electrical short 1977 Airstream

[daleclem]

I had a new overhead light switch, and air-conditioner replaced and enjoyed a week of camping in two locations in my 27 ft. rear bath 1977 Land Yacht. I got home and plugged the camper in and immediately tripped the GFI outlet. The 12 volt battery was still working and the lights worked. Then they stopped working, so there is no power in either system working. I plugged it back into the truck and the running lights work, but nothing else. Of the four breakers in the bathroom, the lower left was thrown. I'm thinking I have a short. Any ideas where to start?

[BayouBiker]

I assume you mean you plugged the shore power into a GFCI outlet on the house and it tripped.

You say the 12 V system stopped working, is that because the batteries are drained? If so charge them so you don't damage them further.

If you don't have a charger, plug into a non GFI circuit so the batteries will charge.

Once we get the 12 V system running we can look at where the ground fault is. Neutral and ground are bonded on the trailer so no risk of shock.

[daleclem]

Yes.Thanks for responding. I've flipped the breaker off that had tripped and replugged to shore and the lights and air-conditioner worked. This breaker carries the refrigerator and so I plugged it into a shore extension chord and it started up so I know the short is not in the refrigerator. The battery is charging now. It could be a bad breaker.

[BayouBiker]

That's good news. Because the neutral and the grounds are bonded (tied together and bonded to the trailer frame and shell) and the trailer itself is most often not well grounded, external GFCIs will not and cannot function correctly so their purpose is defeated when the trailer is plugged into one. This is because the GFI is designed for and presumes the devices plugged into them have an isolated floating neutral and independent or no ground like a hair dryer or a drill or saw.

However if a GFCI does trip when a device that has a bonded neutral and ground is plugged in, it generally indicates a rapidly fluctuating current or voltage or both which indicates a loose connection or weak breaker or whatnot. And it can be difficult to find. Hope this gives you a hint on what to look for, and hope you understand that the trailer defeats external GFIs so their is little value in using them other than the possibility if points you to a connection issue. Could also be a phantom issue, though less likely.

[TG Twinkie]

The above is BAD INFO.

THE NEUTRAL AND GROUND SHOULD NOT BE BONDED IN THE TRAILER.

The panel in the trailer is considered a sub panel.
The only bonding location is in the MAIN panel which feeds the receptacle where the trailer plugs in.

[rmkrum]

TG Twinkie is Absolutely correct. Under no circumstances should AC power ground (safety earth, green wire) and neutral (power return, white wire) be tied together anywhere in the internal Airstream power system. It’s absolutely a “sub panel” per code.

It’s a serious safety hazard. The only bond should be in the service panel for the house, the pedestal, or a bonding plug installed in a portable generator.

If it’s wired any other way it’s an electrical code violation and under some circumstances could cause the exterior skin to become ‘hot’ which can be fatal if touched whilst standing on damp earth outside.

I’m in the process of installing a front power inlet on my rig, with a manual power source selector switch, and one of the things I will be very carefully double checking with a multimeter is the total LACK of a connection between neutral and ground in the shore power cable and the associated wiring once I have it all properly installed. Not something to be trifled with.

I’m also putting in a hard-wired internal EMS/surge protector to verify power is properly connected and voltage is correct every time I plug into a power source. Getting zapped is not my idea of a good day...

[BayouBiker]

Yes, sorry I provided bad information, I guess it's been too many years since I spec'd out power systems. I will need to go back to school on this. Disregard what I said, the GFI does function as intended and there very well could be a ground fault in the subject trailer.