Coleman Mach 8330 Series Rooftop AC Trips Breaker

[talotto]

Helping a friend troubleshoot his 5th wheel: Before we replace the whole AC unit, I'm hoping someone has an idea I haven't tried. After running for a while (15-20 minutes typically - sommetimes for hours) the 20A breaker will trip. Up until that time the unit is working correctly, blowing cold air, not making any unusual noise, etc. Things I've tried: New Thermostat, new start and run capacitors (fan and compressor), added a hard start unit to the compressor, new control board, checked/verified all connections are correct, not shorted nor grounded, cleaned the coils and new filter, new 20A breaker in the breaker panel, removing the weather cover. Does anybody have any suggestions I haven't tried? By the way, this is in central Texas, so it has been hot - but the companion unit is working fine.

[j-d]

Chris Bryant weighed in above, and his suggestion to Clean It is always good! He has a blog post on this but I'm having trouble finding and linking it.

Chris also helped me (like so many others! Bless You, Chris!) when he said what basically comes down to this:

The Plastic Shroud should be baffled at the edges of the Condenser Coil (the one visible at the back of the A/C, where the Outdoor Fan Blade is). Baffled in a way that air being exhausted out the sides of the Shroud isn't also being pulled INTO the Condenser Coil from INSIDE the shroud. There should be foam strips in there, shaped to close the air path around the edges of the Condenser Coil. If yours are gone, the A/C will overheat, and draw more Amps.

[talotto]

UPDATE: Problem fixed! Thank you to all who replied. Carefully checked volts and amps all along the path from pedistal through cord (no extension cord, only the trailer umbilical), transfer switch, breaker panel to the AC unit. No unusual voltage drops noted (about a volt total end to end). Re-cleaned the condenser coils, straightened many fins that had been dented. Amps dropped from 18-19 running (cooler day than normal) down to around 14 and the unit has been running as it should for the past several days. Thanks again for all the expertise and professional advice!

[Captain_Happy]

Without throwing more parts at the problem I get an amp meter, and a volt meter(separate)units. Turn on the A/C unit and monitor the amps & volts are doing. I'm thinking maybe your having a voltage drop problem which is causing the breaker to trip. Remember, when voltage goes down, amps go up. And also check the voltage at the source. And remember when the compressor starts the amps can be at least 8 to 10 times the running amps for a split second. Which an average amp meter will be able to read. Just me 2 cents worth.

[greenrvgreen]

What everyone else said, PLUS:


After careful ammeter monitoring of how much joice is tripping the new 20A breaker, and the amps are not out of line, it is THEORETICALLY possible that your BREAKER is overheating.

Electricians (I'm not one) have mentioned this possibility to me in the past because I really like to pack the breakers in tightly, including doubles. Never had any trouble, but I've never visited Texas.

FWIW!

[ScottG]

If the extension cord is coiled up it can cause excessive current drain.

[kerrlakeRoo]

Shut down everything in the unit except the AC units, If the problem stops, turn on one breaker, wait a half hour then turn on another,,,,,,, You'll find the gremlin.

[Chris_Bryant]

Clean the condenser coils again- spray with a ph neutral degreaser (they recommend Formula 09), let it soak, and hose it off.

[Joe417]

Another thing that will pull a little more current is the fan motor. Even thou it turns without noise they sometimes get dry bushings and will eventually fail.

As 2oldman said, if you're dropping voltage through a extension cord, either remove it or get a larger one. Verify what voltage is at the post and then at the AC.

Have you checked run current to see what it is normally running at, when it's running "normally"?

There is a device to delay the unit from trying to start the compressor for a couple of minutes after power is applied or if the compressor cuts off. I would figure that would be part of the control board you've already replaced. It may not be. The item on some ACs is a separate device, one company that used to make them was Klixon.

[2oldman]

Get rid of the extension cord? Sounds like you have a voltage problem.