I inspected a new 3750 SQ FT house with two 44,000 BTU mid efficiency heaters with two 3 ton A/C units. I don't have a problem with the A/C sizes but what about the heaters? How many thousand BTU's per square foot is adequate?

Gonna have to run a heat loss/gain calculation for the building in the climate you're located to find out that answer.

Anything else is going to be a guess.

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Like DavidR said, need a load calculation to be sure but I would also be leary of a furnace that size having enough air flow to use with a 3 ton unit. Back in the dark ages, when sizing units in the Dallas area, we had to use furnaces that were way too big on the heating side just to get enough A/C tonage to do the job, but things may have changed a bunch since then.

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Jim Luttrall
Mr. Inspector.net, Inc.
Allen, Texas 75002

Tony,

I would have to agree with David. If you are in Mustang, Minnesota, then 88,000 BTU would certainly not be good enough.

I looked up the average temperatures for Mustang, Oklahoma and found that the January and February lows go down to the low 20s. Without having the information to do the calculations (even if I knew what calculations to do), I would guess that you are right and the heating system is undersized.

But, heck! Put on a sweater and run around that huge house and y'all'll be fine.

Jim is right as well. The smaller heating units generally do not have a large enough blower to push the air through and the coils will often freeze-up.

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