Generator to power RV Air Conditioner

Thread Starter


Joined Jul 10, 2005
I have a generator that is rated at 5000 continuous watts, but I really don't have the best configuration on the outlets..

My generator is a Coleman PowerMate Maxa ER Plus with two NEMA# 5-15R Duplex 15 amp 120V plugs and one NEMA# L14-20R 20 amp 120/240 plug.

I have plugged my air conditioner into the 15 amp 120V side with a 30 amp RV to 15 amp adapter plug, but it will blow the 15 amp circuit when it gets above 110. Voltage looks good on the meter all the way until the circuit breaker blows.. I would like to use the 20 amp plug to power the RV so I don't have the 15 amp limit.

I have contradicting reports on the possiblity of wiring like this, can someone tell me if this is possible and how to wire it? I would like to make another adapter from the NEMA L14-20R to my 30 amp RV plug. I believe I can use the three wire system and just leave one of the 120V phases disconnected, is this true? Are the two 120V phases the connections across from one another?

If not, is there any other way to wire this generator to get more than the 15 amp service at 120V?

Thanks for the help,


Joined May 16, 2005
If I understand correctly, your dogbone is 15A male and 30A female, yes? Remember that the dogbone only changes connection configuration - it does nothing to change the actual amperage available. If you put 15A in, you get 15A out - even if it is through a 30A receptical.

Do you know the current draw of the AC?

Your assumption about the 120/240 outlet is correct. It would be possible to rig up a dogbone, but if it were my RV I wouldn't try it. I have a natural aversion to unbalanced split-phase supplies. You should too. That neutral carries the current difference between loads, and if one load is zero... Does your family ever stay in that RV?

I suggest selling your generator and replacing it with something like an Onan 3600 LP or a DeWalt DG4300 or DG6000. I know its not what you wanted to hear, but it is a safe (if costly) alternative.

Thread Starter


Joined Jul 10, 2005
I do have a cheap plug that I picked up at Walmart that is 15A Male to 30A Female. The 15A side is a standard wall plug, while the other end is a 30A RV Plug.. This works fine to run the trailer plugged into the home or plugged into the 15A side of the generator.

From what I have read the AC unit will draw 17A, but does surge when the motor kicks on.. My 15A circuit will run the unit on low, but not when the heat gets extreme. (over 110) I was hoping to run the unit on the 20A side of the generator but need advise on how to wire it.. If this is possible and safe it would delay the purchase of another 1000-2000$ generator..

When it gets real hot the AC will make the 15A breaker blow. Can you explain to me why you feel the unbalanced split phases supply is dangerous? Is there a way around this? I don't understand what this means..

If the generator can supply 15A 120V safely, why is it dangerous to use the 20 Amp plug to get 120V? Why do they call it a 120/240 plug if it is dangerous to wire it to use the 120V?

I had another person give me advise to run the 240 into the trailer and then use one phase to run the AC and the other to run everything else.. What is the difference in not using the other side? My trailer is very small and is mainly used to get out of the heat when I am at the racetrack.. When my family goes with me, we are in the mountains and will never need the AC, or generator.. All of the heat and such runs on Propane.

I want to be safe, but can't afford the new generator now..