Roof AC tripping shore power/generator

[caymann]

I was exercising the roof AC in heat pump mode (i also tried AC mode) and the shore power OR the generator (10kW) was tripping its breaker. I narrowed down the culprit to the bedroom roof heat pump/AC. When i shut it off (or just ran the fan in it) the generator was happy.

So i went up to the roof and took out the cover. Everything looking neat and clean on the coils. I sprayed some AC cleaner and ran the system again resulting in tripping.

The tripping really happens after running for 20mins or so.

Inside the bedroom, the roof AC also sounds rather loud and wife wants it off when sleeping.

Any AC gurus out there to explain this (other than your compressor is dying ...) and what i can try/do to fix this?

This is a Duotherm 13.5k BTU Heat Pump

thanks
jim

[RJay]

Jim,
The bedroom roof A/C always seems to be louder because of the smaller confined space in the bedroom area. Your problem is sometimes caused by a low supply voltage but where your problem occurs on both shore power and generator and only after a period of time it seems the problem is with the A/C itself. Start by measuring the voltage at the A/C and make sure everything turns freely.

[Andy Jackson]

Like RJay said a good start would be to check the voltage at the A/C. A spike in voltage usually means you're low on refrigerant which can cause the compressor to short cycle and trip your breakers.

If your up for it, you can also try and check the start capacitors but I would really recommend having a certified technician do this for you. If you remove the A/C cover you should see a metal access cover located toward the front of the A/C. Remove this panel and visually inspect the black start capacitors but be very careful not to touch anything once you have the panel removed, especially the capacitors, or you will get shocked. Visually check the capacitors to ensure that they are not melted in any way.

Andy Jackson

[caymann]

Voltage measurement: Should i be looking for the voltage or current draw?
If voltage drop - between what points?
If current draw - on which wire (i think the white one but not sure)?

The black start capacitor looks fine - visually.
Should i be measuring any voltage there (after discharging the capacitor of course by shorting the leads with a screw driver)?

[Andy Jackson]

Check the amperage draw at the black wire at compressor. If its between 23-27amps while running (not startup) the compressor is bad. You can also look for oiling or chalking residue on the coils which means you have a refrigerant leak in the system. Dometic also has very good tech support. You'll probably be on hold for awhile but they can walk you the process and possibly add a few other points to check out.

Good Luck and lets hope it's not the compressor

[caymann]

I think you meant the white wire - 10Amps (70F outside)
Voltage across white and black wire of compressor 118V
I measured this 10mins after the AC mode compressor kicked in.

Black capacitor (start cap) looks good
PTCR looks good
White capacitor (run cap) looks good

Could the white capacitor be bad as it only trips in the long run