A few questions for those in the know

[uncleblaine]

My 2-story home in central Minnesota currently has a Ruud HR-125JD gas furnace. Does anyone have any idea what kind of efficiency this model has? I've owned the home for 9 years, but I've no idea when the furnace was put in, though I doubt it is an original 1958 model.

It's rating is 125000 BTU/hr with 100000 BTU bonnet capacity. Can I use that as a wild guestimate for proper sizing of a new unit? Also, I intend on replacing the current junk US Steel windows as part of the entire project. Is it safe to assume my BTU needs should be less with energy star windows? I've got calls to set up estimates with the local Bryant, Trane, and Rheem dealers but haven't heard back yet. Given the approaching cold and rising NG prices, if they get back in the next few days I'll be pleased. I'm thinking I want to go 90+ efficiency on the furnace and replace my 3 ton(?) AC unit at the same time. I have a Trion electronic air cleaner and a Skuttle humidifier that I would like to be able to keep using as they are under 3 years old. Is this realistic or a pipe dream?

Anything you could assist with would be greatly appreciated. This forum is a great resource!

[anonymous]

fill in some information about you in your profile. We don't like diy's trolls here. you will have to call a professional.

[uncleblaine]

Sorry. A *troll* I am not, and resent the implication, actually. While I like to consider myself a DIYer, I know better than to tackle a project like this, or the windows for that matter. But I do like to go into a project with *some* knowledge, which is why I'm here. I'll answer any question you'd like to ask me, and I'll go put some info in my profile as well.

[dash]

1000,000 divided by 125,000 is 80% ,that's your current efficiency.

Changing windows will likely lower the size needed,maybe for cooling as well.If insulation can be added ,it's a good time for that as it helps lower the size needed as well.

A manual J load calc, or based on manual J, is needed to size the heating and the cooling.

The red tab above will allow you to do your own calculation for a small fee.

See http://www.acca.org as well,for info. only.

Tell all contractors that you insist on this before setting any appointment.


Keeping the air cleaner and humidifier should be no problem,some here will knock the Electronic ,but if you clean it often ,they work just fine.

Ask the Bryant guy about the Evolution furnace and Controler.

[dash]

Originally posted by uncleblaine
Sorry. A *troll* I am not, and resent the implication, actually. While I like to consider myself a DIYer, I know better than to tackle a project like this, or the windows for that matter. But I do like to go into a project with *some* knowledge, which is why I'm here. I'll answer any question you'd like to ask me, and I'll go put some info in my profile as well.

Just ignore his post,some just want to start a fued.

[ct2]

Although you have a furnace in your home now , there are to many variables to answer the questions you have asked . Given the fact that you are installing new windows you really should have a load calculation done and any /all of the contractors that give you an estimate should do a manual j to determine what your needs really are

http://hphaa.com/services/installation/installation.htm

go to this website and read read read....

you will find many answers there

[uncleblaine]

Hey thanks dash! I checked out that j-calc thing last night but didn't download it as I wasn't sure if it was worthwhile when I'm not entirely sure of the insulation, for example, in the house. If nothing else, for fifty bucks it would be interesting to compare the numbers with different window materials. These steel things are so worthless I could just as well leave them open in the winter, or buy stock in 3M window coverings.

I'm at work now (yep a very slow day,) but I'm going to do the calculator tonight.

The Bryant Evolution is actually the first unit I glommed onto, so I'm glad to hear it recommended.

Thanks again!
Blaine

[uncleblaine]

dash and ct2,

If I do this load calc thing from the tab above, am I best to keep that information to myself and ask the contractors to do one? Or should I share it and perhaps let them make adjustments as needed. When they do a load calculation is it done in a similar manner as this program does it, or do they have measuring equipment or somesuch that does a more accurate job?

Thanks again guys!

[Irascible]

Originally posted by dash
some here will knock the Electronic ,but if you clean it often ,they work just fine. I couldn't have said it better myself. I do indeed knock electronics because so few customers are willing to put in the work necessary. :^)

[Irascible]

Originally posted by uncleblaine
The Bryant Evolution is actually the first unit I glommed onto, so I'm glad to hear it recommended.You don't know Dash. He'd recommend pet porcupines if Carrier branded them. ;)

But seriously- It's a very good product IF you have an exceptionally well trained contractor and the right application. The zoning and humidity control aspects of the system are excellent. But if you're not installing zoning and if controlling humidity isn't a major issue (I don't know your climate.) then it's not worth the expense and complexity in my opinion.

Let the contractors do their own calcs and then compare the results. Don't be surprised if the results vary tremendously from your own. Fearful contractors are wont to throw in fudge factors.

[Jultzya]

Do the load calc so you will have an idea as to the sizing.

Keep it to yourself at first. Try choosing the best contractor you can possibly find.

If the load calc is way off, ask why. But let them tell you their size of equipment first! That way you will have an idea if they are GUESSING! They need to measure windows, doors, ceiling height, insulation, etc..

One last comment, the best equipment install wrong is going to be the biggest POS you ever owned. So get the BEST installer you can find and have them install the equipment brand that he recommends.

[dash]

You can make mistakes doing your own calculation,but so can the contractor.

I keep it to myself ,until after they size it,and ask them to show you why theirs is different,if they don't match.

I'd do it and run different windows that you might buy as well as different R values for areas that insulation can easily be added.this can help dtermone what to add to best reduce the load to maybe a 90,000 but furnace and a 2.5 ton system.Reducing the system size saves operating cost and If your duct system is too small ,can make it the correct size.


Now ,Infinity/Evolution,check out "All" the features,and it may be what "You" want.

It really is easier than most to install,wiring ,configuration ,no dip switches to set,etc.,etc..I say the systems that come close it in features ,require more training ,than Infinity/Evolution,including the Carrier/Bryant Thermidistat.IMHO.

[Christheheatingdude]

Originally posted by anonymous
fill in some information about you in your profile. We don't like diy's trolls here. you will have to call a professional.

Is this who I think it is?


Anyway on to the topic.

Uncleblaine, can't really add anymore than dash told you. Follow his recomendations and you should be golden.

Happy Heating

[uncleblaine]

Originally posted by Christheheatingdude

Originally posted by anonymous
fill in some information about you in your profile. We don't like diy's trolls here. you will have to call a professional.

Is this who I think it is?




Well my weblogs say the first visitor after putting my url in the profile was from Florida, if that helps. But several more have visted from Georgia, California and Connecticut. I'll refrain from offering anything more specific. :) Statcounter is a wonderful thing for those of you who have websites... and it's free.

Anyway, I appreciate all the input you guys have offered. I'll be spending some time reading up on those sites, and will download the calculator tonight. My wife recently did an excercise appraisal on our house so I'll have many of the measurements handy.

Of the folks I've called, the Bryant contractor and the Carrier/Trane (yep, that's what they carry) contractors both have sterling and long reputations in the area. The Rheem guy is less well known, but will try to check things out further if he seems a likely candidate.

I'll keep you posted and if I can get through the calculator tonight I'll post my results.

Thanks again!
Blaine

[mlbussert]

Sorry, I can't help you as I am a HO myself in the process of buyin a new AC/Furnace, and I have found the people in this site very helpful and knowledgeable so that I can make a decision as to which contractor to go with.

However, I have to comment that I could not stop laughing since I find it highly ironic that someone with the username "anonymous" would ask you fill out your profile.

[uncleblaine]

Ain't that the truth!

If you're still looking for info, check out the hphaa.com link ct2 posted. Incredible information!

I many times will highlight a line of text to use as a page mark when I'm called away from the computer. Was taken aback when it wouldn't work. Then I thought about it a bit more. VERY smart call!



[Edited by uncleblaine on 10-08-2005 at 06:18 PM]

[uncleblaine]

Okay, I've done the manual J, and here's the whole house results if anyone is interested.

With current windows:
S/Gain L/Gain T/Gain T/Loss
15596 3417 19013 53612

With new windows, patio door and front door:
14659 3417 18076 47427

That's just shy of 6200 BTU less heat loss. To me that seems quite substantial, but I'm a laymen. And in all actuality, the only changes made in the program were to lowE glass, and vinyl frame. The old windows leak like seives so the real difference may be greater.

Back to studying recommended links...

[Irascible]

Originally posted by uncleblaine
I many times will highlight a line of text to use as a page mark when I'm called away from the computer. Was taken aback when it wouldn't work. Then I thought about it a bit more. VERY smart call!Well... not really. I was trying to protect my content. But you have no idea how easy it is to circumvent the no highlight/no right click feature. I'll let you figure it out on your own. ;^)

[uncleblaine]

Originally posted by Irascible Well... not really. I was trying to protect my content. But you have no idea how easy it is to circumvent the no highlight/no right click feature. I'll let you figure it out on your own. ;^)

LOL Actually, I do, but at least it keeps most honest people honest. I've been through that a bit myself. I'm just happy to read the info, I don't want to "borrow" it. :D

I imagine there's at least a few less than upstanding contractors who aren't pleased with your truth-speaking. Kudos to you for doing it. Excellent information!

[dash]

Originally posted by uncleblaine
Okay, I've done the manual J, and here's the whole house results if anyone is interested.

With current windows:
S/Gain L/Gain T/Gain T/Loss
15596 3417 19013 53612

With new windows, patio door and front door:
14659 3417 18076 47427

That's just shy of 6200 BTU less heat loss. To me that seems quite substantial, but I'm a laymen. And in all actuality, the only changes made in the program were to lowE glass, and vinyl frame. The old windows leak like seives so the real difference may be greater.

Back to studying recommended links...

Imporovements saving 5% on cooling,and 11% on heating.

That's like buying a half of SEER more ,and going from an 80 to a 90 % furnace.

[uncleblaine]

Originally posted by dash
Imporovements saving 5% on cooling,and 11% on heating.[

That's like buying a half of SEER more ,and going from an 80 to a 90 % furnace.

Well hopefully doing the a 90+ furnace and several SEER on the AC can save that much again. Perhaps I need to hope for cold winters and hot summers so I can have a quicker payoff. :D

[dash]

Originally posted by uncleblaine

Originally posted by dash
Imporovements saving 5% on cooling,and 11% on heating.[

That's like buying a half of SEER more ,and going from an 80 to a 90 % furnace.

Well hopefully doing the a 90+ furnace and several SEER on the AC can save that much again. Perhaps I need to hope for cold winters and hot summers so I can have a quicker payoff. :D

Don't forget the higher utility costs more likely than the weather changing that much.

[dan sw fl]

Originally posted by uncleblaine
Okay, I've done the manual J, and here's the whole house results if anyone is interested.

With current windows:
S/Gain L/Gain T/Gain T/Loss
15,596 3,417 19,013 53,612

With new windows, patio door and front door:
14,659 3417 18,076 47,427

That's just shy of 6200 BTU less heat loss. To me that seems quite substantial, but I'm a laymen. And in all actuality, the only changes made in the program were to lowE glass, and vinyl frame. The old windows leak like seives so the real difference may be greater.

Back to studying recommended links...

Blaine,

Why would you have existing 100,000 BTUh capacity and
53,612 BTUh need per your analysis ?

I believe your have performed analysis which does
not show Total BTU loss.
Infiltration is a huge contributor to this difference.

Say house is 30 x 50 x 20 foot tall = 30,000 Cubic feet
Using a "Quite LOOSE" value 0.6 ACH yields
~ 300 CFM infiltration.
Q= CFM * dt * 1.08
1.08 = constant

Q= 300 CFM * 81 'F dT * 1.08 = 26,400 BTUh
Estimated Current Load
26,400 + 53,600 = 80,000. BTUh MAX ( 81 'F dT)
Of course, review of heating energy bill would be quite useful at this point.

You could obtain infiltration of 0.25 ACH or 125 CFM with
new windows and significant caulking / spray foam effort.

Q net savings = 175 * 81 * 1.08 = 15,309 BTUh
at design temp of -11'F
----------

WINDOWS
Q= U * A * Dt
U= 1.0 for Old perhaps
U= 0.3 for New ? ONLY As an example

A (Total window area) might be 200 Sq.Ft per floor
Dt = -11'F + 80 = 81'F

Qnew windows = 0.3 x 200 x 81 = _4,860
Qold windows = 1.0 x 200 x 81 = 16,200

Energy Savings per 200 Sq. Ft.= 11,340 BTUh
---------------

I would expect > 20,000 BTUh total savings given this
set of ASSUMED values ( adjust as appropriate)
which may "get you in the ballpark"
of a Energy Saving$ goal.

Perhaps, purchase of a ~70,000 BTUh 90% efficient furnace
(63,000 BTUh NET)
is what you may be able to pursue with integrated improvements in housing Envelope AND Heating equipment.

[uncleblaine]

Hi Dan,

Why would you have existing 100,000 BTUh capacity and
53,612 BTUh need per your analysis ?

I don't know. I questioned it too, but just used the software. Of course it was my first time. Infiltration is listed at 15956 BTUH total loss. Perhaps I should run through my entries to see if I've made a major gaffe. I'll also try plugging my measurements into your calcs to see what I arrive at.

edit to add

Infiltration numbers are shown as .4 summer and .7 winter, on 2752 square feet. This is using average/loose construction figures built into the software.



[Edited by uncleblaine on 10-09-2005 at 11:53 AM]

[Freezeking2000]

I am wondering if during the coldest windy nights did your existing furnace EVER run for 30+ minutes?

I know that when -20F with 30 MPH winds the heating equipment get a good run. You do not want to be short capacity in Minn. when temps drop below design temp. I would get a 2 stage system so the heat will run constantly and go to high fire when exreme temps hit.

Also I hear the 90+ units are not as reliable, but I hat be incorrect since I am a Refrigeration man. I do know you cant go without heat for more than a few hours in Minn.

Ask the contractors what they recommend for the severe winters you have! They are the ones that have to make it work on the cold winter night when it is -20.

[uncleblaine]

Originally posted by Freezeking2000
I am wondering if during the coldest windy nights did your existing furnace EVER run for 30+ minutes?

I know that when -20F with 30 MPH winds the heating equipment get a good run. You do not want to be short capacity in Minn. when temps drop below design temp. I would get a 2 stage system so the heat will run constantly and go to high fire when exreme temps hit.

Also I hear the 90+ units are not as reliable, but I hat be incorrect since I am a Refrigeration man. I do know you cant go without heat for more than a few hours in Minn.

Ask the contractors what they recommend for the severe winters you have! They are the ones that have to make it work on the cold winter night when it is -20.

You know the more I think about it, the more I'm wondering if the units are oversized, and perhaps the ducting undersized. To be honest I've never really paid attention to how long the furnace runs in any given cycle, but I'm going to start now. And oversized or not, the two-stage has been in the front of my mind for a more even temp and its comfort, if no other reason. That would also make my air cleaner do its job better. Though 2 of 5 animals have passed on since that was put in, so it already has less work to do.

[uncleblaine]

Dan,
I'm getting lost in your calculations, but I have 21392 cubic feet in the house. I attempted to get my gas usage numbers from the online bill pay, but what I can access right now does not include Oct04-Feb05, which are going to be the ones that really count. I should be able to get them tomorrow during business hours and will post gas usage then.

I'm not sure if I'm ridiculously off on my load calc, or if the equipment is ridiculously off. It wouldn't be the first thing about the house that was half-a**ed.

[dash]

Unit oversized ducting undersized,that's normally the case.Sad but true.

[uncleblaine]

Gas usage in therms for the last year total 866. Based on the gas usage for no-heat months, I'd estimate about 20 therms are used for hot water each month. That leaves me 626 therms used on heat with my current 80 efficiency furnace.
626 Therms = 62,600,000 BTU

[edited to reflect correct efficiency numbers]

62,600,000 *.63 = 39,238,000 BTU into the house

To get 39,238,000 BTU with a 92 AFUE divide by .92 right?

That's 42,867,391 BTU

divided by 100,000 = 429 Therms. Or a savings of about 197 therms.

I definitely like these numbers better.

[Edited by uncleblaine on 10-20-2005 at 09:40 AM]

[tbox8098]

Blaine,

I am currently working on finalizing your proposal, I will have it finished up tomorrow. I should be able to help with some of the additional questions when we get a chance to talk in a couple days.

Talk to you soon,

Travis

[uncleblaine]

Originally posted by tbox8098
Blaine,

I am currently working on finalizing your proposal, I will have it finished up tomorrow. I should be able to help with some of the additional questions when we get a chance to talk in a couple days.

Talk to you soon,

Travis

Hey, I was wondering what happened to you! ;) Even at a couple of days from now, you'll probably still be the first bid in hand.

Don't forget to add on for that placebo stat from the other thread. :D

[tbox8098]

It takes a while to get the options put together. I will give you a call tomorrow.

Travis

[uncleblaine]

Sounds good Travis. Use the cell number as before.

Thanks!

[tbox8098]

Blaine,

For your knowledge the furnace was only produced between 1972 and 1975 according the Preston's guide to furnaces, it also gives an estimated efficiency between 60.2 and 62.9% AFUE. The air conditioner wasproduced between 191987 and 1991 with a SEER rating between 9.2 and 9.4.

I hope this helps

Talk to you later,

Travis

[uncleblaine]

Travis,
Thanks for that info! That makes me feel much better that I'm doing the right thing.

[kjones]

Hey Travis, as long as you have that guide book dusted off, could you see what it says about a Premier GA150?

Thanks,

KJ

[troyorr]

Go back to your fourth grade math class. 125,000 in and 100,00 out. Sounds like 80%.

[Noel Murdough]

You don't know Dash. He'd recommend pet porcupines if Carrier branded them. ;)


I'll have to check the brand on this one.

Living in the boondocks, you have a lot of time on your hands......

Noel

http://www.imagewiz.net/usr/hvac1/24352_porky02sss__2_.jpg

http://www.imagewiz.net/usr/hvac1/24353_porky10s.JPG

http://www.imagewiz.net/usr/hvac1/24355_porky05.jpg

[tbox8098]

And old furnaces never lose efficiency. Or do they?

[uncleblaine]

Originally posted by troyorr
Go back to your fourth grade math class. 125,000 in and 100,00 out. Sounds like 80%.

Well gee, I'm not sure if this is meant for me or not. Prior to the post saying I could divide the numbers, they meant nothing to me, a homeowner. Then I had that post saying 80, which I went by. Until, that is, my local professional who is *bidding* on the job and actually looked at the furnace posted on this forum that its estimated efficiency is 60-63 based on the Preston guide. That means troyorr, you are calling one of two of your colleagues a liar, and me an idiot. I guess I can live with being called an idiot, but I'd be very interested to know which of the hvac pros are lying! Or "confused" if you prefer? Or is it a question of efficiency as new, versus efficiency at 30 years of age. What does *your* Preston guide say?

[Edited by uncleblaine on 10-20-2005 at 03:24 PM]

[wyounger]

125k in, 100k bonnet capacity means 80% efficiency running at steady state under perfect conditions. Calculating from bonnet capacity is by no means equivalent to AFUE, which considers standby losses, startup losses, etc. In other words, real world conditions.

Hell, I'm not even a pro and I know that. So maybe somebody should go back to fourth grade furnace class :D

[curry]

Originally posted by wyounger
125k in, 100k bonnet capacity means 80% efficiency running at steady state under perfect conditions. Calculating from bonnet capacity is by no means equivalent to AFUE, which considers standby losses, startup losses, etc. In other words, real world conditions.

Hell, I'm not even a pro and I know that. So maybe somebody should go back to fourth grade furnace class :D

Dude, sounds like you qouted right from GAMA.

But you are perfectly correct. There are many other things to consider than just dividing input by output.

[uncleblaine]

Thanks wyounger and curry. That makes me feel better. Being called an idiot is not nearly as distressing when the source is a 4th grade math whiz. :D

[tbox8098]

I will second that thought uncleblaine. Talk to you tomorrow

Travis

[kjones]

"Go back to your fourth grade math class. 125,000 in and 100,00 out. Sounds like 80%."

Wow, is it that simple?!? I've been waiting to hear that!That means my 50+ year old furnace that has a stamped metal plate saying 150000btuh in and 120000btuh out also has an 80% efficiency - cool!!!

"And old furnaces never lose efficiency. Or do they?"

I hope not, cause now that I know mine is an 80% I don't need to get a new one...

KJ

[troyorr]

I reread my post. I must have missed where I called my collegues liars or you an idiot. Go back and reread your original post. You ask about input and output. You didn't ask about anything else. If you divide output by input, you get a percentage. Now, try asking an informed series of questions on how to determine the btu requirements you need based on a specific set of guidlines we use to perform a heatload calculation and you'll find an answwer that will determine what size equipment you need. You can ask from now until hell freezez over about input/output of your furnace and the answer will always be 80%. Can't make it any clearer than that.

[kjones]

Hope the smoke clears soon.

Still would like to know what the book says about the estimated AFUE (not efficiency, eh?) for my 1953 vintage Premier GA150.

KJ

[Edited by kjones on 10-20-2005 at 09:08 PM]

[uncleblaine]

Originally posted by troyorr
I reread my post. I must have missed where I called my collegues liars or you an idiot. Go back and reread your original post. You ask about input and output. You didn't ask about anything else. If you divide output by input, you get a percentage. Now, try asking an informed series of questions on how to determine the btu requirements you need based on a specific set of guidlines we use to perform a heatload calculation and you'll find an answwer that will determine what size equipment you need. You can ask from now until hell freezez over about input/output of your furnace and the answer will always be 80%. Can't make it any clearer than that.

I'll grant that you did not use those words. But based on posts by others that followed, I obviously was not the only one to interpret them that way. My original post is below:

My 2-story home in central Minnesota currently has a Ruud HR-125JD gas furnace. Does anyone have any idea what kind of efficiency this model has? I've owned the home for 9 years, but I've no idea when the furnace was put in, though I doubt it is an original 1958 model.

It's rating is 125000 BTU/hr with 100000 BTU bonnet capacity. Can I use that as a wild guestimate for proper sizing of a new unit? Also, I intend on replacing the current junk US Steel windows as part of the entire project. Is it safe to assume my BTU needs should be less with energy star windows? I've got calls to set up estimates with the local Bryant, Trane, and Rheem dealers but haven't heard back yet. Given the approaching cold and rising NG prices, if they get back in the next few days I'll be pleased. I'm thinking I want to go 90+ efficiency on the furnace and replace my 3 ton(?) AC unit at the same time. I have a Trion electronic air cleaner and a Skuttle humidifier that I would like to be able to keep using as they are under 3 years old. Is this realistic or a pipe dream?

Where do I ask input/output questions? I do ask if I can use those numbers for a wild guess at sizing of a new unit, so perhaps you took that to mean output? And remember, I read those numbers off a plate not having any idea what meaning they held. That's why I was here in the first place. Of course sizing of a new unit even if based on 100K output is dependent on the efficiency of that new unit, is it not? By the time you added your post alluding to my mathematical abilities, the discussion had evolved a bit. There is several pages in the thread...

And if it matters, based on a heat load calc I received today, a furnace with 125K input would be *perfectly sized* for my house if it was 36 percent efficient given the heat load of approximately 45K. See, I really CAN do math!

And if your point was semantic in my use of the term "efficiency" rather than AFUE, then you were obviously just itching for an argument and I'm glad I could help.

[Edited by uncleblaine on 10-20-2005 at 09:17 PM]

[troyorr]

Thank you for clearing that up and pointing out my short comings. Just want you to know, I took a call from MENSA and they told me you weren't being considered for membership. However, I also took a call from Sesame Street and they told me they were considering you for the assistant position to help the Count. For your information, if you replace the windows, insulate the floor, walls and ceiling and install true thermally efficient doors, you could heat your house with a match.

[dan sw fl]

Originally posted by troyorr
For your information, if you replace the windows, insulate the floor, walls and ceiling and install true thermally efficient doors, you could heat your house with a match.

How many matches do YOU use to heat Your house each winter?

[uncleblaine]

Originally posted by troyorr
Thank you for clearing that up and pointing out my short comings. Just want you to know, I took a call from MENSA and they told me you weren't being considered for membership. However, I also took a call from Sesame Street and they told me they were considering you for the assistant position to help the Count. For your information, if you replace the windows, insulate the floor, walls and ceiling and install true thermally efficient doors, you could heat your house with a match.

Thanks troyorr. This really clears up the value of your opinions for me.

If energy efficiency in home heating is really as easy as you say, perhaps you should be in charge of national building codes.