btus-input vs output?

[MGM2]

I just got my last quote from a Lennox dealer. As some of you know, the recommended size for a new furnace has ben all over the place for my home. This guy is quoting for a 90,000 btu, which, by what all of you have been saying is way oversized. When I questioned him about it, I learned this tidbit of info - true or not?:

a 90,000 btu 80% furnace has an input of 90,000, but only puts out 63,000 btus. A 70,000 btu would put out 54,000, which maybe insufficient on coldest days. Furnace quoted is the G50UH36B-090.

He is also recommending a 3 ton ac, where everyone else has said 2.5. An XC13, which would be "increased by the coil to 14 seers".

No, he did not do a load calc. Said it's not the only thing to go by, judged windows, ducts, insulation, room sizes, etc, etc.

I was seriously considering his proposal, since the Rudd dealer hasn't called me back from last Friday, and the equipment specified (except for size) and price seem okay. But if I insisted on him recalculating my needs, and sizing properly, could I trust his install? Or should I just forget this one completely?

[selfemployed]

Gas furnaces are expressed in input. Oil is expressed in output.
90K 80% gas should be 90,000 x .80 = 72,000. 90k oil is 90k output. There are other things that can effect rated output. Thats the simple answer.

[MGM2]

Thank you for clearing that point up for me. Then he is correct in his statement, but still off on sizing .

[ampulman]

Thank you for clearing that point up for me. Then he is correct in his statement, but still off on sizing .

???

[MGM2]

???

Several other installers on here said there's no way my 1500 sq ft house would need a furnace that big. My estimates have been all over the place. It seems they're just guestimating, not doing load calcs.

[selfemployed]

I wasn't in on your origional post about the sizing, so I recommend this http://hvaccomputer.com/talkref.asp If you take the time to do it correctly there won't be any question about sizing.

[beenthere]

He doesn't want to, or doesn't know how to do a load calc. JMO

As said earlier, a 90,000BTU input 80% is 72,000 BTU output.
An 80,000 BTU input 90% would be 72,000 BTU output.

You might want to use teh hvac calc program and do your own, and decide from there who you want to use, if you can't find a comtractor to do a load calc for you.

[t527ed]

Furnace quoted is the G50UH36B-090.

just to throw another wrench into all of your figuring......... actual input of that furnace is only 88,000 btu's, 070 furnace wouldbe 66,000 btu input.
all Lennox furnaces are 22,000 btu's per burner.

if load calc is between the 2 sizes maybe a G60uh or G60uhv 2 stage furnace would be a better fit........

[beenthere]

That would still give outputs of, 70,400 for the 88,000 at 80% and 52,800 for the 66 at 80%.

And a house that may only need 36 to 45,000.