Coleman Mach Airxcel problem

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fisherbrent

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Dec 10, 2019
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We have a 2019 Pinecrest 305 RLP 5th wheel by Vanleigh with 2 Coleman Mach AC units running on 50 amps.  Most of the time both units operate fine.  Sometimes the units will run for less than a minute then shutdown.  Most technicians state that is a problem with the pedestal at the site and not anything wrong with the trailer or AC units.  Both units--running together or separately--exhibit the same behavior.  When they do shut down, one of the GFCI outlets also gets tripped. 

No breakers are tripped -- in the trailer or at the pedestal -- but one GFCI does trip at the same time.  This would seem to suggest that there is some power issue that causes the GFCI and AC units to trip.  Turning off the breaker for the circuit that has the GFCI does not stop the AC units from shutting down.  When turning off ALL breakers except for one 20-amp breaker for one of the AC units, that AC unit still shuts down.

Running the AC fan only does not cause it to shut down.

Even though there is at least 120 volts on each leg, the current under load may be inadequate to run the AC compressor(s).

Has anyone seen similar behavior?
Again, many parks and my home pedestal does not cause this problem.  So, it would seem that there is nothing wrong with the units or trailer wiring.  Any work arounds? 
Is there someway to test the pedestal (since it needs to be under load for current and not just the voltage potential difference)?
Any other suggestions?
 
 
That's really mysterious!  If it only happens with some power pedestals, it has to be related somehow to the power source, yet I cannot explain anyway that would cause a GFCI trip inside the trailer.  That has to be a ground fault in that circuit, i.e. a short from hot to ground or neutral to ground.  The fact that it only fails on certain pedestals is crucial to the diagnosis, so we will have to trust that you've carefully and fully verified that.

Do you have a power line monitor & surge protector on the shore cord?  Like a Surge Guard or Progressive Industries EMS?  They are a bit pricey but "priceless" if you run into a faulty power source and would help solve this problem as well, even if just by eliminating some possible but obscure issues (e.g. bad voltage or frequency).
 
Thanks, Gary
This problem has only happened at a few parks but some of these have other 50-amp RVs that apparently don?t have a problem but most places we?ve stayed has not been a problem...
Yes, I have. Progressive Industries EMS to protect the trailer but have also tried bypassing just in case it was the problem.
A mystery for sure!
 
So the Progressive EMS doesn't report a fault when this happens? That would seem to rule out a voltage fluctuation as the cause.

The Ground Fault suggests there is a backfeed into that circuit when the a/c drops out, but that's an effect rather than the cause. It does, though, imply there is some sort of wiring issue in the RV, cause that shouldn't happen either.  Someone with pretty good electrical wiring skills could check the neutral and ground wiring in the load center and maybe see if there is a neutral-ground bond that shouldn't be or maybe some other wiring mistake. The assembly line workers aren't electrical pros - just following instructions.
 
Gary,
That is correct, the EMS reports no errors.

Now for the good news!

The insulated 110-volt wire was found to be touching the metal mount frame. It appears that this wire may have rubbed the edge of this mount and then was close enough to arc (intermittently). This wire also had a sharp twisted angle that MIGHT have contributed. And, finally, the AC control board had the neutral and ground wires reversed.

Not sure if it was any one of these or the combination, but it does also explain why the GFCI was also tripping.

Thanks for your help and maybe this will help others.

-Brent
 
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