Any AC or engineering types out there that know of a simple formula or calculator to size an electric motor to an Ac compressor?
The problem is—– I got 2- 7.5 Ton (90,000 btu) compressors that need power. The 1st law of thermodynamics–“mechanical and heat energy are mutually convertable” obviously doesn’t apply after I do the math.
1HP=2546btu so 90,000 btu= 35+ HP —NOT
So I blow the dust off some 70’s AHRAE text books and get a formula using MEP (mean effective pressure) or Heat input method- and other nonsense that makes my head hurt.
I don’t need to be exact…. +-10%…. just doing some load inputs for generator sizing. Later on we’ll let the salesmen or installer size the package accordingly.
Replies
The problem with that formula assumes that the compressor is supplying all of the energy.
What it is doing is just transfering that much energy with a certain tempature difference.
IIRC my 24000 BTU AC calls for 15 amps. And if is an old 8.7 SEER.
Based on that I estiamte 56 amps. Probably a somewhat less with a 13 SEER.
But AC's are hard starting so you want to err towards oversizing the generator.
.
A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.