Generator Recommendations

No, nothing else was turned on, I was doing a detailed energy audit, measuring each load one at a time. It’s typical for a/c compressor loading to vary significantly with temperature differential between the evaporator and condenser. That’s why folks can find that a low power generator will start and run their a/c units initially but not after a second or third cycle.

In the dc (direct current) world power used (watts) = volts x amps. In the ac (alternating current) world it’s not that simple, because both voltage and current are constantly changing. If the current is not changing in phase with the voltage then the power used is less than the volts x amps. The ratio of power divided by volts x amps is the power factor. Typically in motor loads like your a/c compressor the current lags behind the voltage so the power factor is less than 1. In resistor loads like your water heater element the current and voltage are in phase and the pf is very close to 1.

It’s useful to know what the power factor of a load is for a couple of reasons. One is that you can’t just use your clamp on current meter to measure power used in ac loads. The other is that if you’re running a load with a low power factor on a generator you could overload the generator electrical circuit and trip it’s breaker while still having plenty of power available from the engine itself.

At a pf of .95 the roof ac is pretty good for an a/c compressor so you could expect that the genny electrical circuit and engine will be pretty well balanced and one won’t give up much before the other.

When I ran my AC with my 2000i Honda, I only ran it on low but I turned on the fan first let it run for about 5 min to cool the unit then I kicked in the compressor After a very short time the AC dropped down to 1480 watts.

Originally posted by podwerkz Originally posted by offgrid Just for the sake of being thorough, it’s also possible that my 2015 vintage Dometic roof air isn’t as efficient as the unit in your rpod. What year is yours? It's a 2019, with a standard 13.5 Dometic roof air.   There was no manual for the roof A/C unit in my paperwork, but I think I found it on the Dometic webpage, and it seems to show 1762 running watts. Hmmm....maybe the lower line voltage meant less wattage, duh, or maybe I need to do another test with a higher heat load. Or maybe the kill-a-watt meter is off by a few hundred watts.  Things get curiouser and curiouser....