mod or staged furnaces are less efficient on low-fire due to the furnace itself, or conduction loss in the ductwork because the furnace spends more time on? As an engineer, I'm interested in as much detail as you are comfortable providing.

Thanks, Larry

[cvcman]

if these companys selling these units do not tell their customers that these are 50% efficient running at low stage I would think they can be held liable.

Mine always fires and runs at low UNLESS it has to raise the temp more han 2 degs which the only time it does this is after a setback of 5 degs at night. Then it goes to high.

I have only had it 3 months so not an real cold weather yet but im thinking of calling the company Monday now that I hear this stuff. I went from a 105k btu oil furnace to a 60k btu 2 stage and it sounds like I got screwed !

I cant imange even in the winter this will fire at hi stage when it only has to go up a deg or 2. The temp rise is right wher it should be both hi and low fire

[beenthere]

i may be wrong but i believe they are both stageing furnaces. York just has more stages then the others.

I believe lennox is the only one that has a true modulating gas valve and the rest are staging.

like i said i could be wrong

So the Lennox has infinitely varing manifold pressure?

At 65 steps, The York modulates.

[beenthere]

If you are comfortable having cold air blowing out of your registers and the highest gas bill on the block either one will work.
Haven't had cold air blowing out the registers of any York mod.(ok, the one that the trap cracked on it did when it went into failure)

Replaced a 90% (won't mention the brand)with a York 95% mod, and his gas bill is lower. And his house has a more even temp through out.

[beenthere]

Would a typical installer setup the system, for GAS heat only in the high stage assuming the outside temp has already passed the need for 30KBTUh?

One of the concerns I had was when the system changes over to Gas, will the furnace start at low fire and take awhile to figure out it really needs to be medium or high....

Also, since the Sales people who have sent quotes don't really beleive in Manual J I did my own 36K gain / 88K loss Should I expect the HP to be sized higher than 3 Ton?

No, the HP's BTU output will be less then the furnaces low fire output at the switch over point. So the furnace sarting in low fire is still going ot be able to heat the house at balance point.

What was the sensible and latent load, and what were the design temps you used.

[beenthere]

[QUOTE=cpetku;2008275]Based upon my final loss (80K) and load (34K Sensible) numbers and the feedback in this thread I believe the following systems will meet my needs better than the original proposals

Sys #1 Bryant 355BAV 100K in (not CAV) and 286 4 Ton 16 Seer HP
Sys #2 York 2 Stage Affinity 100K in and 18 Seer HP (9.8 HSPF is the deciding factor)

QUOTE]

Are you really looking at the Affinity YZH, or the Affinity YZE heat pump.
You won't get a return on the YZH over the YZE.

[cvcman]

beenthere, whats your view point on this ? Is my Rheem RGRL 2 stage really running at less than 50% efficiency in low stage ?? This is where mine runs in this type of weather 98% of the time ?

If this is the case someone is going to get a knot on their head ! I will have them take it out and put in a single stage if this is right. How do you know for sure what efficiency it is at low fire ?

This was NEVER explained to me nor have I ever heard this before......

I feel like I got boned, it seems like a 60K btu for my 1100 sf home is right and every company told me the same thing:mad:

[tinknocker service tech]

if these companys selling these units do not tell their customers that these are 50% efficient running at low stage I would think they can be held liable.

Mine always fires and runs at low UNLESS it has to raise the temp more han 2 degs which the only time it does this is after a setback of 5 degs at night. Then it goes to high.

I have only had it 3 months so not an real cold weather yet but im thinking of calling the company Monday now that I hear this stuff. I went from a 105k btu oil furnace to a 60k btu 2 stage and it sounds like I got screwed !

I cant imange even in the winter this will fire at hi stage when it only has to go up a deg or 2. The temp rise is right wher it should be both hi and low fire



Just because your oil fired furnace was rated for 105.000 btu does not mean it was fireing at that. It is not uncommon for an oil burner to be down rate and may have been fireing at 80,000 btu
you load calc may ave come to 60,000 btu total.
i dout very much you git screwed. The unit is handling the load it is under and in low fire now as the load increases it will go to high or low depending on set up.
sounds like it is doing what it is designed to do
see how things go first

[cvcman]

it already seems as though with only about 15 cycles of 10 mins each it has used 3 therms of gas. At this rate if it fires 2 cycles per hour in cold weather for a 24 hr period I will use 460.00 a month in gas !

Thats HUGE for a 1100 sf house. Also WHY would I want a furnace that is supposed to be very efficent but it runs most of the time at low stage and I am told here low stage is less than 50% efficient, I got boned !:mad:

[hvaclover]

beenthere ......

I feel like I got boned, it seems like a 60K btu for my 1100 sf home is right and every company told me the same thing:mad:

Went back stage afterall:confused:?

[beenthere]

it already seems as though with only about 15 cycles of 10 mins each it has used 3 therms of gas. At this rate if it fires 2 cycles per hour in cold weather for a 24 hr period I will use 460.00 a month in gas !



A 60,000 BTU input furnace, would have to run for 5 hours to use 3 therms.

So either it ran a lot more then 15 cycles of 10 minutes (which would only be 2.5 hours) cycles, or you have a gas leak, or other appliance using gas.

Being yours is 60,000 BTUs, it would have to run 8.3 hours in first stage to use 3 therms.

[Jim Davis]

Hi:

Just this month I had a 100Kbtu 80% replaced with a 75Kbtu Rheem mod, model RGJD. What I am reading here is somewhat of a concern. I picked the unit for both efficiency and comfort. Here is what I've observed so far:

The unit is very comfortable, and most of the time you can hardly hear it. I haven't had it long enough, and the temp is mild enough so far, that I don't have a handle on gas usage.

I programmed my home automation controller to read the thermostat PWM signal. When bringing up the house in the morning, the T-stat starts at 100% and ramps down to 40% before shutoff. When cycling to maintain temp, it starts at 60% and ramps down to 40% before shutoff.

Now, my question for Captain CO and RoBoTeq: Do you believe the mod or staged furnaces are less efficient on low-fire due to the furnace itself, or conduction loss in the ductwork because the furnace spends more time on? As an engineer, I'm interested in as much detail as you are comfortable providing.

Thanks, Larry

Good I know you might undertand this. Burners heat heat exchangers. 60% of the heat generated is by radiant heat. If you reduce the flame size the flame is farther from the heat exchanger and makes the heat exchanger less hot. No different than moving your hand away from a candle flame. Therefore the efficiency of heat transfer is greatly reduced. Then the rest of the heat exchanger has to be scrubbed with the gasses produced by combustion. It is hard to scrub a 100,000 btu heat exchanger with 60,000 btus. It would be like putting a 2-cylinder engine in a van and expecting to get better milage because you drive slow. The weight of the van doesn't change.

[cvcman]

beenthere, at your cals then in cold weather if mine runs every 1/2 hr for 15 mins then in a full day it will run 12 hrs, then it would use 4 therms a day right ?

Thats still alot but not as many as im calculating. I clocked the dial on the meter that moves the fastest, on hi fire it took 25 secs to go around one time, low fire about 47 secs.

There has to be a way to see for sure unless I zero my filter minder on the stat, take an exact reading then let it run for a few day like this then see.

At any rate IF Jm is right it doesnt matter,he said I would have the highest gas bill on the block and use 40% more gas with a 2 stage firing at low whih again is where mine seems to run...

Thank you for trying to help me

[hvaclover]

beenthere, at your cals then in cold weather if mine runs every 1/2 hr for 15 mins then in a full day it will run 12 hrs, then it would use 4 therms a day right ?

Thats still alot but not as many as im calculating. I clocked the dial on the meter that moves the fastest, on hi fire it took 25 secs to go around one time, low fire about 47 secs.

There has to be a way to see for sure unless I zero my filter minder on the stat, take an exact reading then let it run for a few day like this then see.

At any rate IF Jm is right it doesnt matter,he said I would have the highest gas bill on the block and use 40% more gas with a 2 stage firing at low whih again is where mine seems to run...

Thank you for trying to help me


Gee dude. That sucks.

[beenthere]

It would be like putting a 2-cylinder engine in a van and expecting to get better milage because you drive slow. The weight of the van doesn't change.

Funny you should use that anology.

A tune up shop near me. Does't engining tuning to factory specs(not the PM tune up most of us are use to).

He does a dyno test on each one.
It took 56 HP to get a mini van that weighed XXXX pounds(don't remember the exact weigh) at 55 miles per hour on the dyno.
He said on the road, it will take more though, due to wind resistance.

The van weight didn't change, but the HP required to do the work in real life conditions did.

PS: His average charge for one of these tune ups, was $650.00, and thats not a typo.

[beenthere]

At any rate IF Jm is right it doesnt matter,he said I would have the highest gas bill on the block and use 40% more gas with a 2 stage firing at low whih again is where mine seems to run...

Thank you for trying to help me

I respect Jim.

But don't buy everything he says.
There are too many 2 stage furnaces saving money over the 80% furnaces that they replaced.

If it were true that a 2 stage 90% furnace is only 40% efficient in first stage.
Then the 80% furnaces they replaced would have had to of been less then 30% efficient by the savings that people see.

Next, you can't use a set run time to calculate how much fuel you will use.
Since your not on a set time for it to go to second stage, or shut off.
Your stat uses temp differencial for operation, not time.

[Jim Davis]

I respect Jim.

But don't buy everything he says.
There are too many 2 stage furnaces saving money over the 80% furnaces that they replaced.

If it were true that a 2 stage 90% furnace is only 40% efficient in first stage.
Then the 80% furnaces they replaced would have had to of been less then 30% efficient by the savings that people see.

Next, you can't use a set run time to calculate how much fuel you will use.
Since your not on a set time for it to go to second stage, or shut off.
Your stat uses temp differencial for operation, not time.

I said a 2-stage furnace runs less than 50% in low fire. Most 80% furnaces run less than 65% in the field in high fire so yes even a 90% will save money over them no matter how bad they run, but not the 40% that people should be seeing. Efficiency is efficiency regardless of run time. CFM X Delta T tells us how many btus are being delivered to the air. Look at the input and the efficiency is easy to calculate. One must measure static pressure in order to use the manufacturers blower spec sheets.

[hvaclover]

Been I ain't the sharpes knife in the drawer, but I do enrgy audits for my customers comparing the energy consumption over a three to five year period.

It's diffacult cause you have consider rate increases and the amount of cold days in one year vs another. In every case our installs have brought down the gas bill on average of 35%,

I was going to get into combustion testing but I have not been able to get an anser from Jim Davis on a basic fundemental: If you test a furnace and the reading are off how do you make adjustments since there are no more air shutter on burners thede days.

[Freezeking2000]

Based on what I have read on this subject if you have an uninsualted and leaing duct system located outside the conditioned space you will have trouble with a modulating furnace using more fuel than a conventional furnace. If the same duct system is in the basement the leakage wold help heat the home. I still do believe a new or a tight duct system, properly installed with r-6 or r-8 insulation is a great fit for a modulating furnace. I think this could go with a retrofit to a dual fuel system as well since the run times will be increased. We do have to do a better job selling duct sealing on modulating and dual fuel applications.

[cvcman]

Ok Rheem told me that seeing as how I am running a 2 stage stat and if the temp drops 1 deg and fires the furnace it will fire in low stage and will NOT switch to hi unless it sees the temp drop while in low and he said i doesnt matter how long it runs even IF it doesnt raise the temp even 1 deg it will run forever in low stage.

Now I have read here that after so many minutes it will go to hi. He said it will not unless you are running a single stage stat???

Who is correct:mad:

[beenthere]

Ok Rheem told me that seeing as how I am running a 2 stage stat and if the temp drops 1 deg and fires the furnace it will fire in low stage and will NOT switch to hi unless it sees the temp drop while in low and he said i doesnt matter how long it runs even IF it doesnt raise the temp even 1 deg it will run forever in low stage.

Now I have read here that after so many minutes it will go to hi. He said it will not unless you are running a single stage stat???

Who is correct:mad:
Your furnace isn't using the timer, so it depends on your thermostat. On what criteria has to be met to go to second stage.

[mayguy]

it will fire in low stage and will NOT switch to hi unless it sees the temp drop while in low and he said i doesnt matter how long it runs even IF it doesnt raise the temp even 1 deg it will run forever in low stage.

Who is correct:mad:

He's correct. On mine when we get say -15˚, the furnace will run non stop in 1st stage, and the t-stat will cycle into 2nd stage as needed.

A couple of years ago, we had 3-4 days of -20˚, and the furnace never shut down. (Had t-stat on Hold)

[cvcman]

sorry I guess im going to 2 diff posts again... So that being said me having a 2 stage furnace is a waste it will always run in low stage unless its after a set back. this is crap man they never told me this and I am not happy to say the least !:mad:

[beenthere]

Been I ain't the sharpes knife in the drawer, but I do enrgy audits for my customers comparing the energy consumption over a three to five year period.

It's diffacult cause you have consider rate increases and the amount of cold days in one year vs another. In every case our installs have brought down the gas bill on average of 35%,

I was going to get into combustion testing but I have not been able to get an anser from Jim Davis on a basic fundemental: If you test a furnace and the reading are off how do you make adjustments since there are no more air shutter on burners thede days.

Gas pressure, and blower CFM are what you have to adjust.(there are a few other things, but not in this open forum).

Keep in mind, that the longer the flue and vent pipe are, the less air the induce can draw in, that effects combustion efficiency. So you adjust the gas pressure to compensate for the flue and vent pipe.

Also. You need to adjust the CFM for temp rise. Too much air, and you cool down the HX too much to get good heat transfer. Not enough, and you get a real hot HX, but put more heat out the flue then needed.

The install manual might say x.x" manifold pressure for first stage. But that is based on xxxx BTU per CF of gas. And many areas have more, or less BTU content then the manufacturer uses for their test. So you may have to adjust it up or down a couple tenth of an inch to get proper rise.


AFUE, and SSE are not the same thing.

[beenthere]

sorry I guess im going to 2 diff posts again... So that being said me having a 2 stage furnace is a waste it will always run in low stage unless its after a set back. this is crap man they never told me this and I am not happy to say the least !:mad:
No its not.

You are just getting too much conflicting info, and worrying about more then you should.

And, I believe we did say that 2 stage is for comfort, in your post before you got your new furnace.

Relax. Use it set this way for a few months, and see how it works. You may be far more pleased with it then. Right now, your worring too much, to be able to be happy with any explanations you get.

There are stats that can forse it into second stage by time.
EG: After 20 minutes if stat is still calling it would go to second stage.

A lot of people like that, and a lot don't.
The ones that don't like it, don't like when it goes to second stage for 1 minute and then shuts off.

You have an efficient comfort system.

Enjoy it. Don't get tunnel vision on numbers. They can lead you astray, in how your system will really operate.

[beenthere]

He's correct. On mine when we get say -15˚, the furnace will run non stop in 1st stage, and the t-stat will cycle into 2nd stage as needed.

A couple of years ago, we had 3-4 days of -20˚, and the furnace never shut down. (Had t-stat on Hold)
Most thermostats can be set to statisfy in second stage instead of cycling from first ot second back to first again.

[mayguy]

sorry I guess im going to 2 diff posts again... So that being said me having a 2 stage furnace is a waste it will always run in low stage unless its after a set back. this is crap man they never told me this and I am not happy to say the least !:mad:

No, it's not a waste.. It's COMFORT, and quiet! I'd rather have a furnace that can run quiet.. (Mine is about 8' away from me in the family room down here)

When it get at design temp, then 2nd stage is going to run more often.

[mayguy]

Most thermostats can be set to statisfy in second stage instead of cycling from first ot second back to first again.

Correct, but I'd rather have it cycle back and forth.

[beenthere]

Correct, but I'd rather have it cycle back and forth.
Yes, and for you, you want a high comfort level.

cvcman, is looking more for efficiency, and may not have been aware from your post that its possible to have them satisfy in second stage if so desired. :)

[RoBoTeq]

Hi:

Just this month I had a 100Kbtu 80% replaced with a 75Kbtu Rheem mod, model RGJD. What I am reading here is somewhat of a concern. I picked the unit for both efficiency and comfort. Here is what I've observed so far:

The unit is very comfortable, and most of the time you can hardly hear it. I haven't had it long enough, and the temp is mild enough so far, that I don't have a handle on gas usage.

I programmed my home automation controller to read the thermostat PWM signal. When bringing up the house in the morning, the T-stat starts at 100% and ramps down to 40% before shutoff. When cycling to maintain temp, it starts at 60% and ramps down to 40% before shutoff.

Now, my question for Captain CO and RoBoTeq: Do you believe the mod or staged furnaces are less efficient on low-fire due to the furnace itself, or conduction loss in the ductwork because the furnace spends more time on? As an engineer, I'm interested in as much detail as you are comfortable providing.

Thanks, Larry
The efficiency loss is due to the thermal transfer of heat through the metal heat exchanger. When a heat exchanger is designed to transfer 95% of the heat produced through a certain amount of heat exchanger wall area at a certain temperature, then reducing the amount of Btu's of heat in that same space simply will not transfer the same percentage of heat through the walls of the heat exchanger. However; this reduction in heat transfer under properly operating conditions is no where near as low as Jim is inferring.

Single staged furnaces would simply short cycle more often which also decreases the rated efficiency of the furnace. Furnace efficiencies are rated at their peak performance in test labs under ideal conditions. Since all furnaces are rated this way, all furnaces are rated fairly. This does not mean that your furnace is going to always operate at peak efficiency in your home. Efficiency ratings is just a number determined during optimum conditions. When was the last time a vehicle you owned got anywhere near the gas mileage claimed by the manufacturer?

The Rheem/Ruud modulating furnace has been my personal favorite furnace for years. Now that other brands have come out with modulating furnaces, I may have other favorites to choose from. As with all staged furnaces, the Rheem modulating furnace is designed to operate as long as possible under the least amount of required heat to do the job keeping the home comfortable.

Because staged furnaces operate longer cycles, they do not waste fuel during as many warm up periods. All furnaces are very inneficient during the initial warm up of the heat exchanger. By keeping the heat exchanger warm longer, staged furnaces make up the difference in efficiency loss from low fire by not having to continually warm up the heat exchanger over and over again.

So, while low fire on staged furnaces may by itself be tested to be less efficient (50% is an extreme where something other then the furnace design was at fault), the efficiency loss on a properly sized furnace is still no greater then the efficiency loss on a single stage furnace cycling more often.

You guys really need to stop letting the Captain of Doom and Gloom scare you:rolleyes:

[RoBoTeq]

if these companys selling these units do not tell their customers that these are 50% efficient running at low stage I would think they can be held liable.

Mine always fires and runs at low UNLESS it has to raise the temp more han 2 degs which the only time it does this is after a setback of 5 degs at night. Then it goes to high.

I have only had it 3 months so not an real cold weather yet but im thinking of calling the company Monday now that I hear this stuff. I went from a 105k btu oil furnace to a 60k btu 2 stage and it sounds like I got screwed !

I cant imange even in the winter this will fire at hi stage when it only has to go up a deg or 2. The temp rise is right wher it should be both hi and low fire
Oh for crying out loud; let go of the Captain's 50% scare tactics! If all you are doing is looking for reasons to sue, then get Captain CO to go to court with you. Your furnace has been rated to a specific efficiency and under the conditions of the ratings it will perform those efficiencies. Since all furnaces are rated under the same regulations, your furnace is exactly what the manufacturer claims it to be under the conditions of the rating testing.

Yes! Jim is not lying. I have the utmost respect for Jim's knowledge and abilities. However, that guy on those Ginsu commercials is also not lying when he slices through rotten tomatoes and whipped cream with that knife that you haven't got a shot of being as good with when you get it home.

[hvaclover]

Gas pressure, and blower CFM are what you have to adjust.(there are a few other things, but not in this open forum).

Keep in mind, that the longer the flue and vent pipe are, the less air the induce can draw in, that effects combustion efficiency. So you adjust the gas pressure to compensate for the flue and vent pipe.

Also. You need to adjust the CFM for temp rise. Too much air, and you cool down the HX too much to get good heat transfer. Not enough, and you get a real hot HX, but put more heat out the flue then needed.

The install manual might say x.x" manifold pressure for first stage. But that is based on xxxx BTU per CF of gas. And many areas have more, or less BTU content then the manufacturer uses for their test. So you may have to adjust it up or down a couple tenth of an inch to get proper rise.


AFUE, and SSE are not the same thing.

Ok thanks for being helpful. Dang Some guys act like combustion science is some arcane art that you need to join a secret society to learn.

Well its good to know that I probably got a pretty hadle on the fundamentals so if I sign up for a course it won't be so tough for an older guy.

[beenthere]

Ok thanks for being helpful. Dang Some guys act like combustion science is some arcane art that you need to join a secret society to learn.



LOL...

I know. Its strange how they will tell you how to check and adjust the charge of an A/C or HP, but ask about combustion. And its clam up time.

I can understand they might feel loyalty to Jim, and want him to make money.
But, then you would think they would not answer questions about anything else either, since there are schools and seminars for everything else also.


Some day, I may join that secret society. LOL

[hvaclover]

A member of my RSES chapter has subed for Jim davis (or so he says. I guess they are friends) and I know that guy is a combustion expert.

But we seem to have a controversy going now ,that caveman guy or what ever his name is, thinks he got boned and I think a lot of guys are starting to wonder what really is true or hype.

[hvaclover]

And a joint would be good about now (check the spelling in the las line of your reply:cool:).

[beenthere]

There is a slight drop in steady state combustion efficiency in first stage.
A CA can only tell you combustion efficiency, not total heat transfer efficiency.

Total heat transfer efficiency is effected by everything hooked to the system that effects air flow. Including return air temp.

A furnace is more efficient with a return air temp of 50°F, then it is with a return air temp of 85°F.

I tore out a 90% single stage, and installed a York 95% mod. It uses less gas for the year then the single stage did(which did supprise me).

It does seem to use a little more on some of the milder months(but the daughter was
home from college those months).
Other then when it was commisioned, its never been at full modulation(we're having warm winters for the last 3 years now).
And the gas usage is being compared to the first warm winter, which was the last winter the single stage was used.

I don't think the question should be how efficienct is a 90% furnace, But more, how efficient will the install situation/set up allow it to be.

A 80% with proper duct and register throw will use less gas the a 90% riding the high limit because of undersized duct work.

[beenthere]

And a joint would be good about now (check the spelling in the las line of your reply:cool:).
ROFL. :D

I fixed it.

[cvcman]

beenthere, I tapped EVERY joint on my duct work both hot and cold with metal duct tape. They are in my basement so maybe it didnt need to be done but it shouldn't do any harm right ? I was only going to do the cold air so it didnt suck any air from the basement but I did the hot also.

These ducts seem big, house built in 1955 all galv metal duct . Thx again for the help and the Valium:D

[beenthere]

Sealing the joints won't hurt.

I'm ready for another Coors Light. :)

[cvcman]

another, how many times you gonna be up tonight getting rid of it ?? Im gonna watch Boston Legal at 10 and hit the sack.

Hey do you think my neighbors boiler uses lees gas than my furnace ? He has the same size house with an 82% boiler. It seems like with these hot water baseboard heat syatems your floors are always cold and you have to be carefull where you put your furniture so you dont block it.

I have heard they are the best for efficiency.

See ys Coors man;)

[beenthere]

Hopefully no more then once. :)

Can't say from here if he will use more or less for sure.

[cvcman]

once is good, wait till you get older... he claims his boiler is the most efficient way to heat.

Any reasons my floors seem colder than when i had the oil ?

probably the oil furnace heated up the basement more

[davidr]

LOL...

I know. Its strange how they will tell you how to check and adjust the charge of an A/C or HP, but ask about combustion. And its clam up time.

I can understand they might feel loyalty to Jim, and want him to make money.
But, then you would think they would not answer questions about anything else either, since there are schools and seminars for everything else also.


Some day, I may join that secret society. LOL

Overcharging or undercharging a condensor or HP never killed anybody.

Screw up a piece of combustion equipment without all the other parameters being set and all bets are off.
Recommend a HO seals his ducts on a system that nothing is known about, telling them it's okay, and you could create conditions that might make an appliance spill or crack the heat exchanger as the duct leakage was the only way the furnace was moving enough air.

We can barely teach what's required to do combustion testing and diagnostics properly in a three day class.
It's not going to happen over an internet forum which is what it appears a lot of guys want.

There is a lot to the combustion side of this, a lot more than just setting gas pressure and delta T within range.
A lot more than should be covered in the residential section of HVAC Talk.

Being helpful is one thing, overstepping our bounds is another.

[beenthere]

Overcharging or undercharging a condensor or HP never killed anybody.

Screw up a piece of combustion equipment without all the other parameters being set and all bets are off.

Basically. Most furnaces installed are installed without all other parameters being set.

We can barely teach what's required to do combustion testing and diagnostics properly in a three day class.

I didn't know you were one of the instructors.


Recommend a HO seals his ducts on a system that nothing is known about, telling them it's okay, and you could create conditions that might make an appliance spill or crack the heat exchanger as the duct leakage was the only way the furnace was moving enough air.

.

Furnace is his only gas appliance.

[cvcman]

for real ??, sealing my ducts from small seams is going to crack my HE, my temp rise in low fire was about 48 ??? I have 7 hot air runs and 5 cold air ...:rolleyes:

[beenthere]

for real ??, sealing my ducts from small seams is going to crack my HE, my temp rise in low fire was about 48 ??? I have 7 hot air runs and 5 cold air ...:rolleyes:

Nope, it won't.

If you want. After your 5 hour gas use test is done.
Run your system in second stage and recheck your temp rise.

[cvcman]

is the hi fire test more important than low fire ?? I can do it in the morning as it goes to h fire after set back,,,,this may screw up my test for therms used too:confused:

Oh well i will check the temp rise again in the morning:D

[beenthere]

Temp rise should be checked in both stages.

[hvaclover]

There is a slight drop in steady state combustion efficiency in first stage.
A CA can only tell you combustion efficiency, not total heat transfer efficiency.

Total heat transfer efficiency is effected by everything hooked to the system that effects air flow. Including return air temp.

A furnace is more efficient with a return air temp of 50°F, then it is with a return air temp of 85°F.

I tore out a 90% single stage, and installed a York 95% mod. It uses less gas for the year then the single stage did(which did surprise me).

It does seem to use a little more on some of the milder months(but the daughter was
home from college those months).
Other then when it was commisioned, its never been at full modulation(we're having warm winters for the last 3 years now).
And the gas usage is being compared to the first warm winter, which was the last winter the single stage was used.

I don't think the question should be how efficient is a 90% furnace, But more, how efficient will the install situation/set up allow it to be.

A 80% with proper duct and register throw will use less gas the a 90% riding the high limit because of undersized duct work.

You know what you say is very true and very basic. Maybe I am revealing an old school attitude, but it seems since all the whiz bang efficiency starting with the first faulty 80%ers back in the 1970s, to the now cutting edge staged and modulating science, we have let the technology override our common sense and make us rely more on the machine then our own hvac education.

[beenthere]

I won't say common sense has gone out the window.
Its just getting harder to interphase new tech with common sense.

Now we have. Combustion efficiency(SSE), AFUE, EER, SEER, COP, HSPF, IBR, DOE efficiency ratings.

We need to keep all those straight, know how they come up with them, and still know how to turn wrench.

No wonder I'm bald and gray. :) LOL

[hvaclover]

I won't say common sense has gone out the window.
Its just getting harder to interphase new tech with common sense.

Now we have. Combustion efficiency(SSE), AFUE, EER, SEER, COP, HSPF, IBR, DOE efficiency ratings.

We need to keep all those straight, know how they come up with them, and still know how to turn wrench.

No wonder I'm bald and gray. :) LOL

Then i was right ; it is an old school attitude. :D You just said it better than I did.

[cvcman]

did the check after 5 mins on hi fire, 120 and 68 so it looks like 52 deg temp rise. I checked low fire the other day and it was like 40 ish

I took these right at the plenum above the acoil and right after the filter before the blower with a digital thermom

[hvaclover]

did the check after 5 mins on hi fire, 120 and 68 so it looks like 52 deg temp rise. I checked low fire the other day and it was like 40 ish

I took these right at the plenum above the acoil and right after the filter before the blower with a digital thermom

120* in my book is perfect. Now if you could find out the btu content of a cu ft of NG for your area you could clock the meter and determine the riring rate of the furnace.

[davidr]

Furnace is his only gas appliance.

Couldn't get the rest of that to quote. :D

Just because those other parameters aren't known doesn't make it acceptable to base assumptions off of.

That is the whole reason manufacturers try to make the equipment idiot proof, they know more than likely who's going to be installing it.

If the guys who installed it were as knowledgeable as you been the manufacturers wouldn't have to worry about those issues.

Yes I am now one of the instructors, and you know what I am getting at with the duct sealing. ;)

Did I miss anything? :D

[cvcman]

Nyseg said when I read the meter if the needle is past number 1 it is one threm because the meter reads in ccf or something like that and when you get the bill its in therms and the conversion is one for one aprox.

This is what the bill say " 3 ccf " energy content factor X 1.021900

So 3 X 1.021900 = 3.006 therms :confused:

Now my basic service chg includes 3 free therms so bill for usage is zero.

$13.00 meter fee per month.

I did the low fire again and it is like 43 temp rise. This is with a digital oven thermometer:o

[hvaclover]

Nyseg said when I read the meter if the needle is past number 1 it is one threm because the meter reads in ccf or something like that and when you get the bill its in therms and the conversion is one for one aprox.

This is what the bill say " 3 ccf " energy content factor X 1.021900

So 3 X 1.021900 = 3.006 therms :confused:

Now my basic service chg includes 3 free therms so bill for usage is zero.

$13.00 meter fee per month.

I did the low fire again and it is like 43 temp rise. This is with a digital oven thermometer:o

LOL...sounds like Emril Lagase the chef working on his furnace.

Think you better use something a little more geared towards HVAC accuracy.

[cvcman]

probably but its all I got right now Im waiting for my HVAC license from Twilli's mail order house. I have logged over 500 hrs on this site so far;)

That thermometer is very accurate though. I wonder how good those digital infared hand helds are?

I could use them for alot of things:rolleyes:

[hvaclover]

probably but its all I got right now Im waiting for my HVAC license from Twilli's mail order house. I have logged over 500 hrs on this site so far;)

That thermometer is very accurate though. I wonder how good those digital infared hand helds are?

I could use them for alot of things:rolleyes:

Don't take one to a Gentlmans Club what ever you do.

I got banned from Jon-Jon's for using a CPS IR gun for using it to find the girl's "HOT" spots:o

[RoBoTeq]

Don't take one to a Gentlmans Club what ever you do.

I got banned from Jon-Jon's for using a CPS IR gun for using it to find the girl's "HOT" spots:o
You need a thermometer to determine where a naked woman's hot spot is?:confused::rolleyes:

[hvaclover]

You need a thermometer to determine where a naked woman's hot spot is?:confused::rolleyes:

Do I need to explain it or are you just warming up to kick my butt again:confused::eek::confused::D

[RoBoTeq]

Do I need to explain it or are you just warming up to kick my butt again:confused::eek::confused::D
Actually, I'd better back off on this one so I don't get myself banned:D

Photos would have helped:p

[beenthere]

Yes I am now one of the instructors, and you know what I am getting at with the duct sealing. ;)

:D

Congrats.

You may have missed that I have had email correspondence with cvcman about his furnace and set up that is not posted in the threads. Starting back when he was trying to deide which furnace to get.

No, I wasn't actually at his house though. :)

And yes, I do know what you were getting at about blindly sealing the ducts.

[hvaclover]

Congrats.

You may have missed that I have had email correspondence with cvcman about his furnace and set up that is not posted in the threads. Starting back when he was trying to deide which furnace to get.

No, I wasn't actually at his house though. :)

And yes, I do know what you were getting at about blindly sealing the ducts.

Oh no! Been is doing side jobs!!:eek:

[hvaclover]

Actually, I'd better back off on this one so I don't get myself banned:D

Photos would have helped:p

What's funny is this incident happened ove ten years ago.

I went there with a helper last year and I was still banned!

[beenthere]

Oh no! Been is doing side jobs!!:eek:
ROFL. :)

[RoBoTeq]

What's funny is this incident happened ove ten years ago.

I went there with a helper last year and I was still banned!
You sure you were using a laser and not an immersion probe?

[hvaclover]

You sure you were using a laser and not an immersion probe?

Kinda fuzzy...was drinking and taking pain pills back then.....Crap I got laid and don't rmember?:o

[Ben Around]

I am going to stay away from this. I do not believe for a minute that a 97.5 furnace will run at 50%. I do not believe a combustion test can show proper readings on modulating furnaces if thats the case.

The new York. Luxaire vary the blower motor on all models, not just using 2 or 3 speeds either. Also the induced draft motor varies as well.

Do not believe this thread.................!

I Agree, Someone is confused.

The spec sheet on my Rheem Prestige (RGFD) modulating says;

Input Max 90,000 BTU/HR -Heating Capacity max 86000 BTU?HR = 95% efcy

Input Min 36,000 BTU/HR -Heating Capacity min 33,840 BTU?HR = 94% efcy

40 % gas on low setting but still getting 90 +

[RoBoTeq]

I Agree, Someone is confused.

The spec sheet on my Rheem Prestige (RGFD) modulating says;

Input Max 90,000 BTU/HR -Heating Capacity max 86000 BTU?HR = 95% efcy

Input Min 36,000 BTU/HR -Heating Capacity min 33,840 BTU?HR = 94% efcy

40 % gas on low setting but still getting 90 +
Please understand that these are ratings. Just like the automotive industry MPG ratings, furnace ratings are all achieved under absolute maximum conditions.

Since there is no way to duplicate testing conditions in the field (your home), your furnace is not likely to achieve the rated efficiency. However; since all furnaces are rated equally, the percentage of efficiency difference will be the same between furnaces in your home as they are in the testing labs.

Under extreme conditions, a 95% furnace could operate at 50%, but this is no more a reality of the conditions of furnaces out of the box then the test ratings are.

[Ben Around]

Please understand that these are ratings. Just like the automotive industry MPG ratings, furnace ratings are all achieved under absolute maximum conditions.

Since there is no way to duplicate testing conditions in the field (your home), your furnace is not likely to achieve the rated efficiency. However; since all furnaces are rated equally, the percentage of efficiency difference will be the same between furnaces in your home as they are in the testing labs.

Under extreme conditions, a 95% furnace could operate at 50%, but this is no more a reality of the conditions of furnaces out of the box then the test ratings are.
I understand ratings, I was an automotive engineer.

These manufacutrers' ratings tell me the furnace is designed to get;
95% efficiency at 100% gas flow and
94% efficiency at 40% gas flow.

How do you come up with a scenerio that it could get down to 50% efficiency at a low flow if it remains within the range on the spec sheet?

(No offense but I am Just here to learn)

[hvaclover]

Get ready for another 300 posts on this thread people.

We got us an engineer asking questiosn:cool:

Just fuunin' ya guy, both my kids are engineers and i am real proud of them.

[beenthere]

Get ready for another 300 posts on this thread people.



If this thread wasn't too long already, I would get it moving again.

[hvaclover]

If this thread wasn't too long already, I would get it moving again.

What're ya tryin' to do beat Davidr and Time builders all time record?

You one clazy whiteboy lolololol

[beenthere]

What're ya tryin' to do beat Davidr and Time builders all time record?

You one clazy whiteboy lolololol
naw, I'm gonna let this thread die. :D

[hvaclover]

naw, I'm gonna let this thread die. :D

Here..leme help..




kaBLAMMM..dman it! Missed...!

[RoBoTeq]

I understand ratings, I was an automotive engineer.

These manufacutrers' ratings tell me the furnace is designed to get;
95% efficiency at 100% gas flow and
94% efficiency at 40% gas flow.

How do you come up with a scenerio that it could get down to 50% efficiency at a low flow if it remains within the range on the spec sheet?

(No offense but I am Just here to learn)
I'm just not sure how to explain it any better then I already did. I can take no offense just because you don't understand what I post. Real life applications are not the same as rating test applications. Maybe since you are an engineer you live in a test lab and this doesn't apply to you.

[House]

I'm just not sure how to explain it any better then I already did. I can take no offense just because you don't understand what I post. Real life applications are not the same as rating test applications. Maybe since you are an engineer you live in a test lab and this doesn't apply to you.

Perhaps some pro could post results of two HSER tests of an anonymous home with a
multi-stage furnace running in low and high fire.

[RoBoTeq]

Perhaps some pro could post results of two HSER tests of an anonymous home with a
multi-stage furnace running in low and high fire.
What good would that do? Unless every parameter affecting the outcome were inspected and determined how each specific factor affected the testing, it would be a virtually useless test.

If your existing home has a 60% rated efficiency furnace (not old methods of rating furnaces by bonnet efficiency) and your new furnace is 95% rated effiency, then under the application parameters of your specific home you can expect to have about a 37% decrease in your gas usage.

[davidr]

What good would that do? Unless every parameter affecting the outcome were inspected and determined how each specific factor affected the testing, it would be a virtually useless test.

If your existing home has a 60% rated efficiency furnace (not old methods of rating furnaces by bonnet efficiency) and your new furnace is 95% rated effiency, then under the application parameters of your specific home you can expect to have about a 37% decrease in your gas usage.

I think he's referring to comparing delivered BTUs with equipment rated BTUs Robin.

[RoBoTeq]

I think he's referring to comparing delivered BTUs with equipment rated BTUs Robin.
I understand that. Still, if I am the one doing the test and I test the equipment before it reaches it's peak performance level, I have a low temperature rise, my gas Btu rate is lower then average and my venting has issues; I am going to record a low Btu output compared to the rated Btu's. However; I am going to have the same results no matter what furnace I install. It is the conditions that are the problem, not the manufacturing of the furnaces. This is where training programs such as NCI does can make a good installing contractor a better overall contractor for the consumer.

[DeltaT]

Here's my very unofficial, uneducated and unscientific way I have handled just about all the two stage set-up's I've been asked to work on. No modulating yet but may have one in the basket this week!

I have converted the two state thermostats back to the one stage -where applicable - setting so that the factory internal timer triggers the second stage on.

This has eliminated the HO calls of a chilly house or cold room air sensations.

What I have noticed is that in mild weather there is more of a chance the low fire will take care of the heating load & cycle the T'Stat off before the factory timer switches to hi stage.

As it gets colder then the furnace has more a tendency to run on low, swith to hi, run a little more until set point is met. Then the furnace cycles off and waits for the next call for heat.

When it's cold, really cold, the furnace eventually cycles to high and stays there for a good while till set point is reached.

Having a two stage TStat operate the low and hi of these types of furnaces has been the result of numberous "my house feels cold" calls so this troubles shooting method is not base on energy efficience but to solve a home owners complaint.

The complaints go away, the customer is happy, I don't know what the efficiency is but I do know that the customers do say, as many as I can remember, that their energy bill decreased with the installation of a two stage furnace. This, of course, could simply be because of the type of the old furnace.

I cringe when I see a two stage T'Stats being used to control a two stage furnace.

[beenthere]

This has eliminated the HO calls of a chilly house or cold room air sensations.



Don't think I ever got a call that the house was chilly from running in first stage using a thermostat that has CPH.

If I get a complaint ofr running too long in first stage, I set the second stage CPH to 2, or 1 number below first stage if first is set to something other then 3.

[RoBoTeq]

So the Lennox has infinitely varing manifold pressure?

At 65 steps, The York modulates.
Actually, it looks like Lennox has 62 stages and York/Luxaire/Coleman have 100 stages at .62 degree intervals. Does this make a difference in comfort? I doubt it. As a matter of fact, I doubt anyone could tell the difference in comfort between Rheem/Ruud's 13 stage modulating furnace and York/Luxaire/Coleman's 100 stage version.

I must say though that after having had the opportunity fo first hand compare a Rheem mod against a Luxaire mod, I now have a new favority gas furnace. The Luxaire is more efficient, much easier to install, work on and set up and I can sell it;)

[hvaclover]

Actually, it looks like Lennox has 62 stages and York/Luxaire/Coleman have 100 stages at .62 degree intervals. Does this make a difference in comfort? I doubt it. As a matter of fact, I doubt anyone could tell the difference in comfort between Rheem/Ruud's 13 stage modulating furnace and York/Luxaire/Coleman's 100 stage version.

I must say though that after having had the opportunity fo first hand compare a Rheem mod against a Luxaire mod, I now have a new favority gas furnace. The Luxaire is more efficient, much easier to install, work on and set up and I can sell it;)

Dang it Robin! What ever happened to the good ol days when;) Goodman was king and you were head of the royal guard? Ah, those battles still ring in my head...:D

[beenthere]

York/Luxaire/Coleman have 100 stages at .62 degree intervals. ;)


That must be a new revision. Use to be 1 degree increments.

[RoBoTeq]

Dang it Robin! What ever happened to the good ol days when;) Goodman was king and you were head of the royal guard? Ah, those battles still ring in my head...:D
Even the entire time I worked for Goodman, I always admitted that the Rheem/Ruud mod was my favorite furnace for comfort. I also made it a point that I was glad it was still expensive and more dificult to install, set up and work on;)

[RoBoTeq]

That must be a new revision. Use to be 1 degree increments.
Very possible. There was a lot of new design information being discussed. Most of which I was not familiar with the past circumstances because I have not been involved with York products.

Interesting that Carrier refers to it's 3 stage furnace as a modulating furnace. I understand that any furnace with more then three stages can be considered modulating. So, would a two stage furnace with a heat pump be considered a modulating hybrid system?

[beenthere]

Interesting that Carrier refers to it's 3 stage furnace as a modulating furnace. I understand that any furnace with more then three stages can be considered modulating. So, would a two stage furnace with a heat pump be considered a modulating hybrid system?

Uh oh. Some one at Carrier may see this thread and decide, YES.

While everyone else will call it a multi stage system. :)

[davidr]

Uh oh. Some one at Carrier may see this thread and decide, YES.

While everyone else will call it a multi stage system. :)

Lol........Copy and paste this thread, if we see the term "modulating hybrid" being used we need to make sure Robin get's his royalties. :D

[hvaclover]

Lol........Copy and paste this thread, if we see the term "modulating hybrid" being used we need to make sure Robin get's his royalties. :D

Barack Obama doing the the Nasty with Hilllary????:confused:

[cvcman]

Hummm.. someone above said that even IF the new furnace wasn't running up to efficiency then even the old one they had wasnt then the customer still saved money...

What if the old furnace was a 80% efficiency but it was 105 k BTU's and the new one is a 90% 60K btus wouldnt the old one heat the house better ie; cheaper ?

There must be a point where bigger IS better than being TOO small:confused:

[RoBoTeq]

Lol........Copy and paste this thread, if we see the term "modulating hybrid" being used we need to make sure Robin get's his royalties. :D
Good to know someone's looking out for me;)

[RoBoTeq]

Barack Obama doing the the Nasty with Hilllary????:confused:
There's always someone who will make a good thing sound really horrible:confused:

[RoBoTeq]

Hummm.. someone above said that even IF the new furnace wasn't running up to efficiency then even the old one they had wasnt then the customer still saved money...

What if the old furnace was a 80% efficiency but it was 105 k BTU's and the new one is a 90% 60K btus wouldnt the old one heat the house better ie; cheaper ?

There must be a point where bigger IS better than being TOO small:confused:
No.

[hvaclover]

There's always someone who will make a good thing sound really horrible:confused:

Liberal:p

[RoBoTeq]

Liberal:p
Oh yea, let's see how liberal you are after watching this; http://www.youtube.com/watch?v=oAUHHoGwow4

[hvaclover]

Oh yea, let's see how liberal you are after watching this; http://www.youtube.com/watch?v=oAUHHoGwow4

That's the modulating hybird I was talking about.:rolleyes:

[cvcman]

I saw this info in with my furnace book, by reading this it sounds like my furnace should fire everytime in hi fire then go to low right ?? It firs in low unless you are bumping the stat over 2 degs.. Let me know if im reading this wrong.
"Individual Board Differences"

90 Plus fires on high speed inducer/high fire, drops to low when a call for low fire is present. 80 Plus fires on low and rises to high fire on a call for second stage. For this reason the boards are not interchangeable (P1 wiring harness connectors are also different and different colors, to prevent mixing the applications.)

[RoBoTeq]

Geez cvc, get a hobby that does not involve staring at your HVAC equipment. Take up drinking or drugs and life will be much nicer for you:rolleyes:

[cvcman]

Thanks for your "insight" I have many hobbys already. I may have a good hobby to suggest for you :eek:

[RoBoTeq]

Thanks for your "insight" I have many hobbys already. I may have a good hobby to suggest for you :eek:
:D touche:D

[beenthere]

I think you have to be standing right beside it to hear it start in high. It drops to low, before the blower comes on.

[cvcman]

Humm maybe, I know when it goes into hi on start up after set back the stat flashes " aux" and "heat" :rolleyes: you can hear it but when it just fires on normal start up it just flashes "Heat"

[beenthere]

Don't confuse stat operation/displays, with built in furnace operations that the stat has no control over.

Since the stat isn't calling for second stage, it won't display that the furnace is using high fire to start. Because the stat isn't energizing the second stage.
And the furnace board is not energizing the W2 terminal when it starts. Its just closing internal relays, that the stat can't sense.

[cvcman]

interesting... so you feel the furnace fires in hi ans switches to low w/i 1 minute before the fan comes on ? Wow, i didnt know that, thanks:D

[beenthere]

Yea.

Some brands start the inducer in high for 15 secs or so. Then drop it to low to begin the rest of the ignition process.

They usually want the inducer to go to full speed for a short period of time, to make sure the bearings are lubricated.
Sleeve bearings require X RPM to start drawing lubrication.
Inducer low speed is not always enough RPM to do this.
So its a way they get better life span from the motor.

I think its Lennox that runs in high until the blower starts.

[mayguy]

I think its Lennox that runs in high until the blower starts.

My Trane XV90 does that.

[beenthere]

My Trane XV90 does that.
Yea. Every brand has their own set up.

I don't know if any one method is really better then the other.

[RoBoTeq]

Periodic high fire is necessary to eliminate condensate issues. Just think what your car or truck would run like if it never had the chance to warm up.

[beenthere]

The York/Luxaire mod has no periodic high fires.

[RoBoTeq]

The York/Luxaire mod has no periodic high fires.
York sucks; Luxaire is great:D

[beenthere]

York sucks; Luxaire is great:D
LOL.. :)

[Freezeking2000]

York sucks; Luxaire is great:D

I agree, all i sell is Luxaire.

[hvaclover]

I agree, all i sell is Luxaire.

What was that...? Did he say Suxaire?

[cpetku]

Is this thread still alive? I tried terminating it at #31 and #40 so now it's time to stir the pot...

I'm looking for one last quote to see if a system replacement makes sense this year before the major brands stop their rebates or if I should buy stock during the current fire-sale and hope it pays for the entire system by the spring.

1) Which of you guys service Clarkston with more than a three tech operation? Who do you rep and are there competitive rebates going on for YOUR brand?

2) Regarding the guys that reply, Who would you others recommend as the best choice for a good design at a competitive/fair price? (this could get really messy as I will only take one more quote before giving up...)

Background:
a) While I have a fair quote on a Bryant 355CAV/286 system, as a DESIGN ENGINEER (oh SH*T) the ARI data seems to imply I should buy a Johnson Controls based unit to get the best performance and maybe save another $100 per year (comment supported by a HVAC PRO).

b) Based upon biases for newer technology (PROS) I should also be looking at Scroll units for good performance at 4 Ton (HVAC PRO) instead of the 286's dual recip.

c) From yet another post we know that I shouldn't need to pay for a liner when we remove the old furnace (HVACLOVER & others).

d) I may also need the return drop increased from a 8X25 to a 10X25 (or wider) based upon furnace manufacturer spec sheets. The only good way to confirm this appears to be by a static test, so you must be willing to do the test

e) Will your quote be based on a loss/gain study? Yours or mine?

Like most HO's I expect value but as a Program Manager/Design Engineer I have made a reasonable estimate on what the cost of the final system should be and the Bryant quote met this gate.

Should you be selected to quote, your recommendation may be shared with your peers, but your price will be held confidential. The only inkling will be if you win the business or if I gamble on the DOW (god knows I can't lose any more).

I assume anyone who knows where and what Jon Jons is also knows where Pine Knob is. Is anyone Hungry or am I violating a rule with this challenge?

[beenthere]

b) Based upon biases for newer technology (PROS) I should also be looking at Scroll units for good performance at 4 Ton (HVAC PRO) instead of the 286's dual recip.


The recip in the 286 is NOT a dual compresser.
Currently, only Trane uses dual compressors for staging in a resi line.

The recip that the 286 uses, is a Twin Single.(Capacity is controlled by direction of rotation)

Depending on your areas humidity, it can do better at humidity control, then the Scroll.

[Ladiesman271]

Thanks Robin. 120* is an ideal I shoot for with a right sized 90% but it is not always atainable because of under size ducts. But I am trying to get a 45* rise which at 120 supply gives me 75* return. Gotta have good ductsizing for that.

Just want the ht ex to last longer than the warranty.



I have a question on that 45* temperature rise. I am thinking about a Thermo Pride gas furnace that uses a 70* temperature rise design as compared with the typical industry 45* rise design. Just wondering if that means the 120* temperature that you use would be increased to about a 140* temperature (68* plus 70* = 138*) if this type of single stage furnace is used.


http://www.thermopride.com/pdfs/Gas-Lit.pdf


Just trying to figure out what brand replacement furnace to buy next year. The second thing I am trying to sort out is the single stage and multi stage thing. That issue is clear as mud as far as operational cost is concerned. The comfort issue is pretty clear.

[hvaclover]

I have a question on that 45* temperature rise. I am thinking about a Thermo Pride gas furnace that uses a 70* temperature rise design as compared with the typical industry 45* rise design. Just wondering if that means the 120* temperature that you use would be increased to about a 140* temperature (68* plus 70* = 138*) if this type of single stage furnace is used.


http://www.thermopride.com/pdfs/Gas-Lit.pdf


Just trying to figure out what brand replacement furnace to buy next year. The second thing I am trying to sort out is the single stage and multi stage thing. That issue is clear as mud as far as operational cost is concerned. The comfort issue is pretty clear.











\\\\\\\\\\\\\\\:D:D:D:D:D:D:D:D:D:D:D///////////////

[RoBoTeq]

I have a question on that 45* temperature rise. I am thinking about a Thermo Pride gas furnace that uses a 70* temperature rise design as compared with the typical industry 45* rise design. Just wondering if that means the 120* temperature that you use would be increased to about a 140* temperature (68* plus 70* = 138*) if this type of single stage furnace is used.


http://www.thermopride.com/pdfs/Gas-Lit.pdf


Just trying to figure out what brand replacement furnace to buy next year. The second thing I am trying to sort out is the single stage and multi stage thing. That issue is clear as mud as far as operational cost is concerned. The comfort issue is pretty clear.
Interesting. There is not enough real data to determine what kind of marketing ploy ThermoPride is using with that 70 degree temperature rise, but, temperature rise should be a range.

Most gas furnaces have a 35-65 degree temperature rise range. You can be sure that the efficiency rating of these furnaces was taken while they were operating at a 35 degree temperature rise when less heat was being put out of the venting. Most contractors strive to hit midway in the temperature rise range with 45-50 degree temperature rise hitting a reasonable comfort/efficiency level while leaving room for a dirty filter to not harm the furnace when the temperature rise may hit the high end of the range.

If 70 degrees is ThermoPride's high end of their temperature rise range, then it is not a significant factor. You should never set up a furnace to run at the high end of the temperature rise range. It is less efficient at that temperature rise and there is no room for error for dirty filters or weakened blower operation.

[Ladiesman271]

I was wondering if that 70* rise claim was just a basic marketing ploy. Thermo Pride equipment is high quality, but I was just trying to figure out what that 70* rise meant in the real world.

I have a 50 year old gas furnace that has a single speed blower. The basic controls are fan and adjustable burner limit switch control (Penn brand). I set the burner temperature limit switch to around 130* years ago for comfort purposes. Those old furnaces seem to work forever with zero service.

The cost of gas has now lower than it was one year ago, so I can wait a bit to swap out the old unit. $500 tax credit in 2009 for energy updates, and nothing for 2008. There is a $400 NSTAR rebate for 90% furnaces with the ECM variable speed blowers, so that is why I am looking into the 2 stage burners. $100 rebate for non ECM blower 90% furnace.

Still not sure if a 2 stage costs less to run than a single stage unit (if in same class).

[beenthere]

Still not sure if a 2 stage costs less to run than a single stage unit (if in same class).

No, it does NOT cost less.

[DanW13]

I think your going to find most power companies are going to start giving rebates on higher effieciency funrace's that only have a ECM Blower motors vs. PCS motors due to the higher engery savings they provide, the same goes for higher seer AC/HP's that have 2 stages of operation for more engery savings. I just recently searched my power companies guide lines for rebates and where there giving the most rebates and what equipment quailifies. This of course takes affect in the coming new year for the rebates on the higher effiency equipment. I can't speak Carrier, Trane, Lennox, and others as far as what rebates there going to be giving in the next 6 months but with a combined rebate from both your local power company and manufacturers you can save enough to possibly buy better equipemnt for the price of say a entry level furnace, AC/HP. If you go to the manufacturers website and look at there news statements you can find information of what may be announced for rebates and other important information a consumer might need to make a informitive decision on there furture purchase's.

[Ladiesman271]

No, it does NOT cost less.



Ok, I will play along.

Does a multistage furnace cost more to operate than a single stage furnace?

[RoBoTeq]

Ok, I will play along.

Does a multistage furnace cost more to operate than a single stage furnace?
A multistage furnace can cost more to operate then a single stage furnace. However; if properly sized, installed and operated, multistage furnaces will average the efficiency they are rated for while providing better comfort.

[beenthere]

Ok, I will play along.

Does a multistage furnace cost more to operate than a single stage furnace?
If oversized, and not installed and set up right.

Yes.

A good contractor will take the time to do a proper install. And set it up right.

And you will be more comfortable then with a single stage.

[Ladiesman271]

How does everyone define the word "comfort"?

How does everyone define a furnace as being "properly installed"? I do not consider the duct system to be part of a typical furnace replacement. If the duct work is adequate for the old system then can one assume that it would be adequate for a 90% plus replacement furnace?

As far as correct size is concerned, if you have a 90% single stage or a 90% multi stage furnace, is the correct size of each furnace based on the maximum fire rate? In other words, would both furnaces be the same size?

[DeltaT]

How does everyone define the word "comfort"?

The only way I've ever known that the customer is in their comfort zone is that they are happy, they are not calling me with complaints and that they have paid the service bills....and they continue to call me for more service when necessary or for maintenance.

Temp/ humidity, fancy or plain controls, the greatest and lastest technology and/or systems typically has nothing to do with when they feel comfort.

Now on my end - I also know that their system is installed safely and is operating safely.

[RoBoTeq]

In respect to single stage vs multistaged furnaces, comfort is a matter of how much of a temperature swing the home experiences between furnace cycles and how much difference there is between temperatures of various parts of the home.

The longer a furnace continually operates, the less temperature variation throughout the home. A staged furnace will operate longer cycles on lower fire increasing the overall operational run time.

With longer run cycles providing less heat for longer periods of time, a multistaged furnace will keep the home temperature more consistant.

[beenthere]

If a house needs a 80,000 BTU single stage for design conditions. Then a 80,000 BTU 2 stage or mod would be the right size also.

Your old furnace may not require as much air flow as a new one.

Older furnaces can operate at higher temp rises then many new ones.
An old 100,000 BTU furnace may only need 900 CFM.
Were a new 80,000 BTU may need 1200 CFM.

So, don't ASSUME your current duct system is ok for the new furnace.

Comfort is a personal perceived feeling.

Long run times from a 2 stage or mod, generally minimizes the cool draft feeling you may get right after a single stage shuts off. And can make you feel more comfortable.

[RoBoTeq]

Keep in mind two major factors;

It is the output rating that matters, and

There is a good chance your existing furnace is oversized.

So, if you have an older furnace that is rated at 80,000 Btu output that would cycle off periodically even on the coldest days, 80,000 Btu is more heat then your home requires.

If this is the case, you may want to consider downsizing the output of your next furnace.

[Ladiesman271]

If a house needs a 80,000 BTU single stage for design conditions. Then a 80,000 BTU 2 stage or mod would be the right size also.




Then the fact that you mentioned an oversized furnace in post #165 is meaningless. If a contractor oversizes a two stage it is more than likely that he oversize a single stage furnace (AKA same maximum output).







Your old furnace may not require as much air flow as a new one.

Older furnaces can operate at higher temp rises then many new ones.
An old 100,000 BTU furnace may only need 900 CFM.
Were a new 80,000 BTU may need 1200 CFM.

So, don't ASSUME your current duct system is ok for the new furnace.





Don't ASSUME that I assume anything. My home is a bit over 50 years old, and has all the original heating system as installed. Footprint is about 50' X 24' split level with basement. Ductwork has galv steel main feed and return duct sized at 24" X 8" that tapers down to 18" X 7" and then down to 14" X 7". Multiple galv steel feeds and returns in each room. They air flow capacity of the ductwork is not a concern in my case.

I have to find out how that 70* rise relates to the correct blower speed setting for the 90% + Thermo Pride units. Lower blower speeds make less noise than higher speeds. I don't have any blower information for my old furnace.

[RoBoTeq]

I'm not quite sure what you are looking for here, ladiesman.

As has been noted; oversizing furnaces, no matter if they are single of two stage, is bad, but worse for staged furnaces.

It has also been noted that lowering the blower speed increases the temperature rise. We don't have enough informative data on the ThermoPride furnace to know what exactly they are claiming with their 70° temperature rise. Hell; you want hot air out of the vents, just slow any blower down:rolleyes:.

[Ladiesman271]

Keep in mind two major factors;

It is the output rating that matters, and

There is a good chance your existing furnace is oversized.

So, if you have an older furnace that is rated at 80,000 Btu output that would cycle off periodically even on the coldest days, 80,000 Btu is more heat then your home requires.

If this is the case, you may want to consider downsizing the output of your next furnace.


I have a 50 year old 125,000 BTU input / 100,000 BTU output furnace with a single speed blower. It always cycles off, but on the coldest nights of the year it has very long run times. I have adjusted the fan / limit control for maximum efficiency and comfort.

This year I also have a direct vent fireplace that I will use at times. That unit has a 17,000 to 25,000 BTU input.

During a sunny winter day, solar gain keeps the furnace off most of the day. During the day I have a need to recirculate air with no additional heat generated by the furnace due to my split level floor plan.

I am not sure if I even need a 2 stage furnace. I am probably better off with a single stage furnace that has about a 90,000 BTU output.

[Ladiesman271]

I'm not quite sure what you are looking for here, ladiesman.

As has been noted; oversizing furnaces, no matter if they are single of two stage, is bad, but worse for staged furnaces.




Why is it worse to oversize a staged furnace as compared with a single stage furnace? From what I can tell, a properly sized staged furnace hardly ever runs in the high stage.







It has also been noted that lowering the blower speed increases the temperature rise. We don't have enough informative data on the ThermoPride furnace to know what exactly they are claiming with their 70° temperature rise. Hell; you want hot air out of the vents, just slow any blower down:rolleyes:.


Maybe a Thermo Pride heat exchanger is robust enough to work with a 70* rise as compared with other brands. From what I have read, there is a comfort factor involved that is related to blower speed (and related heat rise). There is also an air flow noise factor.

No big deal. Hot air comes out of the vents when the furnace is on in either case. Just how noisy the air flow is another matter.

[RoBoTeq]

Why is it worse to oversize a staged furnace as compared with a single stage furnace? From what I can tell, a properly sized staged furnace hardly ever runs in the high stage.
That is the problem. A furnace is prone to operate less efficiently while in low fire. Also, condensate issues that cause premature failure of furnaces occur during low fire operation. Staged furnaces need to operate in high fire occasionally, even in milder weather, in order to operate properly.

A furnace should run constantly, 24/7, when the temperatures are the lowest the furnace was designed to handle. If you anticipate zero degrees to be the very lowest your furnace should have to operate during and you want your furnace to be able to maintain 72° even when the outdoor temps are zero (no other heat factors such as solar radiation), then your furnace should be running constantly without stopping when the temperatures go to zero degrees.




Maybe a Thermo Pride heat exchanger is robust enough to work with a 70* rise as compared with other brands. From what I have read, there is a comfort factor involved that is related to blower speed (and related heat rise). There is also an air flow noise factor.

No big deal. Hot air comes out of the vents when the furnace is on in either case. Just how noisy the air flow is another matter. I don't see anything that would indicate that the ThermoPride heat exchanger is more robust then other tubular heat exchangers on the market. there is also just not a significant difference with ThermoPride's temperature rise if 70° is the high end of their temperature rise range. If that is the case, ThermoPride is using the temperature rise as a marketing gimmick and a very wrong minded one at that. Giving the consumer the impression that the higher the temperature rise, the better the furnace, is a very dangerous thing. The last thing that consumers should be doing is seeking higher temperature rises.

As I have explained before; the higher the temperature rise, the lower the efficiency.

[RoBoTeq]

I have adjusted the fan / limit control for maximum efficiency and comfort.


Really? Just how do you do this? Since no matter what you set an adjustable fan/limit control to you always sacrifice efficiency for comfort and visa versa, just how do you set one for both maximum efficiency "and" comfort?

Your new furnace will not have an adjustable fan/limit control. You may want to factor that into buying a new one that you won't be able to play with:rolleyes:.

[Ladiesman271]

Really? Just how do you do this? Since no matter what you set an adjustable fan/limit control to you always sacrifice efficiency for comfort and visa versa, just how do you set one for both maximum efficiency "and" comfort?

Your new furnace will not have an adjustable fan/limit control. You may want to factor that into buying a new one that you won't be able to play with:rolleyes:.


You really should do some research.

I recently read an old study compiled in 1951 from data taken from 1941 through 1943. This study was based on real world measurements taken from an actual house built for the National Warm Air Heating and Air Conditioning Association for this purpose. The AGA provided funds and technical assistance for this study and compilation of data. The mechanical engineering department of a university did the study.

Anyhow, the study mentioned three methods of burner control that can be used to balance heat loss of the building with heat gain from the heating system under different weather conditions.

1. Modulating burner

2. 2 Stage burner (considered a subset of modulating burner)

3. Intermittent operation of a burner with a fixed fuel input rate.

I happen to use method number three. My furnace has an adjustable burner control and limit switch. The upper limit has a maximum set point that you can not exceed. I set the upper limit of the adjustable to make sure that the furnace does not overheat the plenum. The lower limit is set for a 20* differential to turn back on when the fan cools down the plenum.


How you set the fan control on / off temperatures determines how much of the heat generated is used in an efficient manner. The length of time that the blower runs depends on the weather and how you setup the burner and fan switches.


I have been doing this for over 20 years, but I just ran across this old study a few months ago. At the time of the compilation (1951), a 70* to 100* heat rise was required for an approved furnace. That did not mean that you had to setup the furnace to obtain a 70* heat rise. As a matter of fact, different setups provided heat rises of 35* to 70* depending on which burners, blower speeds and control settings were used for evaluation purposed.

[RoBoTeq]

You really should do some research.

I recently read an old study compiled in 1951 from data taken from 1941 through 1943. This study was based on real world measurements taken from an actual house built for the National Warm Air Heating and Air Conditioning Association for this purpose. The AGA provided funds and technical assistance for this study and compilation of data. The mechanical engineering department of a university did the study.

Anyhow, the study mentioned three methods of burner control that can be used to balance heat loss of the building with heat gain from the heating system under different weather conditions.

1. Modulating burner

2. 2 Stage burner (considered a subset of modulating burner)

3. Intermittent operation of a burner with a fixed fuel input rate.

I happen to use method number three. My furnace has an adjustable burner control and limit switch. The upper limit has a maximum set point that you can not exceed. I set the upper limit of the adjustable to make sure that the furnace does not overheat the plenum. The lower limit is set for a 20* differential to turn back on when the fan cools down the plenum.


How you set the fan control on / off temperatures determines how much of the heat generated is used in an efficient manner. The length of time that the blower runs depends on the weather and how you setup the burner and fan switches.


I have been doing this for over 20 years, but I just ran across this old study a few months ago. At the time of the compilation (1951), a 70* to 100* heat rise was required for an approved furnace. That did not mean that you had to setup the furnace to obtain a 70* heat rise. As a matter of fact, different setups provided heat rises of 35* to 70* depending on which burners, blower speeds and control settings were used for evaluation purposed.
:DWell, that study is older then I am, so I guess I'd best conceede you are on top of things more then me:rolleyes:.

As long as nothing has changed in the way furnaces are being made today from over half a century ago, I certainly cannot argue with your findings.

[larobj63]

You really should do some research.

I recently read an old study compiled in 1951 from data taken from 1941 through 1943. This study was based on real world measurements taken from an actual house built for the National Warm Air Heating and Air Conditioning Association for this purpose. The AGA provided funds and technical assistance for this study and compilation of data. The mechanical engineering department of a university did the study.



Come on man, are you serious? :o

"Intermittent operation of a burner with a fixed fuel input rate" = Cycling

[Ladiesman271]

Come on man, are you serious? :o

"Intermittent operation of a burner with a fixed fuel input rate" = Cycling



Come on man, are you serious????????????????????????????????????? :o

Maybe a HVAC tech can understand the concept, but maybe not. This may be way over your heads because it is just so technical!:rolleyes:

http://www.freepatentsonline.com/4470267.html

[Ladiesman271]

:DWell, that study is older then I am, so I guess I'd best conceede you are on top of things more then me:rolleyes:.

As long as nothing has changed in the way furnaces are being made today from over half a century ago, I certainly cannot argue with your findings.


The study was not about furnaces. The study was about comfort and the amount of fuel (gas and electric) to obtain this comfort.

They defined what the word comfort means. The measured the temperatures at three specific levels in each and every room in the home for two years. They evaluated different furnace setups using the same identical furnace. They compared a single stage setup with two different control settings, a single stage setup with an automatic dual speed blower, and a dual stage burner setup with a single and two speed blower.

They did determine the most efficient and comfortable furnace setups by testing rather than the methods used on this board!:p

[DeltaT]

Everybody may be a little more right on this subject according to their history of experience in this field then they know.

When that report was done technology was switching from an open burner natural hot air supply (otherwise know as a gravity or ocotopus furnace) to an open burner, forced air cabinet or some form. Many of the converted or "newer" furnaces with forced air fans had a difficult time regulating the temp of the air supplied to the home. And many home owners, who were use to the natural hot draft out of their big wall supplies, complained.

So the combination upper limit & fan control was invented. On many of the old furnaces they were two seperate devices but Honeywell first invented, I think, the first high limit/fan control combination still sold today.

And many of the limit and/or fan control devices were actually added in one of the "trunk" runs and not located on the furnace itself. It varried. And most of the trunk runs were not sized but pretty equally common since most of the time the furnace was purposely located as close to the center of the basement as possible so all the hot air would equally reach all trunk runs.

The fan control was sometimes use as the supply temp regulator along with the high limit, depending on the individual techs mind set and/or the owners complaint level.

We all still run into octopus furnaces that have the added on fans assemblies for forced air conversions. There are still some out there running to this day.

There were some techs, such as myself, that added two speed blower motors on these types of systems either connected to speed up or slow down depending on the result I wanted. Sometimes the home owner asked us to add a toggle switch on the side so they could run their fans at the different speeds base on their desire.

And we all have run into older furnaces with the "summer" fan switch where the home owners, before central air was affordable, would run the furnace fan to create circulation on the main floor. Later RA manual dampers could be added at the basement RA duct to circulate the basement cool air to upstairs. All of us have seen our share of those.

Applying 50's technical info to equipment built since the modernization and introduction of the higher efficiency furnace also built and designed to be capable of heating and moving enough air for cooling just doesn't work. These are two different worlds.

You would have had to be in this field long enough to see and experience this transformation though to understand it fully.

[larobj63]

Come on man, are you serious????????????????????????????????????? :o

Maybe a HVAC tech can understand the concept, but maybe not. This may be way over your heads because it is just so technical!:rolleyes:

http://www.freepatentsonline.com/4470267.html

Can you honestly say that no advances in comfort technology have superseded the findings of the study you read?

I browsed the patent you posted a link to. Many of the claims are simply not true, at least not any more (that patent was filed in 1983?).

Short cycling a burner and especially a compressor (related to the refrigerant cycle) has long been proven to have adverse effects on efficiency. Quite a contradiction to the theory behind a plenum stat cycling the burner / compressor in the name of efficiency.

I must admit I did not read the whole patent, what I did read was not leading me to believe I could learn anything from it.

Besides, me thinks you are trolling for an argument.

Why join a community of people actually in this profession and start off by telling people they should "do some research", and that your info is over our heads. There is a wide range of knowledge and education in here. If you think you're so far ahead of the curve that we can't keep up with your 50 year old theories on efficiency and comfort, - it makes you the dumbest guy in the room, not the smartest. ;)

[Ladiesman271]

Applying 50's technical info to equipment built since the modernization and introduction of the higher efficiency furnace also built and designed to be capable of heating and moving enough air for cooling just doesn't work. These are two different worlds.

You would have had to be in this field long enough to see and experience this transformation though to understand it fully.




The worlds are not that different if you look at the basics. Keep this limited to heating.

How efficient a furnace generates heat has changed over the years. Obviously, the basics of no standing pilot, condensing furnaces and piping combustion air in from outside the building boosts furnace efficiency. That is hardly the point. The thermodynamics of heat loss of the building, duct efficiency and the heat required to compensate for indoor / outdoor temperature differential is still the same today as it was in the 40's.


Do new and old furnaces have high limit switches?

Yes. Same use yesterday and today.


Does new and old equipment control the blower?

Yes. Old blowers were controlled by temperature (some by time), and new equipment is controlled by time. For all practical purposes the controls serve the same purpose. Variable temperature, or variable time. Blower time delay is a zero cost item in a modern controller.


Does new and old equipment have a specified blower speed for heat?

Yes. As a matter of fact, the old furnace from the 1940's data uses the same blower speed as a modern 90+ % Thermo Pride (same BTU output).

http://www.thermopride.com/manuals/mg-1006.pdf



Now back to the original question. Which furnace setup uses less energy (gas and electric) to generate and deliver heat? A multi-stage furnace or a single stage furnace? Any study to back up your position?


One futher note. It would surprise you on how many posters on this thread have made claims that match up with what was known prior to 1951!

[Ladiesman271]

Can you honestly say that no advances in comfort technology have superseded the findings of the study you read?

I browsed the patent you posted a link to. Many of the claims are simply not true, at least not any more (that patent was filed in 1983?).

Short cycling a burner and especially a compressor (related to the refrigerant cycle) has long been proven to have adverse effects on efficiency. Quite a contradiction to the theory behind a plenum stat cycling the burner / compressor in the name of efficiency.

I must admit I did not read the whole patent, what I did read was not leading me to believe I could learn anything from it.

Besides, me thinks you are trolling for an argument.

Why join a community of people actually in this profession and start off by telling people they should "do some research", and that your info is over our heads. There is a wide range of knowledge and education in here. If you think you're so far ahead of the curve that we can't keep up with your 50 year old theories on efficiency and comfort, - it makes you the dumbest guy in the room, not the smartest. ;)


Yup, this thread is about heating and you are talking AC. You do not read, and then you look for an argument.

[RoBoTeq]

Sorry ladies, but you have a lot of wrong minded thinking going on.

No; limits of today are nowhere near the same as limits of yesteryear other then the fact that they are limiting a function.

Since you have no respect for those of us in the industry, I have no desire to converse with you any further. All you seem to want to do is to criticize the pros on this site with outdated data and wrongminded thinking you believe to be logic.

I'm not sure what your needs are, but it is annoying to have so much wrong information being communicated by someone who wrongly thinks they are superior to those in the HVAC industry.

[RoBoTeq]

The worlds are not that different if you look at the basics. Keep this limited to heating.

How efficient a furnace generates heat has changed over the years. Obviously, the basics of no standing pilot, condensing furnaces and piping combustion air in from outside the building boosts furnace efficiency. That is hardly the point. The thermodynamics of heat loss of the building, duct efficiency and the heat required to compensate for indoor / outdoor temperature differential is still the same today as it was in the 40's.


Do new and old furnaces have high limit switches?

Yes. Same use yesterday and today.


Does new and old equipment control the blower?

Yes. Old blowers were controlled by temperature (some by time), and new equipment is controlled by time. For all practical purposes the controls serve the same purpose. Variable temperature, or variable time. Blower time delay is a zero cost item in a modern controller.


Does new and old equipment have a specified blower speed for heat?

Yes. As a matter of fact, the old furnace from the 1940's data uses the same blower speed as a modern 90+ % Thermo Pride (same BTU output).

http://www.thermopride.com/manuals/mg-1006.pdf



Now back to the original question. Which furnace setup uses less energy (gas and electric) to generate and deliver heat? A multi-stage furnace or a single stage furnace? Any study to back up your position?


One futher note. It would surprise you on how many posters on this thread have made claims that match up with what was known prior to 1951!
OH geez....you're a ThermoPride salesman!

[larobj63]

Yup, this thread is about heating and you are talking AC. You do not read, and then you look for an argument.

Huh? I'm looking for an argument?

I'm with roboteq on this. See ya.

[DeltaT]

The worlds are not that different if you look at the basics. Keep this limited to heating.

How efficient a furnace generates heat has changed over the years. Obviously, the basics of no standing pilot, condensing furnaces and piping combustion air in from outside the building boosts furnace efficiency. That is hardly the point. The thermodynamics of heat loss of the building, duct efficiency and the heat required to compensate for indoor / outdoor temperature differential is still the same today as it was in the 40's.


Do new and old furnaces have high limit switches?

Yes. Same use yesterday and today.


Does new and old equipment control the blower?

Yes. Old blowers were controlled by temperature (some by time), and new equipment is controlled by time. For all practical purposes the controls serve the same purpose. Variable temperature, or variable time. Blower time delay is a zero cost item in a modern controller.


Does new and old equipment have a specified blower speed for heat?

Yes. As a matter of fact, the old furnace from the 1940's data uses the same blower speed as a modern 90+ % Thermo Pride (same BTU output).

http://www.thermopride.com/manuals/mg-1006.pdf



Now back to the original question. Which furnace setup uses less energy (gas and electric) to generate and deliver heat? A multi-stage furnace or a single stage furnace? Any study to back up your position?


One futher note. It would surprise you on how many posters on this thread have made claims that match up with what was known prior to 1951!

With all due respect because I am sure you mean well, but I will also discontinue attempting to discuss this with you as I can not follow your trail of logic.

You seem to present specific information to support your point of view, but when challenged you present such general leaps of logic such as - "The worlds are not that different if you look at the basics" -that equating the laws of physics in general does not bring this dicsussion back to specifics.

It's almost like a circular argument.

Anyway, thanks but that's enough from me.

[praha99]

Ladiesman youll have to give it up..HOBOteq is never wrong .. just ask him.
:D

[RoBoTeq]

Ladiesman youll have to give it up..HOBOteq is never wrong .. just ask him.
:D
And yet another useless post. Ahhh, the price of having groupies:rolleyes:

[beenthere]

Then the fact that you mentioned an oversized furnace in post #165 is meaningless. If a contractor oversizes a two stage it is more than likely that he oversize a single stage furnace (AKA same maximum output).

Actually, some contrators seem to want to intentionally over size 2 stage. And will justify over sizing it because it is 2 stage.







Don't ASSUME that I assume anything. My home is a bit over 50 years old, and has all the original heating system as installed. Footprint is about 50' X 24' split level with basement. Ductwork has galv steel main feed and return duct sized at 24" X 8" that tapers down to 18" X 7" and then down to 14" X 7". Multiple galv steel feeds and returns in each room. They air flow capacity of the ductwork is not a concern in my case.

I have to find out how that 70* rise relates to the correct blower speed setting for the 90% + Thermo Pride units. Lower blower speeds make less noise than higher speeds. I don't have any blower information for my old furnace.


From your post, #167:

How does everyone define a furnace as being "properly installed"? I do not consider the duct system to be part of a typical furnace replacement. If the duct work is adequate for the old system then can one assume that it would be adequate for a 90% plus replacement furnace?

You asked if you can assume.

I answered.

You assumed.

[beenthere]

I recently read an old study compiled in 1951 from data taken from 1941 through 1943. This study was based on real world measurements taken from an actual house built for the National Warm Air Heating and Air Conditioning Association for this purpose.

That study was also done during the time period when supplies were installed on the inside walls, and returns were on the outside walls.

So any method used to extend furnace run time, would improve comfort.

[House]

Now back to the original question. Which furnace setup uses less energy (gas and electric) to generate and deliver heat? A multi-stage furnace or a single stage furnace? Any study to back up your position?



Furnace only study: http://ees.ead.lbl.gov/bibliography/residential_two_stage_gas

Ductwork considerations: http://www.osti.gov/bridge/product.biblio.jsp?query_id=2&page=1&osti_id=812518

Both must be read to get a full understanding.

[Ladiesman271]

That study was also done during the time period when supplies were installed on the inside walls, and returns were on the outside walls.

So any method used to extend furnace run time, would improve comfort.



Per the study:

"The trends indicated by the investigation reported in this bulletin show the validity of the "continuous air circulation" principle."

[beenthere]

You haven't lived in a home with the supplies on the inside walls, and the returns on the outside walls.

Continuous air circulation does improve comfort with either set up.

But with the older register grille placement. To be comfortable it was almost a requirement(or you had to set the temp up high). As the outside walls always remained cold. And would make anyone feel cold that was sitting close to them(increases the bodies radiant heat loss).

That set up always left a wide temp difference between the outside and inside walls.

You can have any type furnace installed that you want.
Part of customer comfort. Is the customer being happy with their choice.

[Ladiesman271]

Furnace only study: http://ees.ead.lbl.gov/bibliography/residential_two_stage_gas

Ductwork considerations: http://www.osti.gov/bridge/product.biblio.jsp?query_id=2&page=1&osti_id=812518

Both must be read to get a full understanding.



The first link answers the question very well. Two stage furnaces do not save energy as compared with the same single stage model.

The second link about ductwork applies to ducts in unconditioned areas. That information applies to some systems, and not to others. In my specific case the ductwork is all in the conditioned area, so any energy loss would be "lost" into the conditioned area (AKA no loss).

[RoBoTeq]

That study was also done during the time period when supplies were installed on the inside walls, and returns were on the outside walls.

So any method used to extend furnace run time, would improve comfort.
However, contrary to ladies logic, raising the temperature differentual decreases run time. There are also issues with the heat retention of furnaces from this time period that are no longer factored in with cycle rates and temperature swings.

[Ladiesman271]

You haven't lived in a home with the supplies on the inside walls, and the returns on the outside walls.

Continuous air circulation does improve comfort with either set up.

But with the older register grille placement. To be comfortable it was almost a requirement(or you had to set the temp up high). As the outside walls always remained cold. And would make anyone feel cold that was sitting close to them(increases the bodies radiant heat loss).

That set up always left a wide temp difference between the outside and inside walls.

You can have any type furnace installed that you want.
Part of customer comfort. Is the customer being happy with their choice.


Yes, the duct layout in that old study is as you described. They showed floor layout, duct sizes, duct length, outlet location. For purposes of the comfort evaluation, they excluded temperature differences in the horizontal plane in any particular room. The study also ignored temperature of surfaces.

The discussion on this thread as well at that old study are not evaluating different methods of distribution of conditioned air though a duct system. Whether any particular furnace works properly with an existing duct system is a different subject. Whether an existing duct system was even designed and installed properly in the first place is also another subject.

That being said, I realize that the proper ductwork is critical for a "quality" install. However, posters (meaning not you personally) should be clear on what part of the install they are talking about and not jump back and forth between the furnace selection and the duct system.


Anyhow, the conclusion of that old study was that a properly setup single stage furnace single speed fan and a properly setup 2 stage burner single speed fan furnace had similar comfort and operational costs (electric and gas use) with a temp difference of 55*. With a temperature difference of 35*, the 2 stage furnace used more fuel (4% increase).


So, has anything really changed over the years (meaning does a 2 stage furnace cost more to operate than a single stage furnace of the same design)?

[Ladiesman271]

However, contrary to ladies logic, raising the temperature differentual decreases run time. There are also issues with the heat retention of furnaces from this time period that are no longer factored in with cycle rates and temperature swings.


My present furnace is a 1957 install. I adjust the blower temp setting to lower the temperature differential, not to raise it. That old study showed a 15% difference in fuel use with that one adjustment.

Yes, a thick wall heat exchanger takes a while to heat up and to cool down. Even though my furnace has a temperature controlled blower sensor, a time feature would work just as well. About 5 minutes to blower turn on after buner starts, and 5 minutes to cool down after burner stops.

Modern furnaces have adjustable on / off times for the blower somewhere up to two minutes. The new heat exchanges are thinner and a different design, so time is set so you don't burn them out.

Anyhow, how I adjust my old furnace is hardly the issue. I wish I knew what the CFM my old furnace blower is so I can make a duct flow rate comparison (AKA FPM air flow noise level evaluation) with a potential new furnace. The 70k and 90K BTU output furnaces use two different blower speeds.

[homersodyssey]

http://www.achrnews.com/CDA/Articles/Breaking_News/BNP_GUID_9-5-2006_A_10000000000000475213

It seems ASHRAE likes the York mod.