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Old 09-17-2016, 08:39 PM   #21
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If the OP actually measured a zero-ohm short between a flat blade and the round pin, that may indicate a problem. If it was low ohms, 10 or more, it may be normal, but not with all breakers off.

Is the ground supposed to be bonded to neutral in the trailer? I thought not. I thought the only ground to neutral bond was supposed to be in the house distribution panel. I think I have read (but not experienced) that a ground neutral connection in the trailer will trip a GFCI. Maybe whoever worked on the trailer made an "improvement". The wiring diagram for my trailer shows the AC breaker box has separate ground and neutral buss bars (although they may both be mounted to the steel box, I can't tell.)

With shore power off, take the cover off of the AC breaker panel and ensure that only bare or green wires are connected to the ground buss and white wires to the neutral buss.

Al
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Old 09-17-2016, 10:08 PM   #22
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Quote:
Originally Posted by John Geisen View Post
With all the circuit breakers in the trailer turned off, the GFI in the house didn't trip... until turning on the 30 amp trailer I plugged it in and then turned on all the breakers one at a time until I finally turned on the 30 amp breaker. The trailer came to life. I don't get this at all. .

John
You need to do this in reverse order.
The 30 amp is the main breaker, the others will not have power until it is on.

As mentioned above a bonded neutral can cause a gfci outlet to trip. It senses an imbalance between load and neutral since current can flow thru ground.

You need to check with 30 amp on and others off then turn on others one by one. If gfci trips with only 30 amp on then problem is in breaker box or power cord.

If it trips when you turn on other breaker then the problem is probably in the wall.
My guess would be that someone wasn't careful when drilling.
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Old 09-18-2016, 05:23 AM   #23
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All your symptoms perfectly indicate a swapped neutral and ground, likely on the back of the trailer inlet. Not of a short.

This is dangerous because your shell is acting like the neutral bus and can build up a possible voltage creating an electrocution hazard. Unplug it.

6am going back to sleep. I'll explain why later today. The electrical part, sleep part self evident.
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Old 09-18-2016, 03:04 PM   #24
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95% sure you don't have a short, but neg and ground are flipped on the new inlet.
1. You're not actually tripping breakers. Good sign that you don't have a short from the hot lead.
2. When you plug in with your described opening and then closing of the breakers, closing the 30a last you had a load as soon as you did that but still no breaker trip. Good!
3. When plugged into the gfci, the gfci trips. When plugged into the regular outlet it works fine. Good.
4. Gfci's don't care about the ground wire connected to them. Kind of a misnomer. They measure a difference in current between the hot and neutral, assuming that any difference is going to ground somewhere on the circuit. I.e. Through a person to the ground.
So what's going on.
As far as the trailer is concerned everything but the inlet is wired normally, outlet hot, neutral, and ground are all connected in your panel properly. Electricity doesn't see a problem because of this.
The ground and negative aren't bonded together in your trailer, they are not supposed to be. The ground and neutral in your house are bonded, they are supposed to be, which means that in your house the ground and neutral are electrically the same circuit!
When you are plugged into the gfci, with no load, it has no current to trip it.
When you close the 30a breaker in the trailer the load is applied and some current is applied. the hot flows normally, the neutral flows normally to the inlet back then gets redirected to the ground going into the house. This means 2 things, the gfci sees all the hot current, but no negative current coming back since it's going through the ground wire. This causes it to trip. This same scenario allows everything to work on a normal outlet because the ground and neutral are bonded in the house. So the flow is going from neutral in the trailer, to the ground wire in the inlet cord and outlet in the house, and back to the bonding between neutral and ground in the house circuit breaker. Electricity doesn't care what you call a wire, what color it is. It just wants to flow. Since the neutral and ground are bonded in the house electricity sees it as one and the same circuit. This means that current is essentially flowing 'normally' inside the trailer up to the inlet wiring. It couldn't care less.
Is this dangerous. Not normally since the shell ground is essentially always connected to the house neutral through the bonding in the house panel. This ensures all stray voltage can leave the trailer. When this can be dangerous is if there is not a good bond between the hot and neutral in the house. This 'break' in the circuit would prevent any voltage leaking to trailer ground to stay there, leaving a path through someone touching metal and the ground or any other path.
Hopefully this makes sense I know electricity can be confusing. It gets me once in a while.
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Old 09-18-2016, 08:01 PM   #25
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Thank you for taking time to give me this thorough explanation. It makes perfect sense but so does your comment about the initial surge when the converter first turns on.

Now that it appears I'm somewhat in business this is what I'm thinking and I'd appreciate your opinion on this. I've replaced the shore input receptacle once before and know what a pain it is. Thee just isn't enough wire to pull the receptacle out to work on it. Also, I have to worry about sealing it again.

So, I'm thinking that I will try the GFI receptacle again. I'm hoping it won't trip. If it does, then I have to believe that ground and neutral are reversed or the GFI needs replacing. They seem to go bad with some regularity. I can also test the GFI wiring as you suggested. I know I have the tester here somewhere.

So, please let me know if this makes sense?

Thanks again for all your help.

John
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Old 09-18-2016, 08:47 PM   #26
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John,
Makes sense to me.
Try the easiest routes first.

Plasticoat may interfere with reading so give the prongs a quick check 2 spots touching skin before hand to check zero resistance is read.

One quick thing to try is to connect the multimeter to the inlet prong on the trailer that has the ear on it, that is supposed to be the ground. Touch the other end to some metal where you can get good electrical contact with the skin, screw holding outlet to trailer is a good spot. If you get much more than zero resistance then the ground is swapped. This is because the ground from the breaker box is connected to the frame and shell, therefore there should be a clear electrical path from the ground prong through the wire to the breaker box to the frame and shell and back out to the multimeter. If you're reading high or over limit resistance then your ground is likely swapped.

This will take a few minutes before going to buy another gfci.

Sucks AS doesn't leave any slack back there.

Plus it makes me use my brain. Retirement is boring. And I like problem solving.
Joe
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Old 09-19-2016, 09:35 AM   #27
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Hi Joe,

Think I'll order the tester. Can't seem to find my other one. I took the measurements you suggested with all the breakers on. I simply unplugged the shoreline cord and took the reading. Using the meter as an ohm meter I read between ground (pin with the ear) and one of the mounting screws. Meter read the same as when touching the two leads together which was .3 ohms. The meter is set to "auto" mode so I guess I could change the settings to get a better read. I was in a hurry to get to work but wanted to try something.

John
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Old 09-19-2016, 12:23 PM   #28
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.3 ohms sounds like it should be good. I may be wrong it might be a bad gfci. Have you tried plugging anything else into the gfci to see if it trips with something else as well.

I hate electrical gremlins!
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Old 09-20-2016, 08:35 AM   #29
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Joe,

Yes, in previous posts I mentioned that I even ran a Commerical air compressor similar to the ones used at gas station (well, they used to use them) 😃 without a problem.

I ordered a new tester from the link you sent. It should be arriving tonight. I'll keep you in the loop with the results.

John
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Old 09-20-2016, 02:06 PM   #30
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This should be downstream the trailer main breaker, but I once had an issue with my house breaker popping when plugging in the extension cord. The problem proved to be a burned out water heater AC element. I had left it on when draining the heater.
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Old 09-21-2016, 03:50 PM   #31
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John,
Sounds like it might be necessary to get into the breaker panel and take some readings on the individual circuits at this point. Obviously with power disconnected and breakers open, checking wiring on each individual breaker to figure out the bad circuit. Or open all breakers, connect trailer to gfci, close 30a breaker and leave closes. Then close and open each breaker one by one to find which breaker trips the gfci. Then figure out what is on that circuit.
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Old 09-21-2016, 04:46 PM   #32
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Joe,

I received the GFCI Tester. According to the tester the outlets inside the Airstream are all fine as is the GFCI outlet in the garage. When plugging the Airstream into the GFCI outlet it immediately trips just as before. Could it be the GFCI?

On a separate note, I had an electrician install a 30 amp RV box so I could run the air conditioner from time to time as well as other circuits inside the Airstream. All went well. It now seems the only problem I'm experiencing is using the GFCI. I'm torn between replacing it, since I don't believe replacing it will eliminate the problem, and pulling out the shore input socket and checking for proper neutral. Thoughts?


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Old 09-21-2016, 04:47 PM   #33
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Quote:
Originally Posted by Endodoc View Post
This should be downstream the trailer main breaker, but I once had an issue with my house breaker popping when plugging in the extension cord. The problem proved to be a burned out water heater AC element. I had left it on when draining the heater.

That's interesting as well as a good reminder. Thanks.

John


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Old 09-21-2016, 08:42 PM   #34
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If the tester says the outlets are ok then you don't have a flipped neutral.


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Old 09-21-2016, 09:18 PM   #35
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Start the one breaker at a time method to figure out which branch circuit the issue is on. Then figure out what's on that circuit. Then we need to figure out what on that circuit could be bad.
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