Rooftop AC Tripping Breaker... Sometimes

[MSU_Dog_Hauler]

I have a 2001 Monaco Knight with 2 Dometic Duo-Therm AC units. The Rear air works fine and the front has started tripping the breaker. I have cleaned both sets of coils, replaced both capacitors, replaced the motor and installed a new breaker. The unit will run and cool fine all night, but when the sun comes up and the temp starts to rise above 85 or so, the breaker will trip. I can wait an hour or so, and re-set the breaker and it will start up again, but only run less than a minute before it trips it again. If I wait till the sun goes down and the temp drops it will not trip until the next morning. The system has never been tapped, so I don't know about the freon level. Anybody have a similar experience I can learn from? Thanks in advance for your help.

[wa8yxm]

Mine was tripping on every compressor restart. I put a soft start kit on it and not it tripps... Sometimes. Often at like 3 or 4 amp when it's really quite cool

Will need to replace it .. Soon

[garry1p]

One thing to check before throwing in the towel and buying a new unit. Possible the run capacitor on the fan is bad letting the fan slow down just enough to allow the coils to run hotter than normal.

[dougrainer]

MSU Dog Hauler wrote:
Thanks for the feedback everyone.
I'm sure the coils are as clean as they can be. They weren't too bad to start with, but I used a shop vac with a brush attachment to get the few items that were large enough to see. I then soaked them with a foaming coil cleaner and finished them off with a good rinse with the water hose. I did this with both sets of coils.
I don't think it is the supplied voltage either. I have had the same issue at 2 different RV parks, using the generator, and plugged up at my home.
I'll check the amp draw using an extension cord. That should tell me something. I don't think the coach has the amp draw on the EMS, but I know where I can borrow a meter.

50 amp EMS will NOT show amp draw when connected to 50 amp service. To test, you either connect to 30 amp or run the Genset. On Genset you will have total amp draw. Doug

[oldave]

MSU Dog Hauler wrote:
Thanks for the feedback everyone.
I'm sure the coils are as clean as they can be. They weren't too bad to start with, but I used a shop vac with a brush attachment to get the few items that were large enough to see. I then soaked them with a foaming coil cleaner and finished them off with a good rinse with the water hose. I did this with both sets of coils.
I don't think it is the supplied voltage either. I have had the same issue at 2 different RV parks, using the generator, and plugged up at my home.
I'll check the amp draw using an extension cord. That should tell me something. I don't think the coach has the amp draw on the EMS, but I know where I can borrow a meter.

With the additional info you are more than likely looking at
replacing the A/C . You know its drawing excessive amps
because the new breaker trips .
You have already gotten more yrs of use than most .
Be sure the new unit will communicate with the thermostat
and the other A/C or go ahead and replace both units and
thermostat .
That's what I did , 2 new A/Cs and thermostat .
I didn't really want to spend the money but DW said I ain't
going if its hot in there . Glad I did now .
Ray

[MSU_Dog_Hauler]

Thanks for the feedback everyone.
I'm sure the coils are as clean as they can be. They weren't too bad to start with, but I used a shop vac with a brush attachment to get the few items that were large enough to see. I then soaked them with a foaming coil cleaner and finished them off with a good rinse with the water hose. I did this with both sets of coils.
I don't think it is the supplied voltage either. I have had the same issue at 2 different RV parks, using the generator, and plugged up at my home.
I'll check the amp draw using an extension cord. That should tell me something. I don't think the coach has the amp draw on the EMS, but I know where I can borrow a meter.

[Artum_Snowbird]

One thing to check and be sure of is the electrical supply both to the A/C and back on the neutral wires. It is a heavy load on the connections, and having a loose screw holding down wires is a real possibility when things don't seem right.

A very useful tool is a laser dot thermometer. Point the dot on the screw terminals and if you see heat buildup at any point, it is likely a loose connection.

Definitely get a voltmeter and put it on the supply terminals on the shore power. If your connections are good, you should have the same, or very close to the same voltage right at the A/C. If not, then you are losing some along the wiring. Continue checking with your meter on the panel board.

Sometimes the way to prove good solid wiring is to have an extension cord set up. Plug into the shore power, and at the other end, connect to your A/C. If it keeps running then, but won't keep running through the rigs wiring, this proves the A/C itself is good, but the wiring to or from and back to the neutral is suspect.

[oldave]

I fear ultimately Doug is going to be correct , bad compressor .

Before condemning it though I would give the condenser coils
on the roof a through cleaning again . Stuff can get imbedded and some
areas are hard to get at .

Also some A/Cs have a foam rubber strip under the plastic cover
that helps keep the air flowing through the coils , it needs to be
in place or some air can bypass the coils .

Do you know what the park voltage is ? Low voltage can cause problems .
This time of the year everyone is running their A/Cs full blast which
causes low voltage through out the park or probably the entire area .

Ray

[DFord]

You cleaned the coils but did you really get them clean? How's the air flow through the coil on the roof? If it's still blocked, the symptoms you describe make sense. The problem sounds related to heat build up on the condenser (outdoor) coil side. The heat isn't being rejected fast enough. Air flow through the outdoor coil is critical.

[dougrainer]

You have a bad compressor. Your symptoms point to that. To verify, you need a AMP draw of the compressor. Without special amp draw meter, you may be able to do a draw test. Not sure if 2001 Knights had the Intellitec EMS system that shows amp draw on the inside remote panel. If so, you can start the AC unit and watch the amp draw. You should have a baseline with other 120 appliances running. Watch the amp draw increase as the front AC starts up. The MAX increased amp draw caused by the AC should be 14 to 15 amps. Watch the amp draw in the heat. If the amps slowly increase above the 14 to 15 start up, then your compressor is bad as long as the Condensor coil is clean. If no EMS system, then you will have to get a Amp draw meter. Doug

[MSU_Dog_Hauler]

I already replaced the breaker. I did notice the compressor was hot to the touch, if that helps. I don't know if that is normal.

[rgatijnet1]

I assume that where you are parked the voltage is stable and not going up and down. Circuit breakers will wear out so you might try replacing the breaker that is tripping. Also at some electronic stores you can buy an aerosol can of spray coolant. With this you can spray individual components to see if cooling any of them solves your problem.