Camper AC breaker trips only on generator

[Medicrn82]

I have a 2020 keystone passport GT 29 RL. We are boondocking with a 30 amp generator. It’s 100 degrees out during the day, and AC runs fine all day. At night, the 20 amp ac circuit breaker in the camper trips. Not the generator breaker. Water heater is not on. The only other thing running is the fridge and a few LED lights. It happened a couple times last night, then ran fine all night and day until about 10 pm tonight. Now it has done it probably 5 times tonight . I turned ac off and let sit for 15 minutes but that didn’t fix the problem. Each time I reset the breaker it takes less time to trip. AC ran fine the last time we camped a couple months ago but that was on shore power. Please help!

[MrMark52]

Chances are some of the wiring is failing in the A/C unit. Or a failing component. Not unusual.

Turn the power off, go up on the roof with a slotted and Phillips screwdrivers and 1/4” and 5/16” nut drivers.
Remove shroud.
Locate and open the electrical box that has the wiring from the fan motor and compressor running into it. Look for discolored wiring, particularly where the ends have crimped terminations. Make sure all connections are tight and have some “pull” to them.
If all looks good - identify the metallic capacitor(s) which are the run capacitors, and the PTC start device which will be a smaller, usually black device with 2 wires that is usually connected to the run capacitor for the compressor.
Once you’ve identified all the components (take pictures of their markings), close the unit back up, climb off roof.
Go inside, access the wiring compartment inside the ceiling bezel behind the filter. Make certain all wired connections there show no signs of overheating. Close it back up.

Access the breaker panel. Carefully, using a voltmeter - probe the output of the 20 amp breaker. While probing and watching the meter, have someone turn the A/C on. Note what voltage the meter reads as the A/C unit tries to start. If it drops below or is at 106-108, you either have too much load on the generator or the generator is failing.

If you have an amp-probe, you can make some additional measurements that would help to zoom in on the exact issue.

While you on the roof checking the unit out and the power off, take the water hose up and wash out the condenser. Wash it in the reverse direction that air is drawn over it. You can not access the evaporator for cleaning without further dis-assembly (although for the age of your unit, typically no real need to).

[twinboat]

I would think that the A/C coils are icing up at night.

Pull down the inside cover and see if the evaporator coils are covered with dust, limiting air flow. You may see frost on the coils right after it shuts down.

Also check for the thermostat probe is inserted in the center of the coil. It's designed to shut down the compressor before freeze up.

[sibe]

As mentioned icing up..is possble.

During the day in heat the compressor I bet never cycles .. at nite the compressor cycles as temps may be lower,, the cycling is hammering the breaker with a high load..

Breaker is weak or AC is drawing too much load.. A soft start may help or even a hard start.. Loose wire is possible but doubt it..

[Medicrn82]

Originally Posted by MrMark52

Chances are some of the wiring is failing in the A/C unit. Or a failing component. Not unusual.

Turn the power off, go up on the roof with a slotted and Phillips screwdrivers and 1/4” and 5/16” nut drivers.
Remove shroud.
Locate and open the electrical box that has the wiring from the fan motor and compressor running into it. Look for discolored wiring, particularly where the ends have crimped terminations. Make sure all connections are tight and have some “pull” to them.
If all looks good - identify the metallic capacitor(s) which are the run capacitors, and the PTC start device which will be a smaller, usually black device with 2 wires that is usually connected to the run capacitor for the compressor.
Once you’ve identified all the components (take pictures of their markings), close the unit back up, climb off roof.
Go inside, access the wiring compartment inside the ceiling bezel behind the filter. Make certain all wired connections there show no signs of overheating. Close it back up.

Access the breaker panel. Carefully, using a voltmeter - probe the output of the 20 amp breaker. While probing and watching the meter, have someone turn the A/C on. Note what voltage the meter reads as the A/C unit tries to start. If it drops below or is at 106-108, you either have too much load on the generator or the generator is failing.

If you have an amp-probe, you can make some additional measurements that would help to zoom in on the exact issue.

While you on the roof checking the unit out and the power off, take the water hose up and wash out the condenser. Wash it in the reverse direction that air is drawn over it. You can not access the evaporator for cleaning without further dis-assembly (although for the age of your unit, typically no real need to).

Thank you, this is very helpful, and I appreciate you taking the time to type all that out. We are only at this place for a few days so we don’t have a ladder with us, but I’ll definitely try to find someone who does. I can check the inside and also the volts. There is no water hookup here either so washing will have to wait until we get home. :( I’m just a girl who doesn’t know much about anything electrical or mechanical but I’m trying to learn as I go.

[Medicrn82]

Originally Posted by sibe

As mentioned icing up..is possble.

During the day in heat the compressor I bet never cycles .. at nite the compressor cycles as temps may be lower,, the cycling is hammering the breaker with a high load..

Breaker is weak or AC is drawing too much load.. A soft start may help or even a hard start.. Loose wire is possible but doubt it..

I let it sit all night and tried to start it again this morning. It flipped after only a couple of minutes, so I don’t think freezing up is the issue. I would guess maybe a bad breaker but I’m definitely not an electrician so it makes me nervous to think about trying to change it. Thank you for your reply.

[Medicrn82]

Originally Posted by twinboat

I would think that the A/C coils are icing up at night.

Pull down the inside cover and see if the evaporator coils are covered with dust, limiting air flow. You may see frost on the coils right after it shuts down.

Also check for the thermostat probe is inserted in the center of the coil. It's designed to shut down the compressor before freeze up.

I let it sit all night and tried to start it again this morning. It tripped after only a couple of minutes so I don’t think freezing up is the issue. We are only here for a couple of days so we didn’t bring a ladder but I’ll try to find someone who has one to climb up on the roof and check things out. Thank you for your reply.

[Jon_C]

As a test you could swap the breaker for another one same rating in your box if you have 2 same rating. If it still trips id suspect either compressor or possibly starting capacitor going bad causing to pull too many amps on compressor start. May be a good time to install a soft start.

If your genny voltage is lower than shore power volts that will also cause more amps at startup, id check that as well.

And if your genny is inverter style and has an eco throttle, turn that off, it causes low voltage when a heavy load starts until the genny can recover this causes more amps on startup.

[sshephard1]

I’m not sure if things worked as expected in previous trips. If so, my comments may be irrelevant. Nevertheless, I found that my 2000 watt generator (with a soft start I installed on the AC unit) tripped the fuse most of the time- even with other breakers turned off. I was using the 30’ shore power cord when this happened. I bought a 10’ shore power cord and haven’t had any problems since. The quality of the cord and the length of the run can cause issues. Good luck in solving your problem.

[Medicrn82]

Originally Posted by Jon_C

As a test you could swap the breaker for another one same rating in your box if you have 2 same rating. If it still trips id suspect either compressor or possibly starting capacitor going bad causing to pull too many amps on compressor start. May be a good time to install a soft start.

If your genny voltage is lower than shore power volts that will also cause more amps at startup, id check that as well.

And if your genny is inverter style and has an eco throttle, turn that off, it causes low voltage when a heavy load starts until the genny can recover this causes more amps on startup.

Update: climbed on the roof, no burned appearing wires, nothing was frozen up or dirty. Pulled the circuit breaker in the camper, nothing appeared burned there either. Replaced the circuit breaker and the new one ran for about 20 minutes then tripped. We did get condensation running down the RV while it was working. Now running just the fan without ac to see what that does. It is a normal generator, not inverter type.

[Medicrn82]

Originally Posted by sshephard1

I’m not sure if things worked as expected in previous trips. If so, my comments may be irrelevant. Nevertheless, I found that my 2000 watt generator (with a soft start I installed on the AC unit) tripped the fuse most of the time- even with other breakers turned off. I was using the 30’ shore power cord when this happened. I bought a 10’ shore power cord and haven’t had any problems since. The quality of the cord and the length of the run can cause issues. Good luck in solving your problem.

Thank you, I do know that longer cords cause more issues. We unfortunately only have the one shore power cord.

[Medicrn82]

Update: climbed on the roof, no burned appearing wires, nothing was frozen up or dirty. Pulled the circuit breaker in the camper, nothing appeared burned there either. Replaced the circuit breaker and the new one ran for about 20 minutes then tripped. We did get condensation running down the RV while it was working. Now running just the fan without ac to see what that does.

[hclarkx]

Sure does sound more and more like the generator is not doing its job. Testing on shore power may answer that question.

From the wording, I'd guess that the breaker trips seconds or minutes after the A/C has started. If so, it's not the start-up current that is the problem (beyond maybe pre-heating the circuit breaker). Or the generator voltage drop during start-up. I.e., the problem is during "steady state" operation (after start-up). Checking the voltage at the panel with the generator running, before, during start-up, and following start-up right up to the time the breaker trips would tell you a lot. A usable voltmeter is (or used to be) $5 at Harbor Freight.

BTW, low generator voltage will not cause higher start-up current. Under locked rotor conditions (or the compressor motor still at lower RPM as it spins up) the load on the generator is a "constant impedance" and so ohm's law applies. Lower voltage means lower current. Once the motor is running at speed, the opposite occurs (lower voltage means higher current).

[VanK]

I suggest you hire an electrician to check to current (AMPs) and power (Volts) to the breaker under different conditions. HClarkX is mistaken in his claim that lower voltage equals lower current. It's actually an inverse relationship. The electrician will have a multimeter with a hold function to measure the highest AMPs drawn during start-up. The breaker trips on heat or over-current. Breakers are also only rated to trip seven times in their life. I hope this helps. If you are in or near Charleston SC I'll be glad to help at no charge since I am a fellow traveler and retired electrician.