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Topic: Roof Air Trips Breaker (Read 672 times) previous topic - next topic

Roof Air Trips Breaker

Our front roof AC unit has started to trip the circuit breaker that is mounted under the bed. It was fine last fall, but as soon as we turned it on this spring it began tripping the breaker. It will run for about 5-10 minutes before it trips. I checked the current draw on my Hughes Power Watchdog, and it shows 35 Amps on the leg with the front AC. With the rear AC running, the other leg only shows 15 Amps. I have cleaned the coils and visually checked the unit—no sign of leaking or bulging capacitor. Does anyone have any suggestions besides a trip to Nacogdoches?

David and Kathy Bennett
2004 U270 "Harvey"
Dave and Kathy Bennett
2004 U270
Build #6253
1600W Solar
700 AH Battle Born Lithium
2015 Jeep Wrangler

No matter what happens, remember you always get the trip out of it.

Re: Roof Air Trips Breaker

Reply #1 –
I'm not a electrical expert in any sense of the word, but obviously something in the front unit is drawing too much current.

To troubleshoot this type of problem, a clamp-on ammeter is very handy.  The EXTECH brand is often mentioned favorably on this Forum:

EX655: 600A True RMS AC/DC Clamp Meter + NCV | Extech Instruments

It would be informative to measure the current going to the motors on both units while they are running.  If the front motor is getting "tired" it may show up as a high current draw.

If you can pinpoint the component that is causing the AC breaker to trip, then you can have a more informed discussion with any potential repair location about your options.

How far are you presently located from NAC?  Roof A/C units can be serviced by most any qualified repair facility.  We had both of our roof units replaced last year by the excellent crew at Nacogdoches Motorhome Service.  We were very pleased with their work.

New Air Conditioners
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Roof Air Trips Breaker

Reply #2 –
It is possible that the breaker is getting "tired" and these are nuisance trips.  Find a replacement breaker and replace the one that is tripping.  Get a couple to have in your spare parts collection.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Roof Air Trips Breaker

Reply #3 –
Quote from: Roger & Susan in Home2 –
It is possible that the breaker is getting "tired" and these are nuisance trips.  Find a replacement breaker and replace the one that is tripping.  Get a couple to have in your spare parts collection.

Could be, but not the root cause.  OP said front A/C drawing 35 amps, rear 15.  Depending on age of front A/C, not sure I would waste too much time fooling with it after determining that the fan motor was not the issue (the only economically reasonable replacement part).  Easy to determine-- turn on fan only and see how many amps it pulls.

Said another way, if the compressor is drawing many times its designed load, replace the A/C.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Roof Air Trips Breaker

Reply #4 –
As Brett says. Check to see if both fan is running and you hear compressor running. If fan is not working it will be in lock rotor and cause the high amps. Could be something made a nest in there over the winter and not letting the fan turn.  Other problem could be a short in the winding on the compressor. If that is the case then time for new unit. With unit pulling 35 amps the breaker should trip since they should trip around 20 amps.
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Roof Air Trips Breaker

Reply #5 –
FYI....I was having this issue going down the road with the front one tripping the breaker, but front air worked fine when parked.
As Rodger said, may be breaker. I changed mine out, no more issue's. Found one at Ace hardware.
If it's not that, probably the compressor is going bad. Not repairable. Like Brett said, change the whole unit out.
But realize there are older and newer gen boards in the units. So you may be changing out more then just the unit. At the minimum, dip switches in new unit will need to be set in the correct order.
Chris
Chris and Tammy White  CDA Idaho
Previous owners 1997 U295 36' 3126 Cat 300 HP Build # 4998
Former Foretravel tech & RVIA certified tech
Former owner Custom Satellite home/RV satellites 
Former owner Vans LTD  van conversions
Unemployed, panhandler, drag racer NHRA #6348

Re: Roof Air Trips Breaker

Reply #6 –
Thanks for all the replies. After Chuck mentioned testing with an ammeter, I remembered I have one from many years ago when I was in an entirely different line of work ( I teach school now; I owned car washes then). I found it in my garage, and the compressor tested at 25 Amps. I think it's time to research new AC units. Does anyone have any recommendations?

Thanks again for all your help,

David and Kathy Bennett
2004 U270 "Harvey"
Dave and Kathy Bennett
2004 U270
Build #6253
1600W Solar
700 AH Battle Born Lithium
2015 Jeep Wrangler

No matter what happens, remember you always get the trip out of it.

Re: Roof Air Trips Breaker

Reply #7 –
David,
With this COVID-19 issue we are all facing and no where to go, we have have been keeping ourselves busy working on the motorhome.  One item on the list is to replace both AC units.  After long research on different units and looking at what individuals have installed.  We chose to keep it simple and stick with Dometic.  We ordered 2 Penguin II High Capacity (15K BTU) units with heat pumps, 2 ducted returns and a new thermostat through PPL.  After talking with Dometic technical support, everything will connect using all of the existing wiring, including the bedroom sensor.  The only issue is we ordered them 2 weeks ago and we still have not received anything.  After talking with PPL we learned that Dometic is in Indiana and they have been on shut down due to their state restrictions with the virus.  They said they are hoping to get in April 4 and handle any orders.  We are hoping this doesn't change and we can get our order.  Meanwhile were are working on the roof removing satellite dish, old AC units and repairing any holes from old equipment, cleaning and sealing the roof.

John M.
John & Carm Morales

"We travel not to go anywhere, but to just go.  We travel for travel's sake.  Our great desire is to move."

Re: Roof Air Trips Breaker

Reply #8 –
Hi John,

What was the deciding factor in going with the Dometic Penguin II? I am still trying to decide what to go with.

Dave Bennett
Dave and Kathy Bennett
2004 U270
Build #6253
1600W Solar
700 AH Battle Born Lithium
2015 Jeep Wrangler

No matter what happens, remember you always get the trip out of it.

Re: Roof Air Trips Breaker

Reply #9 –
One other thing to check, before writing off the unit, is the motor capacitor. It's located in the small curbside compartment of the unit. A bad cap will cause high current draw/breaker tripping.
Greg & Cathy
2000 U320 4010 DGFE Build #5650
Had: 1999 Tradewinds 7370

Re: Roof Air Trips Breaker

Reply #10 –
BUT, a bad capacitor will show high (even very high) amp draw on START UP.  High amp draw after 10+ minutes should not be related to a capacitor.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Roof Air Trips Breaker

Reply #11 –
Quote from: wolfe10 –
BUT, a bad capacitor will show high (even very high) amp draw on START UP.  High amp draw after 10+ minutes should not be related to a capacitor.
Brett, I agree, ...if the start cap has failed. These units have a start and run cap for the compressor. The run capacitor is a 3 terminal unit: common, fan, compressor, (dual unit) that is for running of both motors. The compressor start cap is a 2 terminal unit. If the compressor side of the 3 terminal cap has failed, that could cause the high compressor current after startup. I'm not one for blindly swapping parts but an easy way to verify the capacitor would be to remove the 3 terminal cap from the working unit and put it in the failed unit. If it works, just buy a new cap.

Dave, If you decide to give this a try, don't forget to shut off the breakers for both units before playing with the wires.  :o

Greg
Greg & Cathy
2000 U320 4010 DGFE Build #5650
Had: 1999 Tradewinds 7370
 

Re: Roof Air Trips Breaker

Reply #12 –
If the capacitor didnt fail regardless of turning off the breakers... IT WILL STILL HAVE POWER IN THE CAPACITOR.. it will need discharged or you will get a massive jolt