A/C on generator question

DelawareRick wrote:
I swapped black wires back to original locations, then ran both ACs. Both ran fine for at least, say, 45 minutes at which point I started tripping generator CBs to verify behavior. It is still the case that if either generator CB is off, neither AC will work.

At this point it's sort of academic... since we can make due with 1 AC while on generator, I'll probably just stick to running one rather than risk an issue running both. I'd just like to have an understanding of why both ACs stop working.

They both stopped working (also NO 120 power to the RV) because in your system, the 120 volt transfer box has 2 120 inputs from the Genset. BOTH Inputs must have 120 power to close the switch and power the RV. I still think you have a defective AC. probably the rear AC if you state you can run 1 AC and I assume that is the front one. Kill the AC that is running fine. Turn the other AC ON and see if it will run more than your 45 minutes to an Hour without tripping the breaker. Also, we need to know year/Brand/Model of RV. Do you have an Inverter/Charger? If so, that may be your problem. Years ago when they installed 5.5 or 6.5 Onan Gensets, they wired the Rear AC and the Inverter/Charger on the 2nd leg of the Genset. 6.5 onans had 2-30 amp breakers. 5.5 have the 30 and the 20. When the Power(120) is first applied to the RV, The Inverter/Charger goes into BULK charge mode and if the Internal charge rate has not been changed from the Inverter maker settings, THAT 12 volt charge rate will pull up to 10 amps. That means if you have the rear AC running and since you just started the Genset, that 20 amp breaker will have the rear AC(11 to 14 amps) PLUS the Inverter/charger at 10 amps which will be OVER the 20 amp threshold of the Onan breaker and will trip. When IT trips, the 120 Transfer kicks out. Also, If you do NOT have an Inverter/Charger, there may be some other hi amp appliances pulling current on that leg going over the 20 amp threshold. If you have the Inverter/Charger, the fix is to reset its bulk charge rate to a lower amp draw around 3 to 5 amps(AC amps not DC amps). Doug