Community Forums

Murphy · 08-14-2007, 03:12 AM

My friend has her motor home parked at my house and plugged into 30 amp. Some times the back air works but will cut off and only blow air. The front one comes on for about 2 to 3 mins. then shuts the breaker in her motor home off. It is a 98 Georieboy 36ft with Duo Them by Dometic conditioners. The plg comeing from the house is on its own line with its own breaker and it never cuts off our breaker only the one in the front of moter home. The back breaker doesn't cut off but the comprssers don't seem to run right. Any body have any idea whats going on. Please help!! Thanks

Murphy · 08-14-2007, 03:12 AM

My friend has her motor home parked at my house and plugged into 30 amp. Some times the back air works but will cut off and only blow air. The front one comes on for about 2 to 3 mins. then shuts the breaker in her motor home off. It is a 98 Georieboy 36ft with Duo Them by Dometic conditioners. The plg comeing from the house is on its own line with its own breaker and it never cuts off our breaker only the one in the front of moter home. The back breaker doesn't cut off but the comprssers don't seem to run right. Any body have any idea whats going on. Please help!! Thanks

Gary RVRoamer · 08-14-2007, 10:13 AM

Welcome to irv2, Murphy.

What is going on is that 30 amps is simply not enough power to reliably run two air conditioners. Each one needs about 12-14 amps to run it s compressor continuously but each also requires much more (25+) to start the compressor for each cooling cycle. When one a/c is running its compressor, there is not enough left over for the second one to start up. The fans can run, but the compressor cannot.

You didn't mention the brand of motorhome, but it sounds like it has a built-in load management system that tries to run the two a/c's alternately. When the compressor is running on one, it does not let the other compressor try to start and the second a/c just blows air. If the front a/c is between compressor cycles, the rear may have a chance to start its compressor and then the front cannot run until the rear compressor stops. And so on.

As for the breaker in the motorhome tripping, she is probably getting too low a voltage inside the rig, which causes the current (amps) draw to increase to the point where a breaker trips. You did not say what breaker trips - is it a 15 or 20A breaker for the front a/c or some other one? Or the main breaker in the rig?

By the way, does the motorhome have 50A service or 30A? I'm guessing it is 50A and she is using a 30A adapter at your place, but it wold be helpful to know for sure.

Murphy · 08-15-2007, 04:37 AM

Hi, the motorhome is a 36ft Georgieboy. It has 50 amp hooked to a 30amp plug and then plugged into our 30amp house plug. We don't try to run both airs at one time. We shut the air,fan thermostat off and then try to run the frount. It will run for 2 or 3 min the shut down the 20 amp breaker on her home. But when we shut down the front and turn on the back it will run for a long time until the hottest time of the day 4pm to 630 pm then the comprsser shuts down and only blows hot air. I had a 38ft home that we plugged in to the same 30amp from the house and used it for guests that stayed in it for about 5 days in the summer and never had any problems with one air running. Hope this helps some. thanks for any help you can give me.

GaryKD · 08-15-2007, 06:21 AM

Are both A/C units the same BTU size? Sometimes the rear is a smaller BTU than the front. This would make sense based on your last post.

Based on your last post, the compressors both start and run okay. It sounds like the A/C units, for what ever reason are pulling more electric than is avaialble, from the house.

Does the coach have a generator? If so can you run the A/C successfully with the generator when the A/C will not run with the house electric? If you can to this test, it might start us on a more focused path to provide help.

There can be no comparrison made about running another coach successfully and now this coach will not run. There are too many differences between coaches.

Gary RVRoamer · 08-15-2007, 10:59 AM

Based on your further description, I suspect the front a/c is larger btu than the rear and is also not running efficiently and drawing too much power. Low refrigerant, failing compressor/motor, etc. could be the cause.

Since the house breaker is not tripping, the total amperage must be under 30 (assuming the 30A plug is properly protected by a 30A breaker). I'm guessing that your friends power cord or 50/30 adapter is corroded at the contatcs (or internally at the plug) or the wires are partially broken, causing a voltage drop when the a/cs run. That will increase the amp draw and could be enough to trip the coach's 20A breaker for that circuit.

If the Georgie Boy has an automatic transfer switch, run the generator and see if the a/c will run OK. The auto transfer switch eliminates the power cord and 50/30 adapter from the equation and will narrow down the possibilities. But if the motorhome requires that its power cord be plugged into the generator outlet to use the genset, then running on the generator won't prove much. Still worth a try, though.

Murphy · 08-16-2007, 02:46 AM

She has to plug in to her coach to run the generator. She did this and they seemed to run fine but she didn't run it for very long. My guess is the front is bigger then the back. If she plugs up to 50amp do you think it will they will run like they should or may there still be an issue?

GaryKD · 08-16-2007, 06:34 AM

To confirm the electric from the house is not enough for the coach, let the A/C run for an hour (on the generator) after they have failed on the house electric. If the A/Cs run okay on the generator, the problem is the house electric (30 AMP). If the A/Cs run on the generator, then if she plugs into a 50 AMP service she should be fine.

I think we have this narrowed down to the house electric. Not to confuse the issue, but it has not been mentioned about the distance of the power cord to the house 30 AMP. Is the coach power cord the entire length of the cord from the coach to the 30 AMP power; or is there an extension cord being used to get power from the house?