Hot and Neutral Reversed

[spat61]

My $8.00 circuit checker shows that my hot and neutral are reveresed when connected to 30 AMP shore power. But, when I switch to the genny, the indicator is two amber lights in a row- that means normal.

Now I must say, I did nothing that I am aware of to cause this situation. Nothing changed electrically to my knoweldge. I did notice the hot/neutral reversed condition at my last over nighter. The campground was new with concrete pads and almost empty for this time of year.

I'm looking for suggestions. I have power to the breaker box, between the power junction box and two interior wall outlet boxes are the transfer switches, two of them. The two outlets are not connected to the breaker box, unusual that they are on when my main breaker is off.

My coach is a 2002/2003 30' Gas. Genny is Onan 5500. Any ideas from an elctrician would be appreciated. What could cause this situation? Thank you.
Steve

[Splitrock]

I'm not an electrician but I did stay at Holiday Inn Express one night.

Did you check the campground plug with your tester? Or is the reverse showing up on multiple plug sites. It's easy to check any wire on your trailer with a multi meter with the power off. Start at the plug.

I'd take the generator all the way out of the test.

Gary

[samb]

I am not an electrician, but I did work in Oregon State Parks for over 30 years.

Did you check the source of your shore power with your tester? That is the first place I would look. Test your tester in a known power source on occasion and then trust it. I leave my tester in the trailer plugged in at all times and it is the first thing I check after hooking up.

Every year before the start of camping season at the state parks I would make sure that all the electrical hookups were working properly. About 15 to 20 times during the year I would get a complaint that some one was getting a shock from touching their trailer. Sure enough, the hot and neutral had been switched by a camper that thought he was an electrician and he would "fix" the wiring to match his trailer. Locked electric boxes were the only way to prevent this. Of course, then we would get the complaint that our electric was screwed up and 15 or 20 times during the year we would get an offer to "fix" the problem if only we would unlock the box.
Sam

[DaveFL]

Samb has the best answer, plugging into good sources to check meter, then use it every time you plug in, part of the procedure before attaching landline, know plug works and is wired right.
Second part is you have live circuits when the breaker is off, I would want to know how they are getting power. Are they wired directly to the transfer box?

AS did wire a separate circuit for the A/C on mine, you can only run one at a time on mine by throwing switch found in ceiling cabinet just to the left of the sink. But when on Generator both A/C's can be run. See if those outlets are hot when you change the switch if you have one.

[garry]

The CG pedestal was wired incorrectly or your RV plug is wired backwards.

[lewster]

1. check the shore power and certify that it is wired correctly.

2. check the shore power cord to be certain that the plug was put on properly (do this with a continuity tester)

3. check the transfer switch(s) with a meter and be sure that THEY are wired corrrectly.

It is obvious that the generator is good thru the transfer switch and into the breaker box, so my guess (and it's only a guess as I am not there to verify the wiring) would be improper wiring AT the shore power source or at the transfer switch.

You can check color coding in the wiring, but that is not always reliable.

THIS IS IMPORTANT! An experienced electrician can and probably would do this testing on a life circuit. UNLESS YOU ARE TOTALLY FAMILIAR WITH AC CIRCUITS, DO THIS TESTING WITH THE POWER REMOVED. Molten VOMs are not a pretty sight, and they smell even worse when toasted!!

[spat61]

Lew,
Could my power cable end cause the hot/neutral reverse. The end is moulded and is definately original, but the blades are abused with some green stuff on the blades and they are not real tight in the mold. Is there a good way to check this out or would it be better to just purchase a new cable? Or can I cut off the male three prong and replace it with a new male end?

Also, there are two transfer switches. Is one for the generator and the other for shore power? I do understand the purpose is to switch from shore power from generator and vice versa, but why two?

Thanks for your help.
Steve

[TG Twinkie]

I think the reason your generator looks OK to the tester is that it has no earth ground unless you provide one. Just because the power cord has a molded end, it means nothing. It could be wired into the panel inside your trailer the wrong way. Do you have the 30 amp RV plug and receptacle wired at your home? If so the RV receptacle is marked as to where the ground wire and the neutral (look for WH or WHT on the back of the receptacle). The white wire should be connected to the neutral terminal, the ground to the ground connection, that only leaves the black and one terminal to connect it to. I am an electrician and I will caution you to play it SAFE. If you are not comfortable trying to troubleshoot, locate and correct the problem, then hire someone qualified to do so. Can you post some photos of what you have?

[garry]

Transfer switch determines where your power comes from the default is shore power and once the generator is started and a short delay (20/30 seconds) the transfer switch automatically transfers to the generator.
Once the generator is shut down it switches back to shore power.

The only reason I can think for the second transfer switch is you have an inverter installed.

If you have an inverter that could be the problem.

I would suggest you plug your tester in some other outlets to verify reversed polarity in all outlets.

[spat61]

Garry,
Yes to the Inverter. It's a 400 Amp that does not work. This could be my problem? Can I just disconnect the inverter from the system? And, disconnect the second switchbox? Thanks.
Steve

[garry]

Have you tried other outlets to check for polarity errors?

The transfer switch for the inverter will make some outlets "hot" when the main breaker is off.

Yes, you can disconnect the "output" of the inverter to see if that is a problem but it may be the outlet you tested is wired wrong.

Most inverters tie the ground to the neutral and this will cause a fault condition that will trip the GFCI outlets in the RV.
To get around the problem some folks install the inverter to isolated outlets not tied into the main breaker box. The inverter has it's own breakers.

[spat61]

Garry,
You are giving me an education. Yes, I did check three different outlets in front, middle and rear of MH. All were showing a red for hot/neutral reverse. I own this MH three years this month and this situation just popped up during my last trip about two months ago. I would blame it on the last CG pedestal, but I just plugged into a known properly wired 30 Amp connection at a neighbor's garage. It is the trailer type female connector, and is wired per code. I still get the hot/neutral reverse lights.

My next step is to remove and replace the hard wired power cord at the juction box at the point where shore power enters the MH. The male connector on the cord has loose blades that I'm told could possibily cause a disrupted neutral. Does that make sense? I'm shooting in the dark.

After that, I'm going to disconnect the inverter. Your thoughts are probably correct in that the Inverter could well be the reason I have two hot outlets with the main CB off. It's a very small inverter, 400 Amps and the original window price sheet states it is for T.V. only. Can you suggest any precautions I should take when disconnecting the inverter?

Thanks for all your help.
Steve

[TG Twinkie]

If it were a 400 amp inverter, it would be half the size of your motor home. I think it is 4 amps, especially since it says "For TV Only". You could cut the end off of your existing power cord and replace the plug. If the rest of the cord is in good shape, that would be the most economical. If you are showing reverse polarity I would check the circuit breaker box in your trailer. The black wire in the cord should be connected to the bus that feeds the circuit breaker and the white wire should be connected to the neutral bus with all of the white wires from the internal AC wiring of your trailer. The neutral bus in the trailer should not be connected to the body or frame of the trailer. ONLY the ground bus should be connected to the body/frame of the trailer

[spat61]

TG,
I probably should have said 400 watts.
I will follow your instructions. Thank you.
Steve

[garry]

Reversing neutral and hot is not something that just happens it is caused by a wiring error.

Are you sure the tester is showing reversed or could it be showing a missing ground or missing neutral?
Any particular reason you checked the wiring or were you experiencing problems.

A problem with open neutral or ground is a common problem and comes from flexing the power cord breaking the wires inside or rock and roll from bouncing down the road over time can cause open connections.

If your inverter goes to separate outlets then I doubt that is a problem.

The next step in troubleshooting is to use a meter to ohm out what is going on.

[spat61]

Garry,'
I just happened on one of those yellow tester's at Lowes and plugged it in. No particular reason, but what a surprise to see a red led lite up. I had no idea that I had any problem before plugging that tester in. I start trouble shooting tomorrow, beginining with the power cord. The male plug looks like it went thru WWII. Thanks again and I'll keep you posted.
Steve