A/C on shore power trips breaker after 30 minustes

OK, all electronic theories are out the window. Yesterday I had the shroud off the A/C and it was very hot in our area. I think it exposed the compressor and coils to more heat than it could handle. Today I put everything back and also cut away some of the grills in front of the exhaust radiator fins and coils. I read that it blocks the airflow and can reduce the cooling effect. I fired the unit up today and it has been running for over an hour. It is a bit cooler today but still plenty hot. 83 today and yesterday 99. I am not sure if there is a safety cutoff on this Coleman A/C but it would not surprise me. Thanks for all your help.

Disregard that time2roll, i supplied the wrong quote. Meant for the OP.

time2roll wrote:
Really need a volt reading in the RV and a clamp-on ammeter to do some actual diagnostics.

Although at least verify the fridge and water are off or set to propane only. If the battery was low that converter will also draw significant power for 30 to 60 minutes.

Check the output on that 30 amp generator plug.
U need a TT-30 socket on the generator , a 120v 30amp not a 240v 30 amp.
Its a different prong configuration.

From what I understand the ohms law is causing the voltage to lower because of the distance from the coach to the wall socket and then the fact that it is only 120 v. This load raises the amps and the A/C pulls more than 20 amps tripping the breaker. The inhouse generator eliminates all that load and provides more than enough amperage to support the A/C.

Really need a volt reading in the RV and a clamp-on ammeter to do some actual diagnostics.

Although at least verify the fridge and water are off or set to propane only. If the battery was low that converter will also draw significant power for 30 to 60 minutes.

I like to solve problems and this one is bugging me. I have a generator for power outages and it has a 30 amp output on it. I may just fire that up and hook up the shore power cable to it and see if it will keep the A/C going. I have a feeling that 20amps service is not enough even though it should be.

Ext cord going to 30 amp adaptor is too light.

You can get away with a 20 amp cord but it has to heavy enough gauge wire. 10-12 ga.


Or , Use the rv’s 30 amp cord direct to a 30 amp socket or use that 30 amp cord thru a 20 amp adaptor if you don't have a 30 amp socket at your home.

wolfe10 wrote:

wpatters1229 wrote:
What could be the difference between shore power and generator power?

Could be VOLTAGE.

What is voltage on that 20 amp shore power with extension cord with the A/C running?

Do you have an ATS? If so, have you checked that the connections are clean and tight and that the wires are not burned?

Please, before you go buy an extra/spare A/C, tell us what the VOLTAGE is with the A/C running!

wpatters1229 wrote:

It is just the internal breaker. The RV is in my driveway. I just replaced the extension cord (50 ft) with a heavy-duty gauge wire. I did feel the connection on the smaller cord where it connects to the adapter and it was warm. Maybe that smaller wire created too much load along with the A/C. Nothing else is running. The 30-amp breaker is for the whole RV. The rest of the breakers are all 15 amp. I have not tried the A/C with the larger cord. I think that may have been the problem along with the 99-degree heat here in CA. I am about to go turn on the A/C with the heavier cord to see if that was the problem. It takes about 20 minutes before the breaker trips.

When you say "heavy duty" is it a full blown 30amp RV cord or one of the orange extension cords. Even a good quaulity orange one is typically smaller gauge wire than a 30amp cord.

Also, how long is the total cordage. If you are stringing together 100+ft of cords, that's generally not good for running heavy loads.

This comes into play as smaller gauge wire and longer wiring rund will result in votage drop. When this happens, you get higher amperage and that can heat up the wiring which further reduces the voltage...if it's on the edge of popping, something like the battery charger kicking on may push it over the edge even though you didn't see or do anything.

If you have a multimeter, you should check the voltage at one of the RV outlets while the aircon is running. Ideally, it should be up around 120v. 110v or higher is OK. Down to 108v is marginal but technically in spec. Below that and you start to risk burning up the aircon compressor motor.

If you don't have a multimeter, you can pick up a voltage meter that just plugs into a wall socket. We have one that we leave always plugged in. When we set up at a new site, we typically take a look to see that the voltage is reasonable. Also, when we kick on the aircon, we check as it can pull the voltage down bye 4-5volts if the park power isn't strong.

OK, I started the A/C and it did the same thing. I am going on a month-long trip to Montana so I will see if a dedicated 30 amp in a RV park will work. I also ordered a backup portable A/C unit to keep me from frying. Worst case I can run the generator but that seems too disruptive for other RVers. I am thinking that I may not have ever run the A/C at home except to put a load on the generator to maintain the generator each month.