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Phil, Mechanical Engineer
Category: HVAC
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Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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My mach 3 rv ac keeps tripping my 10000 watt generator

Customer Question

My Coleman mach 3 rv ac keeps tripping my 10000 watt generator breaker. How do i fix this?
Submitted: 2 months ago.
Category: HVAC
Customer: replied 2 months ago.
The generator is a 10000 watt DuoMax generator. This happens on the 220 plugin on the generator. The ac unit is a Coleman Mach 3 ac unit. I ran 12/2 AWG wiring from the AC, connecting blk/blk, green/copper, why/wht. Then in the breaker box I connect the black to a 15 amp breaker, the bare copper to the ground bar and the white to the neutral bar. The cabling from the breaker box inside to the connector box outside uses 10/3 gauge copper wire. Black to the first hot post in the breaker box, red to the second hot post in the. Reader box, green to the ground bar, and white to the neutral bar. There are other circuits connected in the breaker box, however even when I remove all other circuits from the interior breaker box the ac still causes the generator circuit breaker 50 amps to trip. I need help determine what is causing this problem. Can you please assist me?
Expert:  airheatman replied 2 months ago.

Sounds like the issue is most likely the unit not your wiring.

Does it trip immediately when you turn ac on?

Customer: replied 2 months ago.
After cranking up the generator and switching the generator breaker to on, I think turn the AC to fan for about a minute then over to low or high cool. The AC will stay on for about 4 minutes then you can here the generator rev up then eventually the 50 AMP circuit breaker on the generator throws. If I flip the circuit breaker back, the ac will stay on for about 1 minute at most.
Expert:  airheatman replied 2 months ago.

First step in troubleshooting is going to be to verify the amp draw on compressor when it trips.Do you have a clamp on meter?

Customer: replied 2 months ago.
Not at this time but I can get one. Where on the Coleman Mach 3 would I find the compressor. Will I need to take the cover off of the top unit or should I be able to get to it from the interior?
Expert:  airheatman replied 2 months ago.

You will need to remove the cover.Locate the 3 wires going to compressor and clamp one single wire at a time.Without the meter you can check a couple of things visually. Make sure the capacitor does not look swollen and make sure all three wires are secure on the compressor

Customer: replied 2 months ago.
I will get the meter this afternoon. What amperage should I be looking for? The AC unit should be drawing 14.9 AMPs are full load. Also I read up that it will draw 50.4 AMPs at rotor lock up. (I dont quite know what rotor lock up means)More importantly will the wires be color coordinated to assist me with knowing which in hot and which is ground?
Expert:  airheatman replied 2 months ago.

The compressor wires we want to amp are none ground.One is Common One s Run and one is start. The locked rotor indicates that the compressor is locked up, but often a weak or dead capacitor will prevent starting and cause the locked rotor amperage

Expert:  airheatman replied 2 months ago.

As a rule of thumb the amp draw should run 70 to 80 per cent of RLA but never exceed the 14.9

Customer: replied 2 months ago.
Am I assuming correctly that the amp draw that I measure will help determining if the capacitor is weak or dead?
Expert:  airheatman replied 2 months ago.

If amp draw is high, next step s to check capacitance on the capacitor.If amp draw is normal up until it trips, that would indicate a short ether in compressor or compressor wiring. So then we would remove each wire to compressor and check each of the three terminals to ground .If we have continuity between any terminal and a known ground like a cabinet bolt,compressor is bad.

Customer: replied 2 months ago.
Okay I will check all this afternoon and respond back.
Expert:  airheatman replied 2 months ago.

WE will go from there

Customer: replied 2 months ago.
ok Thanks
Expert:  airheatman replied 2 months ago.

Look forward to hearing back