Hot skin?

[CoffeeGuy]

Why do I have hot skin when I plug my bus into shore power?

I thought it was because I did not take the ground bus bar and bond it to the bus body, so I ran a 6 gauge wire from the ground bus and bolted it to the bus frame. When I plug the shore power back in, I still have a hot skin, as demonstrated with a non-contact a/c voltage tester.

[TaliaDPerkins]

Apparently you still have a bad ground bond between your ground connection and separately a connection you should not have between some hot conductor and the skin . . . or you would be popping a breaker?


You need an old electrician and a young electrician.


"The power of Ohms compel ye!"

[ewo1]

Originally Posted by CoffeeGuy

Why do I have hot skin when I plug my bus into shore power?

I thought it was because I did not take the ground bus bar and bond it to the bus body, so I ran a 6 gauge wire from the ground bus and bolted it to the bus frame. When I plug the shore power back in, I still have a hot skin, as demonstrated with a non-contact a/c voltage tester.

HERE is an interesting thread on bonding. It might be helpful!

[TaliaDPerkins]

If you start breaking the problem into sections, you can make progress.


Depower, lock off, and disconnect your sources (battery/inverter). Measure Ohms between you busses and skin. There should be a low ohms connection between ground and the skin. There should be megaOhms between the hot busses and the skin. At least one will show a low ohm connection to the skin. Start disconnecting the outbound wires from the hot buss and measuring the Ohms between the bus skin and the wire end -- at least one will apparently be showing low ohms to the skin. That/those one/s will be needing to be looked at for a bad insulation touching metal.


At a guess that will get it.


I can tell you I'd start there.


Check all exposed conductors for unexpected voltage before you handle bare wire ends! You have something funky somewhere!

[Booyah45828]

Is your ground and neutral bonded at the source?
Is it bonded at your bus's panel?
Is the bus body and frame ground strap in place?

All this can be checked and solved with an ohm meter. So get/use an ohm meter and start checking things.

You might also want to try and narrow down which device on the bus is making the stray voltage. In the shop we had an old alignment machine that had a transformer on it's way out. If I used the wrong extension cord(open ground) with it the case of the machine would give a tickle every time you touched it.

[DeMac]

Originally Posted by CoffeeGuy

Why do I have hot skin when I plug my bus into shore power?

I thought it was because I did not take the ground bus bar and bond it to the bus body, so I ran a 6 gauge wire from the ground bus and bolted it to the bus frame. When I plug the shore power back in, I still have a hot skin, as demonstrated with a non-contact a/c voltage tester.

--------------

Note the B&W label, on the Ground Bar, which reads 'Chassis Ground'.

●I don't see the #6 bare, bonded to the Ground Bar, in the photo. (?)

●On the frame rail, (What method was used?), to bond the #6Cu to the frame? ☆Cu or Al Gnd Lug, Cu bolt? NO Self Tappers Allowed to Bond Ground Lugs. ☆Also, was a grinder used to clean the rail? Photo, pls...

●Does the power pedestal have its own Ground Rod? (Add one w/ bare#6)

●How many accumulative feet of Grounding conductor to the nearest Grounding Electrode?

●Are there any appliances currently plugged into the outlets? The appliances have their own case/chassis grounds, too.
☆For diagnostic purposes, Unplug everything while you search, then plug them in one-at-a-time, while the system is on.

●Turn off ALL Breakers, Before you plug in. Then attach shore power, Test skin, Turn on Main, Test skin, Turn on One Breaker, Test skin.....(repeat)

●Verify the quality of the grounding conductor & ampacity of the SO cord, used to electrify panel from the pedistal.

Physics Fact:
Electricity is ALWAYS searching for the shortest path (path of least resistance) to the Earth (Ground). Home.

The bus's skin (and Grounding Conductors) OUGHT to have lower resistance than any of the Current Carrying Conductors(hots) or Grounded Conductors(neutrals).
If this⤴ were true, one or more Overcurrent Protection Device(s), no matter their souce, would trip AND identify the shorted circuit(s) via the tripped breaker, fuse, gfci, etc...

Lower the resistance of the skin FIRST and the shorted circuit will quickly expose itself.

[TaliaDPerkins]

Originally Posted by DeMac

Lower the resistance of the skin FIRST and the shorted circuit will quickly expose itself.

Lower it's resistance to Ground. Wire wheel a bare metal spot, clamp a ground to that, etc. There should be no resistance between that skin and frame, but maybe there is.

[CoffeeGuy]

I appreciate all of the suggestions as to what I should inspect. I got side-tracked for a couple days, working on my recirculating shower, but now that I worked out that solution I will get back to the hot skin issue in due time.

My ground bonding is bolted to a section of unistrut that my mini-split hangs from. The mini-split frame was hot, so I think the ground is good... but I will check with my ohmmeter when I follow through with all of these suggestions.

I will follow up with this thread as I progress. This isn't something I want to ignore as I do understand the seriousness of the situation.

[Bobby]

I had that problem before and for me I changed outlets I had the bus plugged into. I didn’t have the issue with running on a generator but only when it was plugged in. In my case I had it plugged in with a regular extension cord for testing purposes so I simply changed to an outlet on a different circuit and the issue went away. Just a thought….

[CoffeeGuy]

After taking the time to run some tests, including running off the generator, I determined that the issue wasn't my bus, it was at the shore power outlet. Switching to a different outlet (as suggested by Bobby) solved the problem.

Unfortunately, the new outlet has more things running on it so I am likely to trip a breaker if I run the mini-split.

Thanks, all! Methodical testing always narrows the problem if not resolving it completely.

[Bobby]

Glad I could help.

[Booyah45828]

Good to know that you narrowed it down away from what you did on the bus. Is your house older by chance?

Reason I ask is that older houses often didn't run grounds, and some of your really old knob+tube houses you couldn't tell between hot and neutral up in the attic. If they have hot+neutral flipped on the outlet and the bus's gnd+neutral was bonded, you'd create a hot skin condition. I don't think one of your plug in outlet testers would be able to tell that due to no ground present at the outlet.

I've also seen guys wire outlets with bootleg grounds create a hot skin too.

I wouldn't sign off on this with an outlet change, figure out the problem and fix it. If you wired the bus you can fix the house wiring.

[Danjo]

Is that a reverse polarity issue then?

[TaliaDPerkins]

Originally Posted by Danjo

Is that a reverse polarity issue then?

Hot for Neutral swap? It does sound like it, doesn't it?

[cadillackid]

Originally Posted by TaliaDPerkins

Hot for Neutral swap? It does sound like it, doesn't it?

with a good ground, a hot / neutral swap should result in a tripped breaker

[Booyah45828]

Should trip it, yes.

But if there is no ground to the outlet, and it has a bootleg ground hooked to the neutral(which is actually the hot now) And the bus doesn't have a ground rod and is relying upon the outlet's ground.

Then yes, it will shock you without tripping a breaker, at least not on the bus, and possibly not on the house.

A lot of hypotheticals there, but it's the possibility that my mind has jumped to.

FWIW, you wouldn't need the bootleg ground in the scenario if the neutral and ground are bonded in the bus's panel. They shouldn't be bonded in this scenario, but if they are, it would cause the same issue as having a bootleg ground would.

[CoffeeGuy]

Originally Posted by Booyah45828

Good to know that you narrowed it down away from what you did on the bus. Is your house older by chance?

The house looks old, mid nineteenth century dog trot style log cabin, but built in 1985. The bus is plugged into the barn, which actually is from the mid nineteenth century, but the wiring was added about 30 years ago. The wiring in the barn may be the issue on that one outlet. The others seem fine. I'll have to take a closer look at it when I have some time. Thank you for mentioning it!

[HamSkoolie]

Originally Posted by Bobby

I had that problem before and for me I changed outlets I had the bus plugged into.

Originally Posted by CoffeeGuy

After taking the time to run some tests, including running off the generator, I determined that the issue wasn't my bus, it was at the shore power outlet. Switching to a different outlet (as suggested by Bobby) solved the problem.

While installing new batteries into my RVIA 21.5' fifth wheel one day I found (that tingle gave it away) that my trailer had a 110 on the skin. YIKES.
Initially thought we had an electrical issue in the trailer after the shore power came in.
What I found was that the tenant (trailer stored at a rental we own), after I'd installed a swamp cooler and asked if they could put the inside grille (and power switches with power cord) themselves. Great tenant so they said yes. Turns out that he ran the grille screw right through the hot wire which then put juice on the ground side. 1940's house and didn't pop any breakers.
Found the issue using one of those plug in the wall testers you can get just about anywhere and tells you if your outlets are wired correctly. When testing the outlet the trailer was plugged into (top of the outlet with the swampy) things weren't right. Unplug swampy and things were right.
WTF? multimeter on the unplugged swampy cord had me thinking something was wrong in the swampy but no. As soon as I pulled the grille I saw that the screw had caused the penetrated the power cord.
Amazing that with all that water no one had been seriously injured.
First thing I do when buying a house it test all those outlets. Now I test cords.... actually found a factory extension cord with crossed wires once. Now I test everything!!!!!!

[Danjo]

Originally Posted by HamSkoolie

While installing new batteries into my RVIA 21.5' fifth wheel one day I found (that tingle gave it away) that my trailer had a 110 on the skin. YIKES.
Initially thought we had an electrical issue in the trailer after the shore power came in.
What I found was that the tenant (trailer stored at a rental we own), after I'd installed a swamp cooler and asked if they could put the inside grille (and power switches with power cord) themselves. Great tenant so they said yes. Turns out that he ran the grille screw right through the hot wire which then put juice on the ground side. 1940's house and didn't pop any breakers.
Found the issue using one of those plug in the wall testers you can get just about anywhere and tells you if your outlets are wired correctly. When testing the outlet the trailer was plugged into (top of the outlet with the swampy) things weren't right. Unplug swampy and things were right.
WTF? multimeter on the unplugged swampy cord had me thinking something was wrong in the swampy but no. As soon as I pulled the grille I saw that the screw had caused the penetrated the power cord.
Amazing that with all that water no one had been seriously injured.
First thing I do when buying a house it test all those outlets. Now I test cords.... actually found a factory extension cord with crossed wires once. Now I test everything!!!!!!

I worked on a friends house that had a similar problem. Hot sink! I forget what else had to be touched, but it would give a good zap. I got to digging. It was a skinned wire in a metal junction box. Why didn’t it trip? Corroded/dirty ground clamp connecting the ground wire to the grounding rod

[HamSkoolie]

Originally Posted by Danjo

I worked on a friends house that had a similar problem. Hot sink! I forget what else had to be touched, but it would give a good zap. I got to digging. It was a skinned wire in a metal junction box. Why didn’t it trip? Corroded/dirty ground clamp connecting the ground wire to the grounding rod

Back around 2008/9 I did a lot of work on my sister and brother in laws condo. The BIL had lived there for a long time as a bachelor and there were things like hole at cut through drywall to run new TV cables, a section of wall that a small dog had dug through both sides of an expandable gate intended to keep it on the linoleum, deteriorating shower walls (tiles falling off en mass), and the BIL said "can you look at this" then turned on a circuit breaker which immediately snapped back open. "It's been that way since I moved in" he says.
Well the dining area chandelier and a wall outlet also didn't work. Being a condo I told him I'd look but I wasn't doing anything major with electrical since it was a condo with shared walls and such.
I pulled he wall plate off the inop outlet and there it was. A ground screw on the outlet hadn't been screwed in and was instead welded to the metal box which was connected via metalic conduit.
Surprisingly, after several decades, the outlet, chandelier, and circuit breaker all started working.
Such a simple fix and it had been ignored for at least 20 years.