HELP! Reversed polarity of the trailer itself!

dragonsdofly · September 2020

We are deep in the Michigan woods on my parents property. My brother touched the trailer this morning and got zapped. Husband has gone over everything with his multi-meter and can't locate the problem. Can anyone point us in direction to look? This only hapoens when plugged into shore power. All good on battery.

MuttonChops · September 2020

Hot Skin
Assuming this is first it has ever happened - - - expect the outlet you are using for 120VAC Shore Power is the issue. Or an extension cord if you are not using your 'known good' equipment.

Part of text from web-article:
This is often caused by the wiring in the electrical receptacle that your RV is plugged into or an improperly wired extension cord. If the "hot" and "neutral" wires are reversed

Web-article: https://www.rverscorner.com/rvshocking.html#:~:text=This%20is%20often%20caused%20by%20the%20wiring%20in,an%20electrical%20circuit%20with%20unpleasant%20or%20dangerous%20results.

dragonsdofly · September 2020

@MuttonChops, first time it has ever happened. The receptacle tests good. We are using an extension cord belonging to the family, that was here on the property. Husband is checking now. This is an "ancient" electrical system with no third wire "ground". Only 2 wires, hot and not. -Thanks

Bayliss · September 2020

@dragonsdofly, the house wiring may have a "Reverse Polarity Bootleg Ground." Google that for information and videos about it, but you can start with the link below. It could be a very dangerous condition, so you may want to disconnect the power from the house to the trailer until you get it figured out.

IMPORTANT NOTE: As you will learn from the article below, an outlet tester or Electrical Management System (EMS) are not currently (as far as I know) designed to detect this wiring issue.

https://www.rvtravel.com/rv-electricity-rpbg-update/

dragonsdofly · September 2020

@Bayliss, we immediately disconnected from A/C power. He doesn't think this can apply as it is a 2 wire system only. Husband has checked and rechecked everything he can and has come to suspect the 30 amp receptacle (umbilical hookup) of the trailer. He's wondering out loud if it's possible to have a short there causing the problem?
Anyone?

Bayliss · September 2020

@dragonsdofly, I don't have an answer to your 30 amp question. I may simply be misunderstanding the situation you have encountered, but if your reference to a "2 wire system only" (i.e., black/hot and white/neutral, only, with no ground wire) is referring to the house wiring (such as in homes built in the 60s, or earlier), I think that is exactly the situation that can create the problem.

I'm not an electrician, and have never had to deal with the situation described in the article, but if you have a "bootleg ground" and the original house wiring (i.e., the two existing wires) are accidentally reversed at the same time (i.e., reversed polarity) at the outlet as described in the article, it will make both sides of the outlet "hot." Your husband may have already done it, but I believe that the only way to check it is to turn off the house power, pull out the outlet, and see how the outlet is wired.

Electrical issues, although interesting to figure out, can be very frustrating. I hope you can get it all sorted out. Good luck with it!!

dragonsdofly · September 2020

@Bayliss, looked at the link you provided and schematic appeared to be for a "hot", neutral and ground situation. Btw, the structure on our property is an actual log cabin, built in the 1870's or 1880's. Wiring was installed in the 1920's. It was paper wrapped and stapled to the interior of the split logs. Somewhere before the mid 1960's it was upgraded to coated 2 wire. Husband and brother are preparing to disasemble from the new power supply box(installed by the utility company post millenium) to the outlet. Not much wiring in a 16' X 20' open 4 wall structure.

Bayliss · September 2020

Thanks @dragonsdofly. It sounds like it will all work out.

I guess I assumed that someone had tried to create a ground connection using a bootleg jumper. Just to keep it straight, I did some editing to my last post above to describe a situation where there was no ground wire to start with (i.e., only a hot and neutral, without a ground wire), just to clarify what I was trying to convey. In the drawing of the three outlets in that article (see below), the first outlet depicts how a standard three-wire system is connected; the second depicts a bootleg ground; whereas the third outlet depicts the problem I thought might be the issue - - a reversed bootleg, which incorrectly has the hot and neutral wires swapped.

Image: https://us.v-cdn.net/5021717/uploads/editor/ny/qykem11bkwgw.jpg

dragonsdofly · September 2020

@Bayliss, husband has opened the power box. Neutral and ground are wired into the same buss. We have "hot" leg on one wire and neutral/ground on the other leg. Neutral and ground are tied into only 1 leg. Thus the wiring is only 2 wires. Husband is attempting to wire a separate ground as we speak, for testing purposes.

MarkAl · September 2020

Confirm the longer blade of the outlet box is connected to the "Neutral" NOT the "Line" wire!

Bayliss · September 2020

Got it. Thanks! You're lucky to have a couple handymen at the old homestead.

rfuss928 · September 2020

This is a classic situation where a good "Surge Protector" or EMS would both protect the fault from becoming dangerous and probably identify the specific problem. Just sayin.....

jkjenn · September 2020

rfuss928 said:

This is a classic situation where a good "Surge Protector" or EMS would both protect the fault from becoming dangerous and probably identify the specific problem. Just sayin.....

Agree!!

My brother had a 30 amp receptacle installed at his house so I could plug in, but the Progressive EMS caught that the electrician had wired it to 240v.

This is a pretty common mistake, evidently, as electricians don't read the voltage right on the black part of the receptacle in our case (125v.)

The electrician will be coming back to makenit right.

dragonsdofly · September 2020

@MarkAl, yes, and it's correct.
@rfuss928, yes! That's what identified the problem immediately at plug in. As my brother reached to disconnect our rv line, he brushed the t@b skin and got zapped. The ems did not identify reversed polarity until we connected the t@b. And yes the ems was connected to our shore power first, showed all good, before we connected the t@b. When we connected, lights went to reversed polarity and we disconnected immediately, as my brother's fingers tingled. We have never connected without an ems being hooked up first.
@jkjenn, our ems has identified reversed polarity at a campground pedestal before, so we didn't connect there and notified the owners. We were provided another location to plug in. BUT, this time, all lights read good and we plugged in. It was as we connected the t@b to the shore power that indicator lights switched to reversed polarity. We've never seen that happen previously. It had read reversed polarity before we connected to campground pedestals. This time, not until after connection. Which is why we are trying to solve the problem while working to remove dead old growth oak trees, before they come down on our log cabin, or lordy, the t@b!
@Bayliss, still working on it, but it's dark now, so bonfire time and we'll be at tree felling and electrical diagnostics tomorrow. Hope everyone is having an enjoyable holiday weekend. Thanks to everyone for the help, advice, and suggestions!

dragonsdofly · September 2020

Et al., installation of a temporary ground and wiring reconfiguration in the power box of the cabin did NOT fix the reverse polarity indicator lights each time we plug in the t@b. We have returned everything to "as we found it" condition. So, unplanned for, we are boondocking. Battery at 12.5 after 2 days, so good to go until tomorrow.

ScottG · September 2020

odd that the EMS didn't pick up the reversed polarity ahead of time as it has in the past. Is it possible the problem is with the trailer? Maybe something bouncing loose and creating a short when last in transit? Hard to test unless you can hook it up to another source of shore power to see if the problem resurfaces.

It's easy to implicate old wiring (and that may very well be the culprit) but anything that energizes the grounded side of the T@B's 120V distribution system could cause those problems.

Denny16 · September 2020

You will need to wait until you can reconnect thenTaB to a known good shore power service, and see if the ground is still hot
cheers

VictoriaP · September 2020

ScottG said:

odd that the EMS didn't pick up the reversed polarity ahead of time as it has in the past. Is it possible the problem is with the trailer? Maybe something bouncing loose and creating a short when last in transit? Hard to test unless you can hook it up to another source of shore power to see if the problem resurfaces.

It's easy to implicate old wiring (and that may very well be the culprit) but anything that energizes the grounded side of the T@B's 120V distribution system could cause those problems.

I’d also wonder if it’s possible the 30 amp trailer cable is at fault. Again, hard to test until you have an alternate source of power.

Denny16 · September 2020

That would be the first thing to check with a meter, but unlIkely unless the cable got nicked enough to cut part why through it, since it is molded cable.
cheere

Bayliss · September 2020

@ScottG and @rfuss928, for whatever it is worth, as I mentioned earlier in this thread, both outlet testers and Electrical Management Systems (EMS) are not currently (as far as I know) designed to detect a reversed bootleg wiring issue, which is very unfortunate (and dangerous.) That is one reason I suggested it as a possible explanation. However, @dragonsdofly has apparently determined there was not a reversed/swapped hot and neutral found at the outlet in question.

I wonder if there could be a swapped hot and neutral at another outlet in the cabin (or other connection) upstream from the one the trailer was plugged in to. I don't know enough about it to say whether that could create the problem described. It will be interesting to learn if the issue goes away when the trailer is connected to a good 30-amp outlet.

Verna · September 2020

@Bayliss, that is my thought, also. There very well might be a splice, a junction box or another outlet that hasn’t been discovered that is skewing the results. While I prefer all home runs, many people do piggyback onto existing wiring to make their job easier. The piggyback doesn’t cause a problem until more modern “appliances” or RV’s are connected to it.

I only encountered two “hot” trailers (one aH one and one a temporary office trailer while at the phone company, and both certainly scared me. Luckily, I was using the handle of my screwdriver to knock on the doors (arthritic knuckle), so I didn’t take a strong hit when my hand brushed against the trailer.

rfuss928 · September 2020

Bayliss said:

@ScottG and @rfuss928, for whatever it is worth, as I mentioned earlier in this thread, both outlet testers and Electrical Management Systems (EMS) are not currently (as far as I know) designed to detect a reversed bootleg wiring issue, which is very unfortunate (and dangerous.) That is one reason I suggested it as a possible explanation. However, @dragonsdofly has apparently determined there was not a reversed/swapped hot and neutral found at the outlet in question.

I wonder if there could be a swapped hot and neutral at another outlet in the cabin (or other connection) upstream from the one the trailer was plugged in to. I don't know enough about it to say whether that could create the problem described. It will be interesting to learn if the issue goes away when the trailer is connected to a good 30-amp outlet.

I have a cabin wired in ~1960. There are ground related ghosts there that baffle me still after years. I understand electrical systems and grounds and bonding. I just would not attempt to trouble shoot a system I have never seen with so many details that could cause this issue. It seems , like you pointed out, there is probably something "upstream" related to this connection's issue. I can only hope the OP finds a workable solution.

dragonsdofly · September 2020

Et al., we are home, plugged in and all is well with the t@b's electrical systems and ems. The problem has to be in the cabin wiring. The cabin is being set up for winter and we pull the power until next year. Obviously, we will return next year and follow everything from power box to the outlets, step by step and inch by inch, but we'll do it fully prepared for boondocking.
DH says it will be relatively easy, as there are only 4 outlets, 2 light fixtures and a ceiling fan in this straight forward 2 wire system. And it's kinda easy to follow how it's wired. Thanks for all of your responses! @Bayliss, husband is going to study and understand the reversed polarity bootleg situation before tackling the job.

Image: https://us.v-cdn.net/5021717/uploads/editor/g0/0k1arxw9ol7e.jpg

This is an interior photo of our cabin. As you can see, tracing the wiring and connections will not be difficult.

ChanW · September 2020

Ahhhh.... Cabin life!

Sharon_is_SAM · September 2020

Very cool Denise. Look at those log rafters!

dragonsdofly · September 2020

Yes, guys, wasn't kidding about it being an actual log cabin. It is not a facsimile, or something made to look like a log cabin, it is one. As you can see, it won't be hard to trace the wiring. Thanks again to everyone who commented or provided information.

Denny16 · September 2020

This is easy, lights and outlets should be two different circuits. Get a outlet tester that plugs into the outlet, it will check for and display connection faults, like neural and hot reversed, ground or lack of one. I would pull each outlet out, and check the connections, see that they are wired correctly, as noted above and a hot (black wire) has not been swapped with the neutral (white wire). I think this, or a loose wire in one of the outlets is the issue.

The plug in tester will tell you which outlet, if any have this issue. You do not have a third wire ground run, you might want to consider getting a roll of 12 ga. Green wire and run a ground to the outlets. Do you have fuses still or circuit breakers? If the later, there should be a hot, neutral and ground buss inside it.

You would run the ground circuit from the ground buss and tie the neutral and ground together in this box, and no where else, if this box is connected to the meter and is where service comes in from. The neutral and ground buss are only connected at the meter incoming service circuit breaker box. Your Service/circuit breaker box, should have a ground connection (even on a two wire system) connected to a purpose made ground rod driven 4-5 feet into the ground near the box.

You need to be sure the outlet for the TaB has a ground connection to the circuit box ground buss. Without a ground, even a correctly wired outlet connected to the TaB can allow for excessive float potential voltage on the trailer surface.

cheers

tybladesmith · September 2020

Bayliss's post from Sept. 5 https://www.rvtravel.com/rv-electricity-rpbg-update/ Mike Sokol points out the use of a Non-Contact Voltage Tester to identify a Reversed Polarity Bootleg Ground and also RV hot skin test.  https://www.youtube.com/watch?v=GuWX9wJwvtU

A recommended NCVT. This would also detect a hot ground in a receptacle or help identify where a junction box is miss-wired, with out taking any connections apart.
https://www.amazon.com/Fluke-1AC-A1-II-VoltAlert-Non-Contact-Voltage/dp/B000EJ332O/ref=sr_1_3?crid=9CNVPPK50CDZ&dchild=1&keywords=fluke%2Bnon-contact%2Bvoltage%2Bdetector&qid=1599581261&sprefix=Fluke%2BNon-Contact%2Caps%2C156&sr=8-3&th=1

We should start carrying an NCVT along with a GFCI receptacle tester and multimeter!

Sorry for geeking out but a very important point for us trusting an Electrical Management System (EMS) to protect the life of our barefoot grand children.

ScottG · September 2020

Great discussion. I was finally able to read the link on RPBGs provided by @Bayliss and given the entire body of evidence I'm casting my vote as this being the source of the problem.

I'm a little unclear about this statement:

dragonsdofly said:

@Bayliss, husband has opened the power box. Neutral and ground are wired into the same buss. We have "hot" leg on one wire and neutral/ground on the other leg. Neutral and ground are tied into only 1 leg. Thus the wiring is only 2 wires. Husband is attempting to wire a separate ground as we speak, for testing purposes.

I assume by the "power box" you mean the panel where the circuit breakers or fuses are installed. Your first statement referring to the "neutral and ground" being "wired into the same buss" implies a three-wire system. However, your second statement clearly states that you only have a two-wire system.

Does the first statement refer to the wires coming into the panel from the meter outside? Does the second statement refer to the wires leaving the panel to feed the cabin's branch circuits (including the outlet you have the T@B plugged into)?

dragonsdofly · September 2020

@ScottG, I am referring to the power box where the power comes into our cabin. There is a ground installation into the cabin and the ground is tied into the neutral buss in the power box. All neutral wires are also tied into the same buss. There is also a "hot" buss and the power wires are tied into it. For each outlet there are only 2 wires, one white and one black. There are no ground wires to/in any circuit, only into the power box. As stated previously, the box was installed post millennium by the utility company. There is no electric meter. We pay a fixed fee for the power we use a few days a year. Husband suspects the situation @Bayliss detailed. We are home now and all is good. Whatever the wiring problem, it has never bothered the 1940's oscillating fan, the 1940's or 1950 fridge, the one lightbulb or wall switch. All of that works properly, as it has since approx 1960, when the wiring was upgraded. Arrival of the t@b upset the apple cart. This is a major project on our list for 2021. Already planning!

dragonsdofly · September 2020

@ScottG, yes, from outside there is a ground. A large cable, tied to a metal stake driven into the soil outside the foundation is tied into the power box buss, all neutral wires are also tied into the same buss. Only 2 wires leave the box for each circuit, one white and one black.

HELP! Reversed polarity of the trailer itself!

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