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Topic: Rear A/C Trips Shore Breaker on Shut Down (Read 389 times) previous topic - next topic

Rear A/C Trips Shore Breaker on Shut Down

I have a 2002 U320 - My front and rear A/C both work fine and the fans cycle on/off as would be expected.  On occasion when the rear A/C turns off it will trip the shore 50 Amp Breaker.

I have a surge protector from the breaker to my rig.  Is there something I can put in line to protect the shore breaker from tripping.

Any suggestions on what my be causing the power surge when the unit shuts down?  This happens about 40% of the time.  If I turn off the unit with the thermostat prior to it shutting off on its own the breaker does not trip.

Re: Rear A/C Trips Shore Breaker on Shut Down

Reply #1 –
Wow, that's a new one-- tripping a breaker when going from load to no load.

Has this happened on different 50 amp connections?
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: Rear A/C Trips Shore Breaker on Shut Down

Reply #2 –
I would  pull  the cover off and check the connections where the coach wire connects to the AC wiring. Also check the circuit board to see if something does not look right on it. Such as burn marks, capacitors that have split or swelled out. Check also the run and start capacitor to see if split or swelled.

I am going to say there is problem with the control circuit board.  Reason to say this is that is the common dominator between unit shutting off on it's own and being shut off by thermostat
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: Rear A/C Trips Shore Breaker on Shut Down

Reply #3 –
"If I turn off the unit with the thermostat prior to it shutting off on its own the breaker does not trip."
Wonder what would be the difference in manually turning it off to the set temperature achieved turning it off.
Future Foretravel Owners
2019 Jeep Cherokee Trailhawk
Retired USAF, Retired DOD Civ's
FAA A&P, Indust. Eng., Acft Depot Lvl. Maint.
Larry and Becky Rountree

Re: Rear A/C Trips Shore Breaker on Shut Down

Reply #4 –
I don't know why it is happening but when you turn the thermostat off the compressor shuts off before the fans do. When the air shuts off on its own they both shut down together.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Rear A/C Trips Shore Breaker on Shut Down

Reply #5 –
Likely campground pedestal 50-amp breaker is the problem. Nothing you can do, except ask for the breaker to be changed.

Re: Rear A/C Trips Shore Breaker on Shut Down

Reply #6 –
Quote from: Barry & Cindy –
Likely campground pedestal 50-amp breaker is the problem. Nothing you can do, except ask for the breaker to be changed.

Yup, that is why I asked if this was happening at more than one CG/pedestal.
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: Rear A/C Trips Shore Breaker on Shut Down

Reply #7 –
Are you certain the rear AC shutting off trips the circuit breaker or is the Breaker tripping and thus shutting off the AC simultaneously?
Just a thought. 
Justin & Cathy Byrd
1995 U280 "Old Faithful"
36' Build #4673
C8.3 Cummins
Allison MD3060R 6 speed - retarder
Powertech 10KW  4cyl Kubota

Re: Rear A/C Trips Shore Breaker on Shut Down

Reply #8 –
Quote from: wolfe10 –
Wow, that's a new one-- tripping a breaker when going from load to no load.

Has this happened on different 50 amp connections?

It just started last week and have been at the same location... will move to a new lot and check next week.

Matt Brown
2002 40' U320

Re: Rear A/C Trips Shore Breaker on Shut Down

Reply #9 –
Quote from: FourTravelers –
Are you certain the rear AC shutting off trips the circuit breaker or is the Breaker tripping and thus shutting off the AC simultaneously?
Just a thought. 
Definitely the unit shuts off and the breaker trips...  I have been testing it the last few days.

Matt Brown
2002 40' U320

Re: Rear A/C Trips Shore Breaker on Shut Down

Reply #10 –
When this happens does one or the other breaker feel warm or hot to touch it...this might indicate a failing breaker. Each A/C unit is on its own leg of the 240V pedestal, L1 and L2. If the breaker the rear A/C draws through is failing, it might only trip when hot, maybe explaining why it doesn't trip every time - and the front A/C runs fine on the other leg through it's own breaker. The L1 and L2 breakers are tied together so when one trips they both trip.

Also, inductive loads like the A/C compressor will create a voltage spike when power is disconnected. This will not usually trip a breaker unless it is weak and failing.
Peter and Tammy Fleming
1991 U300 GV 40 - Sold, owned for 4 years
Downsized to Roadtrek Popular 210 class B

Re: Rear A/C Trips Shore Breaker on Shut Down

Reply #11 –
Quote from: prfleming –
When this happens does one or the other breaker feel warm or hot to touch it...this might indicate a failing breaker. Each A/C unit is on its own leg of the 240V pedestal, L1 and L2. If the breaker the rear A/C draws through is failing, it might only trip when hot, maybe explaining why it doesn't trip every time - and the front A/C runs fine on the other leg through it's own breaker. The L1 and L2 breakers are tied together so when one trips they both trip.

Also, inductive loads like the A/C compressor will create a voltage spike when power is disconnected. This will not usually trip a breaker unless it is weak and failing.
Thanks...  I'll check it out.