Manual J, 2.2 ton, round up or down?

[tealboy1]

What would you do based on this information, round up to 2.5 or round down to 2? I am a little worried about humidity control since it is a beach front condo so wonder if 2.5 might be too large, maybe it doesn't matter. The current system is 2 ton and is pretty popular but I haven't owned it long enough to know how well it performs during the worst of the summer

[udarrell]

I don't think we should be suggesting which way to go, the contractors in that environment, knowing your situation, are better positioned to advise you.

If you go to 2.5-Ton, I'd slow the blower for around 325 to 350-cfm per ton of cooling & get a room thermostat that has a swing cycle setting (I prefer the Swing setting TH) or a number of cycles per hour setting.

That way it would operate with a colder coil than the 2-Ton at 400-cfm per ton with not a lot of difference in sensible load performance. I don't have time to look it up!

Then set the temp variation from ON at say 78-F & OFF at say 74 or 75-F which will provide longer runtime cycles. The A/C needs to get the humidity down to 55% or below; 50% or below, is better...

You may need a low wattage floor type fan running in the conditioned area to stay comfortable throughout the temp spread.(?)

Then it depends on how much air infiltration your home has as to whether it will be able to control the humidity level.

[JonesHVAC-R]

What would you do based on this information, round up to 2.5 or round down to 2? I am a little worried about humidity control since it is a beach front condo so wonder if 2.5 might be too large, maybe it doesn't matter. The current system is 2 ton and is pretty popular but I haven't owned it long enough to know how well it performs during the worst of the summer

It says your relative humidity is 50%... is that what it really is or is that just something the person threw in there for the calculations?

I have seen designs that if humidity is a problem they will upsize the inside coil to a 2.5ton and utilize a 2ton outdoor unit. The larger inside coil helps with the dehumidification process.

[tigerdunes]

Teal

This is a HP system you are replacing?

What size is existing?

What is your location?

Unless there is an opportunity to significantly reduce load calc and depending on whether location is a high temp/high humidity July/August coastal location, I think it would be a mistake to round down. Go 2 1/2 ton and set blower speed on 350 CFM.

I simply don't like the idea of being borderline or undersized in a coastal location like the Gulf or Southeast.

IMO

[beenthere]

acguydcouch, this is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise here. Please apply to the AOPC today, thank you.

You can find the rules for posting and qualifications here (http://hvac-talk.com/vbb/showthread.php?t=957002).




Further infractions may result in loss of posting privileges.

[jimj]

You mite want to check your SHR. here is an explanation.
http://www.engineeringtoolbox.com/shr-sensible-heat-ratio-d_700.html

As your numbers would indicate a .845 SHR

[BaldLoonie]

Best not to look at tons but BTUs. Not unusual to find a "2.5" ton unit doing 27K of work.

[skippedover]

You mite want to check your SHR. here is an explanation.
http://www.engineeringtoolbox.com/shr-sensible-heat-ratio-d_700.html

As your numbers would indicate a .845 SHR

You took the letters right out of my fingers. He's used the default .7 SHR when he should be using .8xxxx. I came out with .823 but heck, .845 is close enough. That'll put it right about 2.0-tons I believe. I'm assuming, of course, that he's got the proper BIN data selected in set-up.

[tealboy1]

double post

[tealboy1]

Some of the posts are confusing to a novice like myself but I'll try to respond to a few questions (and very much appreciate the help). I currently have a Goodman 2.5 ton AH and a 2 ton Amana condenser outside. The location is Daytona Bch, Florida and the condo is directly on the Atlantic Ocean. The existing unit has done a so/so job of pulling humidity. It is 8 yrs old which is a long as they last on the coast. The recommendation is for a 2.5 ton AH and 2.5 ton condensing outside unit made by goodman, Straight cool w/ 8kw heat.

Two bidders recommended 2 ton which is popular in units my size but these folks did the manual J and said 2.2 suggests rounding up to 2.5 tons. However, they do not do a lot of work in my condo but a very good company.

I posted this vs. going w/ their recommendation b/c i want to get it right the first time and have some concern certain data in the manual j may be plug figures. Florida humidity is very high, especially in the summer and on the beach/coast.

According to the internet, RH in the summer is upper 60's at afternoon and upper 80's to 90's in morning

Last, the 2 ton is a 23000 btu and teh 2.5 is 27,300 btu cooling

[jimj]

I see they have your home listed as semi-loose, is it? How old is the home?

Manual J is a great tool, but as like most things BS in BS out. If there basing there tonnage numbers on what you have arrowed there wrong. As BaldLoonie has already said you need to go by the BTU's. Ask to see a Manual "S" or the extended ratings of the system they are recommending.

[skippedover]

If humidity control is your issue, then going up in size is going in the wrong direction. As I stated earlier, if the Wrightsoft Man "J" you posted has the correct background data used for the calculations, the a 2.0-ton is the best size. That said, if the old unit was having a tough time with humidity control at 2.0-tons, then I'd take the money from the price difference between 2.0 and 2.5 -tons and put it toward a whole house dehumidifier. That will keep the humidity under control and the 2.0-tons can then be dedicated to sensible heat cooling almost exclusively. No need to even tie the WHD into the ducted system. Let it operate independently and it will dehumidify even when the AC is completely off. What a deal!

[jimj]

If humidity control is your issue, then going up in size is going in the wrong direction. As I stated earlier, if the Wrightsoft Man "J" you posted has the correct background data used for the calculations, the a 2.0-ton is the best size. That said, if the old unit was having a tough time with humidity control at 2.0-tons, then I'd take the money from the price difference between 2.0 and 2.5 -tons and put it toward a whole house dehumidifier. That will keep the humidity under control and the 2.0-tons can then be dedicated to sensible heat cooling almost exclusively. No need to even tie the WHD into the ducted system. Let it operate independently and it will dehumidify even when the AC is completely off. What a deal!

:payattention:

[tealboy1]

don't know how loose the house is, it is a condo w/ a hurricane sliding door that seals perfectly and at the other end, there is a window that does have leakage but not real bad. It is only 1200 sf and as a condo, with a unit above, a unit below and units to the right and left, not much room for windows and doors. This also insulates the unit since it has limited directly sunlight exposure (just a few hrs in morning when sunrises).

Sounds like the 2 ton is the right one. Hard for me to know whether the inputs in the J are accurate since I don't understand all of it or have use of the tool to see how variables affect output. At this point, the biggest thing I am curious about is the SHR where someone said he used the std .7 but should be using .845 or .823. What is this figure and how will it change the recommendations? I presume it would suggest a smaller unit vs. larger?

[George2]

It says your relative humidity is 50%... is that what it really is or is that just something the person threw in there for the calculations?

I have seen designs that if humidity is a problem they will upsize the inside coil to a 2.5ton and utilize a 2ton outdoor unit. The larger inside coil helps with the dehumidification process.

Jonesy....I was taught (I'm not a tech mind you) that it's the reverse.

A smaller inside coil will get colder (better dehumidifcation).

[George2]

Best not to look at tons but BTUs. Not unusual to find a "2.5" ton unit doing 27K of work.

B.L. That's a great reminder.

[George2]

You want to make sure to get a "variable-speed" A.H. with the ability to have a dehumidifing control. Carrier/Bryant have nice systems. The heating will be staged
(quieter) also.

[udarrell]

don't know how loose the house is, it is a condo w/ a hurricane sliding door that seals perfectly and at the other end, there is a window that does have leakage but not real bad. It is only 1200 sf and as a condo, with a unit above, a unit below and units to the right and left, not much room for windows and doors. This also insulates the unit since it has limited directly sunlight exposure (just a few hrs in morning when sunrises).

Sounds like the 2 ton is the right one. Hard for me to know whether the inputs in the J are accurate since I don't understand all of it or have use of the tool to see how variables affect output. At this point, the biggest thing I am curious about is the SHR where someone said he used the std .7 but should be using .845 or .823. What is this figure and how will it change the recommendations? I presume it would suggest a smaller unit vs. larger?
Well, I'm thinking a 1200-sf condo with humidity being the critical factor, I would think, from here, that a 2-ton should handle the load.

You need a TXV metering device on that indoor evaporator coil set at around 8-F super heat. A thermostatic expansion valve will keep the coil properly fed to keep the coil colder especially during lower temps in the 80 to 85-F ranges.

You could experiment with using 350-CFM per ton of cooling, that will help with getting the coil colder, or 700-CFM with a 2-Ton condenser.

High humidity creates a heavy heatload on the indoor coil & if the combined sensible & latent heatloads are too high for those smaller high-SEER compressors, it could push the larger evaporator coil above the condensation dew point. Therefore, I would try 700-cfm with the 2-Ton condenser with the 2.5-ton indoor coil; that larger coil will tend to absorb more total heat.

The system needs longer operating runtimes to dehumidify... with 2.5-Ton the runtimes may not be long enough. It is your decision though...

Also, the room thermostat with the swing setting is always useful toward achieving the longer runtimes that do the best job controlling the humidity.

A lot of good advice offered; if the 2-Ton can't control the humidity, follow advice given above, get & use a dehumidifier...

[Stamas]

How often are you using this condo? Is it your 2nd home, rental? The humidity problems we see are from the air conditioner being turn of or set on high when the owners leave. Then the condo, home stews in the heat and moisture. Secondary humidity control like mentioned is a way to cut down on that.

[JonesHVAC-R]

Jonesy....I was taught (I'm not a tech mind you) that it's the reverse.

A smaller inside coil will get colder (better dehumidifcation).

The larger coil inside allows for more air to be passed accross it therefore more dehumidification. You just need to make sure you have proper system charge.

[JonesHVAC-R]

The Whole Home Dehumidifier is also a great idea...:.02:

[beenthere]

The larger coil inside allows for more air to be passed accross it therefore more dehumidification.

400 CFM is 400 CFM, regardless of coil size.

[JonesHVAC-R]

400 CFM is 400 CFM, regardless of coil size.

I'm pretty sure George gathered what I meant, especially after udarrell's post... However, your comment would be correct... 400 CFM is 400 CFM.

[George2]

I'm pretty sure George gathered what I meant, especially after udarrell's post... However, your comment would be correct... 400 CFM is 400 CFM.

Jonesy....

I still believe the larger coils take longer to get cold. The higher efficiency units must run longer (be sized smaller) to give them a chance to dehumidify.

The older A/C units could cool (dehumidify) 10 times better.

What some of the new furnaces do is slow the blower down on start-up for 2-3 minutes and gradually increase the blower speed so the coil doesn't freeze.

The manufactures have finally figured it out.

[Special Ed]

Wrightsoft makes good load calc software but as previously mentioned, "BS in = BS out...."

First & foremost, I see the weather parameters programmed into the calculations may be a little off, i.e., the average outdoor temp should be set a little higher as should the %RH. In Jacksonville, where I'm at, we figure the temp to be 95 degrees, on average.

Now, I haven't seen or been in the structure in question so I don't know if you have condos on either side of you or if it's an end, if you're upstairs or downstairs, or even what direction it's facing, all factors which must also be taken into consideration.

But if I were to guess - & that's all this would be - I'd say you'd need a 2.5ton system, because 600sq ft/ton would seem to be a stretch at best for this climate.

Also, as the great Baldloonie mentioned you should look more at the Btu's of a particular system....

[skippedover]

What we're all discussing here is the entire system design question. That takes a lot of training and/or knowledge to get the proper end result. The attached document gives you the steps needed to properly size a system. Saves me from re-typing it over and over. Trust me to say that after taking many classes and/or reading the various manuals, obtaining some significant test equipment and applying it all, you can do an excellent job of proper sizing. For each step skipped, the 'guess factor' increases. I stand by my previous; if a 2.0-ton has been doing the job fairly well but not ideally, then a whole house dehumidifier along with a new 2.0-ton system and ECM blower motor should do a fantastic job.

If you do not understand the relationship of Sensible Heat to Latent Heat or the impact of Dew Point on a system, then you definitely need to get back or into the basics of cooling, from whence all of us have spend considerable time and continue to do so.

[udarrell]

Skippeydover,that is an excellent pdf.
Wouldn't it be great of every contractor followed those steps...

Then if they did the actual equipment install applying the proper steps, we'd have some real good performing systems.:cheers:

[George2]

Skipper and U.D.

If there was one contractor in our town that did just one of those ideas listed on the pdf, I would have a heartattack.
They will worry more about putting on booties (to make an impression). What ever size ur equipment is, guess what you'll be getting again?

[Special Ed]

And I doubt most contractors on even this forum do every single one of those steps. I know we don't.

For instance, since most co's have a relationship w/one, maybe two, mfgs I am almost certain not even skippedover does a manual S.

I think more & more co's are doing manual J's & D's, though.

[jimj]

Skipper and U.D.

If there was one contractor in our town that did just one of those ideas listed on the pdf, I would have a heartattack.
They will worry more about putting on booties (to make an impression). What ever size ur equipment is, guess what you'll be getting again?

The HVAC world is changing, you mite be surprised!:.02:

[George2]

The HVAC world is changing, you mite be surprised!:.02:

Yes, there are a few (because of energy rebates) that will do a Manual J. But where I live, the power company doesn't, so no one does.

Our power company, in 2014, is going to (finally) implement some procedures that will force contractor to "stand at the plate"

[jimj]

Our utility now requires BPI certification to be part of there rebate program, they have required manual J's for a number of years even though most being done were bogus. They now have a QA inspector and he has most (as in all) of our competitors crying like a bunch of babies because they have to play by the rules.:grin2:

[udarrell]

We have a lot of good advanced test instruments with which to do the work right, however, I have not seen one HVAC contractor tech use a single instrument to even check actual air flow or even check static pressure.

IMO, we have a sorry situation in far too much of our chosen field of work; that is why I believe the customer needs to be educated concerning what constitutes a proper job; even if it's just a service check-up.

There are basic things that deserve being routinely checked; many problems can be observed as not functioning properly even before using test instruments.

It seems that getting in there & getting out in a hurry & doing the least they can is the M.O. of far too many.

IMO, we need an enforced "Best Practices," in all areas of our work.
The SEER Rating gets too much emphasis, & the things like the building, duct system, & the air flow, that make the big difference in actual energy & utility savings go totally over-looked.

How many customer's say that high SEER efficiency didn't save on my utility usage;too many; because all the most important elements toward real energy savings were ignored. I don't like saying it; but it needs saying... Doing it RIGHT results in more profit for everyone.

[jimj]

We have a lot of good advanced test instruments with which to do the work right, however, I have not seen one HVAC contractor tech use a single instrument to even check actual air flow or even check static pressure.

IMO, we have a sorry situation in far too much of our chosen field of work; that is why I believe the customer needs to be educated concerning what constitutes a proper job; even if it's just a service check-up.

There are basic things that deserve being routinely checked; many problems can be observed as not functioning properly even before using test instruments.

It seems that getting in there & getting out in a hurry & doing the least they can is the M.O. of far too many.




IMO, we need an enforced "Best Practices," in all areas of our work.
The SEER Rating gets too much emphasis, & the things like the building, duct system, & the air flow, that make the big difference in actual energy & utility savings go totally over-looked.

How many customer's say the high efficiency didn't save on my utility usage; because all the most important element toward real energy savings were ignored. I don't like saying it...


Well said Darrell. I do believe there is a change happening in our industry for smart progressive contractors that are aware of HP building, for those that aren't, there will always be customers looking for that cheap price.:whistle:

And yes Darrell there are contractors out there that are looking to do things correctly that will, and are beginning to take market share from those that are the blow and go types.

[second opinion]

Well said Darrell. I do believe there is a change happening in our industry for smart progressive contractors that are aware of HP building, for those that aren't, there will always be customers looking for that cheap price.:whistle:

And yes Darrell there are contractors out there that are looking to do things correctly that will, and are beginning to take market share from those that are the blow and go types.

I would also agree the customer needs to be informed and demand competency from the contractor and not be forced into making an uninformed decision based upon a maintenance tech promoting sales.

Few companies actually require there technicians to be technically knowledgeable, and a lot of this can be due to the lack of competency of the owners themselves.

[rickboggs]

What was the question? Just kidding! Your answer is found in the "Expanded Data" of the equipment.

Your "J" says these are your design conditions
91 degrees outside temp
75 degrees inside temp
50% indoor humidity

Your "J" says this is your load
22267 btus total
18324 btus sensible
3943 btus latent

Now, looking at one brand's expanded data using your design conditions... you know, your indoor temp/humidity and outdoor temps

Their 024 model @ 950cfm delivers
21900 btus total
16900 btus sensible
5000 btus latent
I would not choose this model, too low sensible capacity and too high latent capacity

Another brand's expanded data using the same design conditions
900cfm
22100 btus total
18300 btus sensible
3800 btus latent
I would think about using this one, although low....

Manual S recommends not oversizing more than 15%, which in your case is 22601 total btus. So, if you upsize....

the first brand's 030 model
25800 btus total
18100 btus sensible
7700 btus latent
too big

the second brand
030 model
800cfm
26200 btus total
20000 btus sensible
6200 btus latent
too big.

the second brand
030 model
1000cfm
27300 btus total
22400 btus sensible
4900 btus latent
too big

All this to say, if you weren't bored out of your mind... I would be, there's a little more to choosing equipment size.

Did you notice that a 2 ton (024 model) is not a 2 ton (24000 btus). Or a 2.5 ton (030 model) is not a 2.5 ton (30000 btus). And cfm changes performance.

I guess my answer is, you need a contractor that knows what to do with that "J" form... he'll use the numbers inside the numbers to select the equipment and cfm to match your application (Manual S). When he does this, don't compare his price with the dude that has no clue.

[rickboggs]

Don't mind the post, I'm just talking to myself.

Rick, "You know, Rick?"
Rick, "What, Rick?"
Rick, "This thread is really, uh, confusing."
Rick, "Yep, confusing."
Rick, "These dudes are so smart, but I don't understand what they're saying..... you know, weather data, SHR, humidity, CFM, Manual J, Manual S, extended data, pdfs here, links there.... how do you put it all together to decide which equipment to install?"
Rick, "I know what you mean. If someone would talk to me like I'm a home owner and not like I'm an engineer!"
Rick, "RICK, how do you expect to understand how all this data goes together and then choose equipment when these dudes spent years of studying and have years of experience?"
Rick, "?, some of these dudes can do it."
Rick, "Ok, should the dude upsize or down?"

[TwincamDave]

Something different to ponder, have you considered ordering the unit with "coated coils" ? probley double the life of your outdoor equipment.

[beenthere]

Don't mind the post, I'm just talking to myself.

Rick, "You know, Rick?"
Rick, "What, Rick?"
Rick, "This thread is really, uh, confusing."
Rick, "Yep, confusing."
Rick, "These dudes are so smart, but I don't understand what they're saying..... you know, weather data, SHR, humidity, CFM, Manual J, Manual S, extended data, pdfs here, links there.... how do you put it all together to decide which equipment to install?"
Rick, "I know what you mean. If someone would talk to me like I'm a home owner and not like I'm an engineer!"
Rick, "RICK, how do you expect to understand how all this data goes together and then choose equipment when these dudes spent years of studying and have years of experience?"
Rick, "?, some of these dudes can do it."
Rick, "Ok, should the dude upsize or down?"

2.5 tons. Many 2 ton units will have trouble meeting his sensible load.

[rickboggs]

jimj, can you explain the list under the "General Design Values" heading at the link you gave? I don't understand.

beenthere,
Many 2 ton units will have trouble meeting his sensible loadCan we talk about the procedure of deciding on a piece of equipment?

[SandShark]

Sizing the system based on Manual J data for design conditions, along with choosing the proper equipment based on Manual S and equipment SHR is certainly the way to go. But, what happens under part-load conditions when the occupants are away during the week, the thermostat is set at 82°F, the ambient temperature is 78°F, the dewpoint is 74°F and the system runs once or twice an hour for 5 minutes at a time? Wouldn't you all agree, as has been suggested, that a dehumidifier is a necessity?

[surenuff]

go 2.5 tons, and use a two stage cooling system if possible. Should work really great. Of course we need to pick the right equipment to best match load conditions. There should be some things that could be done to help lower that heat gain some and would help even more. If the load calc is right, unit would run on low most of the time and only be at full capacity a very little amount of time.

[rickboggs]

Of course we need to pick the right equipment to best match load conditions.
How do we "pick the right equipment to best match load conditions?"

[surenuff]

How do we "pick the right equipment to best match load conditions?"

you pick equipment that has the amount of capacity for the sensible and latent load of the structure, and match it up with an air handler/furnace that will match the heat loss.

[rickboggs]

you pick equipment that has the amount of capacity for the sensible and latent load of the structure, and match it up with an air handler/furnace that will match the heat loss.I'm a homeowner, you're selling me a piece of equipment. Show me the reason why you came up with the piece of equipment you chose for my home (your procedure for equipment selection).... use the load on post #1.

[surenuff]

I'm a homeowner, you're selling me a piece of equipment. Show me the reason why you came up with the piece of equipment you chose for my home (your procedure for equipment selection).... use the load on post #1.

Am I missing something? if you were the home owner, and you had that heat load calc in your hand, and the contractor told you the equipment he was going to put in your house was the best/closest match for the heat load, then what more are you the homeowner going to want to know? Does the system have the sensible capacity? Does the system have the latent capacity? Is the SHR of the equipment going to be right for latent/sensible loads? Is the duct work going to be correct for the airflow? Is it the right color to match the carpet?

[beenthere]

jimj, can you explain the list under the "General Design Values" heading at the link you gave? I don't understand.

beenthere,Can we talk about the procedure of deciding on a piece of equipment?

The equipment must first be able to handle the sensible load. All brands have a performance list/chart, that will tell you the sensible and latent capacity of the condenser and coil match ups, at different CFMs.

A moe indepth discussion of equipment selection can be one in the pro forums, or tech to tech forums. So that the OPs thread doesn't get too hi jacked.

[rickboggs]

udarrell's Post #33 speaks about education, education, education.... Here is a legitimate question by the original poster "should I upsize or go down?" Instead of the pros saying... "Go up!".... "Go down!" explain why. Explain why this mysterious manual S says UP or Down, or this SHR says UP or Down, explain why you're worth more than the jack-leg the home owner compares your price with.

Sorry you feel the thread is high jacked, but I would need better answers than what's been given.

[jimj]

udarrell's Post #33 speaks about education, education, education.... Here is a legitimate question by the original poster "should I upsize or go down?" Instead of the pros saying... "Go up!".... "Go down!" explain why. Explain why this mysterious manual S says UP or Down, or this SHR says UP or Down, explain why you're worth more than the jack-leg the home owner compares your price with.

Sorry you feel the thread is high jacked, but I would need better answers than what's been given.

Essentially, it boils down to a few basic steps:
1.Calculate the heating and cooling loads using Manual J.
2.Estimate the target airflow, for cooling equipment that is based on the home’s sensible heat ratio (SHR), which is derived from dividing the sensible load by the total load. For heating it is based on the manufacturer’s design temperature rise guidance.
3.Search the equipment manufacturer’s performance data for equipment that will meet the heating and cooling loads. Do not use the AHRI cooling equipment performance data unless the home has an outdoor design temperature of 95 degrees F, and the indoor design conditions are 80 degrees F at 50%Rh (67F EWB). The manufacturers produced expanded equipment performance data provides equipment capacity ratings at your design conditions.
4.Evaluate possible HVAC system combinations. At this step you should evaluate system capacity at (or close to) the target airflow derived from Step 2. The cooling equipment should be very close to the total cooling load while meeting the sensible and latent loads. Heating equipment should meet the heating loads. Both heating and cooling equipment should not exceed the sizing requirements set in Manual S.
5.Select the system that best meets the home’s needs.

[jimj]

udarrell's Post #33 speaks about education, education, education.... Here is a legitimate question by the original poster "should I upsize or go down?" Instead of the pros saying... "Go up!".... "Go down!" explain why. Explain why this mysterious manual S says UP or Down, or this SHR says UP or Down, explain why you're worth more than the jack-leg the home owner compares your price with.

Sorry you feel the thread is high jacked, but I would need better answers than what's been given.

Rick I have given several of my customers and GC's this book by ACCA, its called Bob's house and should be read by every A/C contractor and home owner looking for a new system or building a new home.

Want to understand Manual J,S,D,and T and how they all work together?
Here ya go!
http://www.acca.org/store/product.php?pid=32

[beenthere]

udarrell's Post #33 speaks about education, education, education.... Here is a legitimate question by the original poster "should I upsize or go down?" Instead of the pros saying... "Go up!".... "Go down!" explain why. Explain why this mysterious manual S says UP or Down, or this SHR says UP or Down, explain why you're worth more than the jack-leg the home owner compares your price with.

Sorry you feel the thread is high jacked, but I would need better answers than what's been given.

Already said that a 2 ton would have trouble meeting his sensible load.

[surenuff]

udarrell's Post #33 speaks about education, education, education.... Here is a legitimate question by the original poster "should I upsize or go down?" Instead of the pros saying... "Go up!".... "Go down!" explain why. Explain why this mysterious manual S says UP or Down, or this SHR says UP or Down, explain why you're worth more than the jack-leg the home owner compares your price with.

Sorry you feel the thread is high jacked, but I would need better answers than what's been given.

The homeowner only asked us if he should go up or down. In a lot of cases, the home owner don't even want to know about SHR, latent gain, sensible gain. And as far as explaining it to you, it seems like you just want to argue. What does that * mean by "professional member"? WHy did you not explain this to the OP?

[rickboggs]

jimj,
Now see, this what I'm talking about. We begin with airflow.
Using the load from the OP, what is my target CFM?

[rickboggs]

jimj,
I thought about buying the Bob book. Sounds like a good one.
And I bet your contractors love you.

surnuf,
not arguing, just asking you why... sorry I offended you.

[surenuff]

I read Bob's House. It was a good book.

[surenuff]

jimj,
I thought about buying the Bob book. Sounds like a good one.
And I bet your contractors love you.

surnuf,
not arguing, just asking you why... sorry I offended you.

no offense. I just could not understand what you were asking from me. In most cases, your average homeowner just wants to be cool. They don't want to know that much detail and in most cases, they would not understand it if you told them. I did understand that you felt we all should have done a better job in answering the OP. But I did not understand why you did not just explain the info you felt we were leaving out.

[rickboggs]

surenuf,
Post #36 has a little explanation.

In most cases, your average homeowner just wants to be cool. They don't want to know that much detail and in most cases, they would not understand it if you told them.And that's why you need communicate the reason your compressor failed is because your unit is too big, your return air and supply ducts are too small. When you explain why with a Manual J, Manual S, Manual D, and you have drafts and stale air because..... Manual T. Then this alphabet is not such a mystery to the customer. The customer can see why your price can not be compared to Jack Leg Cooling & Heating Inc. who has no clue and slapping in what he's pulling out. You'd be surprised what a costumer will understand if you speak so the customer can understand.
I have many meetings at the kitchen table explaining why.... your mold is because of this "J"..... the master bedroom is hot because of this "D"..... you have dust around your supply grilles because YOUR FILTER SURFACE AREA IS TOO SMALL. And around the conference table... Mr contractor, your high performance icf walled, encapsulated attic, home has mold on the walls because J, D, and T.

Proverbs 22:29 NKJV
Do you see a man who excels in his work? He will stand before kings; He will not stand before unknown men.

Be prepared to give an answer.

tealboy1, my weather data has Daytona Intl AP at 93 degrees and your load says you don't have a humidity problem at peak conditions, the opposite of what you've said. Must be humid in part load conditions (unit not running). Upsizing will aggravate these conditions. This is where the kitchen table comes in. Bin Data (how many hours my unit will be oversize and undersized). Dehumidifier? Tint windows? Caulk? Ceiling fan? Kitchen table!
Ok.... I'm done.

[surenuff]

surenuf,
Post #36 has a little explanation.
And that's why you need communicate the reason your compressor failed is because your unit is too big, your return air and supply ducts are too small. When you explain why with a Manual J, Manual S, Manual D, and you have drafts and stale air because..... Manual T. Then this alphabet is not such a mystery to the customer. The customer can see why your price can not be compared to Jack Leg Cooling & Heating Inc. who has no clue and slapping in what he's pulling out. You'd be surprised what a costumer will understand if you speak so the customer can understand.
I have many meetings at the kitchen table explaining why.... your mold is because of this "J"..... the master bedroom is hot because of this "D"..... you have dust around your supply grilles because YOUR FILTER SURFACE AREA IS TOO SMALL. And around the conference table... Mr contractor, your high performance icf walled, encapsulated attic, home has mold on the walls because J, D, and T.

Proverbs 22:29 NKJV
Do you see a man who excels in his work? He will stand before kings; He will not stand before unknown men.

Be prepared to give an answer.

tealboy1, my weather data has Daytona Intl AP at 93 degrees and your load says you don't have a humidity problem at peak conditions, the opposite of what you've said. Must be humid in part load conditions (unit not running). Upsizing will aggravate these conditions. This is where the kitchen table comes in. Bin Data (how many hours my unit will be oversize and undersized). Dehumidifier? Tint windows? Caulk? Ceiling fan? Kitchen table!
Ok.... I'm done.

trust me Boggs, when I am doing service work or changeout, or even new installation, my reasoning for what I am doing is based on fact gathered from facts. If the homeowner wants to know more about where I came up with the fact that his unit is oversized for example, I will pull out the facts and show him. In most cases I have found that a load sheet with all of those numbers on it give them a deer in the head light and a "I"m sorry I asked look in their eye. But the ones who are not scared by those figures don't need me to explain anything except what equipment choices they have to satisfy the load. The others just want to know and be told that the correct equipment will be put in. They trust me or they don't. You are making valid points, and I am not trying to argue with you either. Maybe we have primarily dealt with customers of a different learning level. And, I also guess that since my business has been due to a large part on referal, the customers I have had trusted me from the go. THat has maybe kept me from having to explain in great detail why I was doing what I was doing. I have a almost non-existant call back ratio, and a very high customer satisftion rate, thus the high referal. I know you must be a good tech too from what I am reading.