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  1. #1
    Join Date
    Jul 2008
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    Furnace capacity: Input vs Output?

    I recently had two Trane XR80 furnaces installed. They replaced a 75000/60000 Carrier and Goodman furnaces (80AFUE). I clearly specified to the contractor that I wanted Trane B, 60K furnaces as replacements. The contract we signed had a column marked only ‘capacity’, with 60k listed and ‘B’ model. Of the 4 B models, 3 have ‘nominal output capacities' of either 63-64k—the other has a 47k output. I have just discovered that what they installed were B models, but the one with 47,000 btuh output. All the Trane installation docs (Installers Guide which they gave me) and the docs on the Trane website clearly list ONLY ‘nominal output capacity’. The contractor insists that he uses ‘input capacity’. I do not find ‘input capacity’ specficially referred to in any Trane docs. The contractor insists that the ‘industry standard’ is to refer only to ‘input capacity’, even though his sales contract does not say either input or output capacity. I clearly was using the Trane docs to order 60k output, not input. I intended to replace my Carrier and Goodman furnaces with exactly the same capacity. Am I at fault here? Has the contractor take advantage of me? Is ‘input capacity’ the ‘industry standard’ for quoting furnace capacity? Thanks for the feedback.

  2. #2
    Join Date
    Mar 2005
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    burlington county n.j.
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    gas furnaces are all sold by input capacity.

    they are sized by output capacity determined by the afue ratings.

  3. #3
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    Standard is INPUT.

    Look at threads talking about furnaces. 99% of the time, you wil see XX,000 BTU XX%.
    That is BTU input and AFUE efficiency rating.

    How do you know the old furnaces were the right size?
    The 135,000 BTU output of the old furnaces may be more then your 3800 sq ft house needs.
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  4. #4
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    Jan 2004
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    Also, if you look at the lit on Tranes site. You will see that the model numbers are by input.

    EG: For your furnace, TUE1B060A9361A

    What you may have wanted was : TUE1B080A9361A
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  5. #5
    Join Date
    Jul 2008
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    8
    Thanks for the informative replies. However, my point is that if you do look on the TRane websites (http://www.trane.com/residential/pro...aces/XR80.aspx) the manufacturer lists ONLY 'nominal output capacity'. He does not list or clarfiy anythng about 'input capacity'. If you dig further (and again the contractor) gave me this written literature, the manuals show 'input btuh' and 'nominal output capacity'. You are correct--I wanted the '80' furnace model. But the furnace model has either 11-14 digits/characters in it. They simply changed a 6 to an 8 and I ended up with 47000 output rather than a 60000 output furnace. I did NOT intend--and never discussed with anyone--downsizing those furnaces. They worked just fine and this was part of a whole house package deal. Where did the 3800 sq ft number come from? I did not mention that? Thanks again. I think you can see that I the customer feel that I may have been 'tricked' here. Absolutely not making accusations, that's why I am asking questions. They say this is 'industry standard', but manufacturer lists only by 'nominal output capacity', sales contract lists only 'capacity' with no clarification of input or output. Customer ends up with 20% less heating capacity and a load calcuation was never done. Thanks once again.

  6. #6
    Join Date
    Apr 2007
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    6,285
    He may/may not have done you a favor by accident....you could verify that by a heat loss calculation.

    Describe your house to us.....just out of curiosity.

  7. #7
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    Mar 2005
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    burlington county n.j.
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    if anything it may have been a misunderstanding between you and your contractor, there is not enough difference in price between sizes of the same model to be worth "tricking" anyone over.

  8. #8
    Join Date
    Jul 2008
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    8
    THanks again gentlemen! Yes, I assume there can't be much difference in price but what is left for the customer to think. My major worry is that I have taken away 20% of heating capacity and never intended to do so. What do you mean that he may have done me a favor by accident? Natural gas prices are insane. It's a two story house with unfinished basement. About 14 SINGLE pane windows on each level. Very drafty. Walls R11 insulation only. Each of 3 levels is about 1400 sq ft. 2 story foyer, second staircase, fireplace often in use in winter (so that flue is open all night). So a lot of heat from main level of course just rises to second story. A lot of burden on downstairs furnace--its practically trying to heat the whole house it would seem. 47000 capacity (after I had 60000 on each level)--is that going to work? Won't a smaller furnace just run and run--and perhaps not last as long, or have problems from continuous running? How good are these small Trane XR80 furnaces? I bought Trane because it was one of 3 major manufacturers.

  9. #9
    Join Date
    Apr 2007
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    6,285
    Quote Originally Posted by capguy View Post
    What do you mean that he may have done me a favor by accident?
    May or may not. It would be hard for me to say it won't perform correctly. We'd have to know the heat loss from your home. How did the two old 60K furnaces perform on the coldest of days? Did they run constantly?


    Quote Originally Posted by capguy View Post
    Natural gas prices are insane.
    I agree so you would want to use the smallest furnace that can meet your needs. What those might be aren't determined yet.


    Quote Originally Posted by capguy View Post
    It's a two story house with unfinished basement. About 14 SINGLE pane windows on each level. Very drafty. Walls R11 insulation only. Each of 3 levels is about 1400 sq ft. 2 story foyer, second staircase, fireplace often in use in winter (so that flue is open all night). So a lot of heat from main level of course just rises to second story. A lot of burden on downstairs furnace--its practically trying to heat the whole house it would seem. 47000 capacity (after I had 60000 on each level)--is that going to work?
    That's a huge house. Not sure if it will work. Are you happy with your contractor? If so...since it sounds like there was a misunderstanding. Have him do a heat loss calculation on the home and see what it comes up with. Or get an independent contractor to do one if you feel the numbers may match to meet the current furnaces.


    Quote Originally Posted by capguy View Post
    Won't a smaller furnace just run and run--and perhaps not last as long, or have problems from continuous running?
    Yes one of the benefits as long as it's not grossly undersized...a more comfortable home. I wouldn't say it won't last as long. The furnace comes on for a brief period of time to heat the exchanger so you do not get cold drafts on start up. So for that brief period of time it's not actually helping your house out very much till the fan kicks on. Unless your not flowing enough air for the furnace or the temp rise is to high then you shouldn't have to worry about the life of the furnace.....they usually have good warranties on heat exchangers.


    Quote Originally Posted by capguy View Post
    How good are these small Trane XR80 furnaces? I bought Trane because it was one of 3 major manufacturers.
    That's a relative question to who your asking. If they sell them they will be wonderful. If they don't you may receive other answers. Are you happy with the warranty or the quality of them and the install besides the discrepancy in sizing? If so then they are great we just need to determine what your heat loss for the home is and then you'll be set.

  10. #10
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    Jan 2004
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    Lancaster PA
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    If you had asked me to install a 60,000 BTU 80% efficient furnace. And the furnace I'd of installed would be the TUE1B060A9361A, not the TUE1B080A9361A
    You confused the contractor. He did not trick you.
    Yes Trane list the outputs. But, Designers, Engineers, and Salesman use the Model number for BTU designation.

    The contractor is not at fault. You were not tricked.



    Not a bad guess on the size of your house, huh.
    Your old furnaces were sized by a ball park guess method. And I used one of those methods to guess at the size of your house. Turns out, that its smaller then I thought. I wasn't including the unfinnished basement.

    Close that fireplace damper, and your first floor probably needs less then 42,000 BTUs.
    Second floor probably closer to but under 48,000.
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  11. #11
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    Jul 2008
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    1) The two 60k furnaces (Carrier, Goodman) did heat the house fairly well. They did not have to run continuously. That's why I never intended to change capacity. Knew what I had, and wanted to stick with same. 2) House size: maybe not that huge these days. Houses seem be huge, but much better insulated, and everyone has double-pane windows now. Remember 2800 sq ft finished on two levels, basement is NOT finished. Winter here in southern TN lasts about 5 months (looking at my nat gas bills) and it's colder here than you might think. 3) So you think that if they are not undersized (again, especially that lower furnace which seems to take the brunt since of course heat rises) that running for longer periods of time would not shorten the life-span or result in mechancial problems? The old Carrier unit was actually 23 years old and doing just fine (had a maintenance contract), and I really had no problems with it. Again, just replaced both furnaces as part of a complete Trane heating-AC package deal (2 ac, coils, furnaces). Thanks.

  12. #12
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    Lancaster PA
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    Starting and stopping is harder on a furnace then long run cycles.

    I don't know what you call cold. When you say it gets colder then you think. I was thinking along the lines of 0°F.

    What dose suppise me. Is that in this day of high energy prices. You didn't go with higher efficiency furnaces. Or improve your homes envolope.


    Unfinnished basement doesn't add that much to the heat loss of the first floor.
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  13. #13
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    Jul 2008
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    Couple of clarifications: 1) In the case of the unfinished basement, it is exposed on two sides in what is called a 'walkout' or daylight basement in some parts of the country. So on two sides, there is only R11 insulation, and no heat down there. Temp gets pretty chillly down there all winter. 2) I did ask for a proposal on the 92 AFUE Trane furnaces. The prices was $xxxx/each higher. A thousand here, a thousand there, pretty soon it becomes just too expensive even with the ridiculous nat gas prices. Also, the salesguy put down the high efficiency furnace as a condensing furnace which meant they would need to run an outlet drain pipe through a wall 'which will just freeze up in cold weather and your furnace will then shutdown' all the time.

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