running air conditioner with generator

[cscarrett]

Does anyone know a way to calculate how big a generator I would need to purchase in order to run my household air conditioning unit? I figure I won't be able to run much else but If I can cool my house down a bit,I'll be a happy man.

[suemarkp]

I don't think there is a universal formula. It depends on whether you have a hard start kit, the type of compressor you have, wire size and length, etc. If its a large AC, it should have a Locked Rotor Amps (LRA) value on the nameplate. I think you'll need something that can do about half of this value in order to start the AC without damaging it. Baring that, I'd go for at least 2.5 times the nameplate amps (MCA or just amps, depending on the nameplate).

Because of the huge starting load and therefore the oversized generator, you can actually run more stuff once the AC has started. But I'd hope most of those other loads went away once the compressor begins to cycle on and off. You may be better off with a few portable AC's (but get 240V ones) to help even out the load instead of a large central unit.

[jeffo]

You should also consider installing a 'soft start kit'. Most central ACs have provisions for one to be installed. On my Trane, it plugs into the existing wiring harness. Basically it's a combination of extra capacitors and relays to reduce the starting current (and thus power).

Also, remember you also need to supply the furnace for the blower, thermostat (and air cleaner if equipped). Take into consideration the power requirements for these devices too when sizing the generator.

[Piper]

Volts X Amps = Watts

If your ac unit draws ten amp at 120 volts = 1200 watt generator to run it. As mark statedit takes additional power to start electric motors up to five times the amp draw on start up.