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Isaac-1 · 05-20-2022, 07:44 PM

Our 20 year old Dometic DuoTherm 15K BTU heat pump has started tripping the 20 amp breaker in our motorhome's breaker panel. So far it has done this twice in the last week at two different locations, tripping during heat of the day. Other than this detail it seems to still be running ok, and I would like to put off replacing it a little longer if possible given the current supply chain shortages, etc. My thoughts are to take the shotgun approach when we get home from our current trip, replace the breaker, hose out the coils, and replace the capacitors, as I have done nothing to it other than cleaning the coils in the nearly 6 years we have owned this coach.

Any thoughts on anything else worth considering?

Skibane · 05-20-2022, 07:52 PM

It's also possible that your 20 amp circuit breaker is getting "weak" - i.e., no longer capable of carrying anywhere near 20 amps without tripping.

They sometimes do that.

If you're somewhat handy, you can try substituting another of your RV's 20 amp breakers for that one. If the swapped breaker doesn't trip when powering your air conditioner, you know that the old one is starting to go bad.

Or, you can just buy and install a replacement breaker to see if that fixes it. Typically, they aren't very expensive.

twinboat · 05-20-2022, 08:06 PM

I would start with cleaning the coils, it worked for my 15 year old unit.

bigb56 · 05-20-2022, 08:10 PM

Do you know if it trips at startup or after it has been running for awhile? Monitoring the amp draw would help point you in the right direction.

Isaac-1 · 05-20-2022, 08:53 PM

Quote:

Originally Posted by bigb56

Do you know if it trips at startup or after it has been running for awhile? Monitoring the amp draw would help point you in the right direction.

I don't know for sure, but suspect it happens while it has been running for a while (hours).

Before going too far on it I will probably put a clamp meter on it and check for max amps.

DFord · 05-21-2022, 03:14 PM

What you're thinking about doing should eliminate many of the common problems but another thing that might be a problem is the fan motor. Be sure it's turning freely. It could stand some oil after all the years. Make sure it's not slowing down. Many of those motors are "sealed" and getting oil to the bearings is a problem.

hypoxia · 05-22-2022, 07:37 AM

You are getting a lot of good suggestions. One more is if the breaker panel is on the west wall when it has been tripping? They are tripped by heat & I always open the cover to the breaker box on hot days when parked with the box on the west side.

Monaco installed an A/C vent in the breaker panel compartment which is at the front of the bus to control the heat on the breakers but sometimes the front & middle A/C units are not running while the rear A/C is so no air is blowing into that compartment and the rear breaker trips on those 100+ degree days when it is west facing.

hypoxia · 05-22-2022, 07:54 AM

Quote:

Originally Posted by DFord

What you're thinking about doing should eliminate many of the common problems but another thing that might be a problem is the fan motor. Be sure it's turning freely. It could stand some oil after all the years. Make sure it's not slowing down. Many of those motors are "sealed" and getting oil to the bearings is a problem.

Yesterday my rear A/C kept quitting as I was troubleshooting it. The end result was the fan run capacitor was checking good 2 times at 15 mfd but was going bad causing the fan to change speeds which caused the compressor pressures to rise. I replaced that capacitor (45/15 mfd) on principal which solved the problem.

Once finished I checked the capacitor while wiggling the terminal and bumping it lightly & then it finally showed 0 mfd and never changed value again. For a while I thought the fan motor was the problem as it was running hot. I have a spare fan motor and decided to install it but decided to replace the capacitor before going to all of that work. Lucky decision.

Isaac-1 · 05-22-2022, 08:19 AM

That just goes to show that even when things seem to test good, they may not be. It is all somewhat moot though at the moment, we are at a full hookup campground in NW Louisiana right now, and the power has been out for the last 5 hours. Thankfully the temperature is about 70 degrees outside with light rain, so no need to crank the generator to run the air conditioner yet.

jacwjames · 05-22-2022, 08:21 AM

Back in 2015 my front AC started to get louder and would occasionally trip the breaker. I started test and noticed that at start up, watching my EMS panel, it would pull really high amps at startup.

I removed the cover on the AC and tried to spin the motor, it was very hard to spin by hand, the motor was almost locked up. I also noticed that the motor itself would move, the rubber mounts were shot and would actually let the out fan blade hit the sheet metal.
I was able to find a replacement motor kit which included the rubber mounts. Cost was ~$125.
Removed the front fan blade in place and left is sitting under the sheet metal, this was easier then removing all the sheet metal enclosing it. Had to completely remove the motor and metal shroud to be able to get it to my workbench to take the rear blade off.

Got the new motor and replaced and all was good. So I would check the motor and rubber mounts.

Fast forward to last year, my wife took the coach for a trip and commented that the rear AC had made a bad noise but then quieted down. So I took the cover off the rear and found the rubber mounts shot but the motor seemed to be fine. But I decided to replace the motor, problem was I couldn't find one, it was obsolete. One of my fan blades looked pretty bad and tried to find one, also not available.

Hmmmm, after thinking about it I decided to just go ahead and replace both AC's , Yup I did it. Bought two new high capacity 15K btu AC/heat pump and new thermostat.

hypoxia · 05-22-2022, 10:02 AM

Anyone considering replacement A/C units needs to consider that new refrigerants will be in place by the end of this year. R410 will be replaced by R454B or whichever refrigerant that Dometic and other manufacturers choose. I still have 11 heat pumps with R22 which have been relatively trouble free compared the R410 units which have been problematic probably due to the extremely high discharge pressures. R454B is slightly less pressure than R410 which may slightly improve reliability.

DFord · 05-23-2022, 08:17 PM

The date R454B will replace R410 is still up in the air. It may not happen until Jan 1st 2025. No sense in waiting. You're not going to gain anything. If you take care of your a/c, it should last many years without failing.

My little church is looking for bids to replace their air conditioner for the sanctuary after only 47 years. Not because they've failed but because the casings have rusted out and condensate is coming out everywhere but the drain.