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-   -   AC electrical question (http://www.airforums.com/forums/f427/ac-electrical-question-90004.html)

rdhoyum 04-16-2012 08:24 PM

AC electrical question
 
I have a 98 Excella 1000 with 30amp service and one AC unit.

Should the AC have a GFCI breaker in the main panel box?

I think PO may have made some changes in the main box.

TouringDan 04-16-2012 08:35 PM

I believe that the AC should be on a dedicated 20 amp regular circuit breaker. It should not be a gfci type.

Dan

Minno 04-16-2012 08:39 PM

No, the a/c should not be on a GFCI breaker. Probably won't hurt anything though. Might trip needlessly, which would be a nuisance.

Chris

HowieE 04-16-2012 08:48 PM

No The starting capacitor on the compressor motor will most likely cause the breaker to trip more times than you will be willing to but up with.

GFIs are only used where an individual can get between the receptacle and a good ground, ie a water pipe.

They are grossly over rated and misunderstood by a governing bodies that has no knowledge of electricity.

TG Twinkie 04-16-2012 10:16 PM

Here! Here! Howie!

rdhoyum 04-17-2012 09:21 AM

So consensus is regular breaker for the AC circuit. Which circuit should have the GFCI then? The main breaker??? or one of the other two. One of those is a 20 amp double pole...I'm guessing for the various wall outlets....then what would the other 30 amp be for?

I have the owners manual, but nothing technical for the trailer.

richinny 04-17-2012 10:01 AM

in my '94 34' the main breaker was 30A and the air/microwave was on a 20A. the gfi was for the bath/galley/fridge/outside outlet circuit.

HowieE 04-17-2012 10:27 AM

The above description is correct for your trailer. There is NO REASON what so ever for a double pole breaker to be in an Airstream trailer with a 30 amp service. Double pole beakers are used with 220 volt single phase systems which in a trailer system would not be required until a 50 amp service.

rdhoyum 04-17-2012 12:50 PM

Ok, I got the circuit breakers all sorted. AC on its own 20amp, the working GFCI for bath and galley, the double 20 amp breaker is circuits 3&4 for b-room, converter and liv-rm.

Here's the problem. The AC controls are connected to 120 line. The control switch, rotary knob, six pin connector is disconnected. Upon connecting it the shore line outlet(a GFCI) trips instantly.

I can only conclude it onto the roof to diagnose an AC problem.
I'm doing all this while at storage. I'll bring it home tommorrow to connect to 30 amp RV pedestal and confirm the AC works like it did before last trip.

Any suggestions on what to check/test in AC would be very much appreciated.

rdhoyum 04-17-2012 12:52 PM

One note!!!!!! The AC is off when connecting the controls. I made no attempt to turn it on......of course I have no power to do so.

DKB_SATX 04-17-2012 01:05 PM

So you're tripping a GFCI on the supply side of your shore-power receptacle, not one inside the Airstream?

Are you certain that shore-power receptacle just a mildly-annoying GFCI, or is it the REALLY frustrating arc-fault type that can trip when you're plugging in a perfectly safe appliance?

HowieE 04-17-2012 01:56 PM

If you are attempting to Plug Into a GFI as a source of power for the trailer and not talking of the GFI in the trailer you will never get power to the trailer unless you go in the trailer and turn off ALL the breakers.

What is happening there is as you plug into the GFI you are making contact with the receptacle in a sequence that is causing the GFI to see current across hot to ground before it sees hot to neutral. That will pop the breaker. The ground lug is longer than the hot and neutral and thus is the first to make contact.

Try turning off all the breakers inside the trailer and then plug into the GFI. Then you should be able to turn on the breakers inside. If at this point you still pop either the GFI inside the trailer or the one at the source you have a problem.

Report back if that is the case with details and we will go from there.

Protagonist 04-17-2012 02:05 PM

It's usually considered unwise to plug a GFCI-protected circuit into another GFCI. The first GFCI sees the next one downstream as a ground fault. One reason why campground 30-amp and 50-amp pedestals are not protected by their own GFCI; since virtually all RVs have at least one GFCI breaker inside the unit.

Remember, only one GFCI per circuit! So, if your trailer has GFCI breakers, do not plug your trailer into a GFCI-protected home circuit. If you have nowhere else to plug in, you should turn off the GFCI breakers inside your trailer and do without them for as long as your shore power is plugged into a GFCI outside the trailer.

Coventional wisdom also says that you should not plug in appliances that have a permanently-installed self-starting motor (air conditioner or refrigerator with thermostat-controls) into a GFCI. The starter circuit typically registers as a ground fault as soon as the motor kicks in.

HowieE 04-17-2012 02:30 PM

As long as we are talking the limitations of a GFI any system that has a filter cap across the input side of it's internal transformer will kick a GFI when plugged in. The charging current of the cap is enough to kick the GFI.

Lots of older audio/video equipment was so designed.

As a plant manager I had 15 steel work benches each with 12 AC receptacles mounted on them and test equipment that ranged as high a 80,000 volts. The local electrical inspector required that they each be on a GFI. They were till he left the building.


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