GFI clicking off when I plug my Camper in????

[madprinter]

I recently wired my camper and everything seemed to work fine. I was careful to make sure all the connections where secure and correct. I used a sub panel and breakers with a added ground bar. Everything worked great. I was plugging into a GFI outlet on the back of my house for power. I then added a outside outlet and cover to the side for my canopy lights and outside fan. The outlet on my house tripped. I took the cover back off and checked all my wiring. It was all good. I did'nt see any shorts in the wiring. Reset the GFI and everything worked great again. It rained yesterday after several weeks of being dry. Now the GFI keeps clicking off??? I checked for water in my connections, no moisture found. Its very hot and dry today. Where shoud I begin my search for the problem?? tryed cutting all the breakers off and it still trips??? Bad GFI??? Too much load on GFI??? I'm taking my GF camping in a week, so I'd better have some Air conditioning going. Don;t want my HOT gf to be sweeting from the outside tempature . Any help is apreciated.

[bobhenry]

Was a/c on ?

What was running ?

Are you sure you do not have your neutral and ground reversed ( yes you will still have power but it will drive a gfi crazy.)

Have you undone your last add to see if the problem goes away ?

[Miriam C.]

GFCI's fail. That is what they are designed to do and they do it. Change the GFCI and see if it fixes the issue.

[wlooper89]

A short to the trailer frame might cause the GFCI to trip in wet conditions. It could be either hot or neutral touching the frame. Nothing might happen immediately but a heavy rain or a person standing on wet ground and touching the trailer frame could complete the path to ground on the load side of the GFCI. The GFCI is checking for a very small difference between hot and neutral current. If a person completes a path to ground the GFCI will trip to protect the person.

RV manufacturers connect AC ground to the trailer frame. Apparently this does not create a conflict if DC common is also connected to the trailer frame, as usually is the case with trailer running lights. I recently modified my AC wiring to attach AC ground to the trailer frame. Now if there is a short between AC hot or common and the trailer frame the GFCI would trip immediately when the power cord is plugged in. It will trip in wet or dry conditions. Not ideal but this would tell me the problem is a short to ground or "ground fault".

A simple volt-ohm meter can detect a short between AC hot or common and the trailer frame (or separately a short to AC ground). Make sure the trailer power cord is unplugged. To me the former case seems more likely, a short to the trailer frame, if the trip happens only when conditions are wet and if the trailer frame is not connected to AC ground. But if AC ground is connected to the trailer frame and there is a short the trip would occur immediately, wet or dry, so might not be the problem in your case.

A plug in circuit tester like this can detect several different faults. The one I have alerted me to a switched hot and neutral in my AC circuits.
http://www.tripplite.com/en/products/mo ... delID=3941

Bill

[madprinter]

I'll try pluging into anoughter GFI today and see if it works. And also check for a loose connection to my frame grounding.
If I had a reversed neautral at an outlet would it still trip with all the breakers off? Thanks for all of your help.

[Steve_Cox]

All the campgrounds I've been to don't have GFI's...... problem solved.

What's a little transient voltage among friends anyway.

[BobU]

This may be way off, but I have to ask if you use an extension cord to get power to your trailer? It could be something as simple as a bad cord. The earlier thought of plugging into a different GFCI outlet is a good one, to tell if the problem is in the trailer or the GFCI outlet. As also mentioned earlier a GFCI outlet will "kick" if the neutral and the ground are shorted together (touching) somewhere. GFCI's can be a problem, but they are life-savers.

[wlooper89]

This may be way off, but I have to ask if you use an extension cord to get power to your trailer? It could be something as simple as a bad cord. The earlier thought of plugging into a different GFCI outlet is a good one, to tell if the problem is in the trailer or the GFCI outlet. As also mentioned earlier a GFCI outlet will "kick" if the neutral and the ground are shorted together (touching) somewhere. GFCI's can be a problem, but they are life-savers.

Those are all good ideas. You might start by plugging something with 3 pins into the extension cord, like a power tool or anything with 3 instead of two pins on the plug. Also inspect the extension cord insulation for cuts of breaks that could admit water under wet conditions. If the GFCI trips the problem is probably in the cord. An easy way to verify this is to plug the device directly into the GFCI outlet. If no trip I would strongly suspect the extension cord.

Next I would check an outlet in the trailer with a volt-ohm meter. I am going into a lot of detail here as experience level with AC wiring differs so much on the forum. The meter should cost less than $10 which is plenty good for this job. Set the meter to ohms and note that the meter goes full scale when the two probes are touched together. With the trailer power cord unplugged open up an AC outlet or switch and with the meter still set to ohms touch one probe to hot (black) and the other to ground (green or bare copper). The meter needle should not move indicating no short between hot and ground. Then repeat this with the neutral (white) and ground. The results should be the same if all is well.

I recommend connecting AC ground to the trailer frame if you have not already done so. There have been different opinions on this among forum members, but this is the way RV trailer manufacturers do it and that is good enough for me. With this connection in place the above tests using the meter should show the same result when touching a probe to the trailer frame instead of AC ground and the other probe to hot and then neutral. The results should be open, no meter needle movement (no connection). If the meter shows there is a connection then there is short somewhere between hot or neutral and ground (ground fault).

Bill

[wannabefree]

Let me expand on Looper's instructions a bit.

First - If you have an HF store nearby, you can pick up a multimeter for a few bucks. If not, your local Ace or box store will nick you about $!5. Either way, you pretty much need one.

Second - GFCIs work by sensing leakage current in the ground (the green or bare wire) wire. A very small leakage current is permissable, but not good. What that boils down to is the resistance (Ohms) measured between ground and hot or ground and neutral should be very high. How high? I don't know that, but probably more than 10k Ohms (10,000).

Third - GFCIs can be too sensitive, like in-laws. Try another GFCI first.

Fourth - Like Looper said, unplug the trailer and measure the resistance between neutral and ground, then hot and ground. If it's less than 10k, start looking for problems by disconnecting grounds on fixtures, charger, whatever has a ground. When the resistance goes up you are close to the culprit. Once you've found the bad guy, move the leads on the meter to the neutral or hot and ground of the suspect fixture. If you get near the same reading as you got at the start you should repair or preferably replace that puppy. If not, well, you haven't really found the problem, or you have more than one problem.

Side note - It is customary to tie neutral and ground together at one point in an electrical system (though that seems to be changing for reasons I won't go into and am not sure I understand anyway). That means inside your home's meter box, and only there. They should not be tied together in your trailer. You can tie the AC ground to the trailer frame, but I see no need.

Hope this helps,
Sherman

[wannabefree]

OH, MAN!! Just reread your post. Isolate the grounds from the neutrals in your subpanel. The problem should go away. I had this same problem when I put a subpanel in my garage off a 50A GFCI in the main panel. Like I said, ground and neutral should tie together in only one place, and that place has to be upstream of your subpanel.

[wlooper89]

I have a GFCI on the trailer after the power inlet, and experienced a trip during heavy rain. My 30A power cord is relatively new and I think that one is OK. But I was also using an extension cord (25' #12 wire) from one of the trailer outlets to run a fan that sits on a table or on the ground. The extension cord has a defect in the insulation caused by my soldering iron. That seems the likely culprit as the cord was lying on the ground. I really need to replace that cord. Should have just unplugged it but I was a bit into happy hour sitting in the screen room and did not think about it. I am glad the GFCI did its job.

Bill

[wlooper89]

Bill, in 120VAC RV wiring the ground is hooked to the frame. The main difference between RV and residential wiring is that the ground and neutral are not bonded in an RV. The 12V systen could be grounded to the frame or totally isolated from it, it wouldn't really make a difference.
Jeff

Sherman,

The quoted note prompted my switch to grounding AC to the trailer frame in addition to campground power through the power cord. Jeff is an RV technician. In my case the electrical compartment is a metal tongue box bolted to the trailer frame so I feel there is some possibility of a short to the frame. In a teardrop if the wiring is not close to the trailer frame it may not make much difference. My friend owns a Bambi Airstream and on her trailer AC ground goes to the trailer frame with a large wire.

Bill

[Larwyn]

Just a note on trouble shooting a GFI protected circuit. None of this is intended to contradict nor to correct what anybody else has said. A lot of it is strictly for your information, but it might help some understand how you can have a short that cannot be located with an ohm meter or your eyes, and how to continue after your visual inspection and ohm meter test have failed to locate a problem.

Using an ohm meter to check for shorts is a great way to find a direct short between two conductors/devices. The resistance of those readings is an indication of the quality of that short. But, the meter only applies a very small voltage to the circuit in order to calculate the resistance inserted between the two test probes. An electrical short can and often does have some of the same qualities as the insulation you find on your wires, and can read infinity (good) at the low voltage level supplied by your meter but break down at the higher voltage introduced when the circuit is energized. The ohm meter test is valid and a good idea but will not detect dielectric breakdown. In industry they use a device called a Megger which is nothing more than an high voltage ohm meter. The megger applies a much higher voltage to the circuit, usually arond 200% of insulation rating and typical readings are in excess of 100 meg ohms. We usually tested 600 volt rated cable at 1500 volts. These meters are expensive, can be hazardous to the user and harmful to any electronic devices in the circuit. I've also used a even higher voltage version known as a Hypot, which would apply up to 140,000 volts to high voltage cables to test the insulation resistance (some specs call for the test to be run at three times rated voltage or higher).

So even though a visual inspection and continuity (ohm meter) test are worth the time and trouble, and will probably locate a short if there is one, they do not totally "clear" a circuit as being short free under operating conditions. If your eye balls and ohm meter do not locate the problem, it is time to start isolating circuits. Safer and much cheaper than using a megger would be to simply isolate (disconnect) one circuit at a time until the problem circuit is identified. Then test and/or replace all the individual components of that circuit until the problem is solved.

Sherman, it has been my understanding that a GFI outlet actually operates on a differential between hot and neutral current, allowing it to detect an imbalance when there is ground current anywhere downstream of the GFI device. Have I been mislead on this?

[wlooper89]

Larwyn,

Thank you for your input on the GFI topic. I had not heard about the Megger and Hypot. Very interesting.

I gained most of my electrical knowledge by staying at a Holiday Inn Express , but your description of what a GFCI does agrees exactly with the instructions that came with my 30A device. I spent too much on that and should have split the 30A service into two 20A circuits before the GFCI's. But the instructions state very clearly that the unit only looks for a small difference between hot and neutral amps on the load side and if there is it trips very quickly. And if there is a short or overload between hot and neutral the GFCI sees that only as a load and may not trip. It is the job of a circuit breaker to trip for overload.

Your post sounds exactly right to me.

Bill

[wannabefree]

Update - I've been thinking.
When the ground and neutral are tied together in the subpanel and main panel they are wired in parallel. They share the return current flowing between the subpanel and the main panel. The GFCI sees this as an imbalance and clicks off.

The way you fix this is remove the bonding screw from the neutral bussbar. This is the long screw that goes through the bussbar and into the metal box. Then go to your local HD store and buy a bussbar. Screw that into the metal box. Remove the ground wires from the neutral bussbar and attach them all to the new ground bussbar. Problem solved.

What is interesting, though, is that this problem didn't exist the first time you plugged it in. I don't have an answer to that one, but will give you a guarantee -- if this doesn't fix your problem, I'll shut up on this topic.

Happy hunting,
Sherman