Concession trailer electrical nightmare

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Jb’s

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Aug 11, 2022
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Hello. I am new to the forum, and have never posted a question in a forum before today, but the problem I am facing has me completely beside myself.
I have recently purchased a concession trailer, it is a 2014, with one previous owner. I was told the trailer had some electrical problems that needed sorted out prior to purchase. I bring the trailer home, plug it into my r14-30a outlet, and realize there were obvious problems. The lights flicker when the freezer is turned on, the breaker for the fridge seems to be working in conjunction with the lights (fridge will not work without both breakers on), the outlets show a reversed nuetral and hot wire, the vent fan comes on with the air conditioner. The freezer, and fridge also seem to kick off and on as if they are losing power etc, etc. ...but when I run the trailer on generator power, everything works perfectly. I have checked the plug for good continuity, the extension cord, and have checked my outdoor 220 outlet, and everything is working fine. This problem makes no sense to me. Any help would be greatly appreciated.
 

Lou Schneider

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Mar 14, 2005
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Welcome to the RV Forum! In all honesty, it sounds like you need some professional help to straighten out that mess. You may have too much voltage drop along the shore power cord when it's confronted with the heavy starting surge of the refrigeration compressor, the reversed polarity needs to be located and fixed, etc. A couple of hours with a good electrician can work wonders.
 

Pedro Dog

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South Shores, CA
I was told the trailer had some electrical problems that needed sorted out prior to purchase.
Where these problems supposedly sorted out?

If they were and everything is fine on a generator, you may be having an issue with your home wiring.

flickering lights usually mean a problem with the neutral.
 

kcmusa

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Jul 29, 2015
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What’s different when on generator? Does it have a transfer switch?
 

Pedro Dog

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In your home the neutral is bonded to ground at the service panel. This bond provides a 0 volt reference to the +120VAC and the -120VAC. Inside the RV the two 120VAC lines are used to power different things and use the neutral as the return path.

When the neutral to ground bond is interrupted, the 0 reference is lost and although the voltage between L1 and L2 is still 240VAC, individual 120VAC loads in the trailer can see different voltages other than 120VAC. One leg can go up to 240 and the other to 0. Usually one will go to maybe 150 and the other will go to 90 (150+90=240)

Some things will burn up and some things will barely work or lights flicker.

The generator doesn't have this issue, it handles the neutral differently.
 

Gary RV_Wizard

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West Palm Beach, FL
Since this is a concession trailer rather than a factory-built RV, could you please clarify it's shore power need and the generator it uses? Before we go down too many rabbit holes, please describe what sort of electrical service this trailer expects to get.

RVs designed with 30A shore connections do not use 220v, but RV 30A/120 is probably insufficient for a food concession vehicle. You mentioned a NEMA 14-30R outlet, which is a different animal than the RV 30A/120v outlet, designated NEMA TT30R
 

Pedro Dog

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I can't see it being anything but a 240 trailer. He is running a refrigerator, freezer, air conditioner, lights, fan and who knows what else.

fridge will not work without both breakers on

What I believe is happening is that the one breaker uses L1 of the 240VAC and the other breaker uses L2. So when the 120VAC fridge gets power from L1 via it's own breaker, the return current on the neutral line can't find it's way back to the source (wall outlet to the power panel) because of a bad neutral connection there.

Since CB1 (L1) and CB2 (L2) both use the neutral for their respective return paths, and they are still connected inside the trailer, Basically the refrigerator gets 120VAC from CB1 and uses CB2 for the return path. This creates a wild line voltages inbalance, thus the symptoms.
 

Groo

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UP of MI
My immediate thought were bad ground/neutral. My secondary thoughts were "shouldn't that be full of GFCIs? And why aren't they tripping?"
 

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