Shocked by Frame to Ground

**Herk7769** · 08-14-2014, 09:09 AM

While packing up to come home from the Rally, I got a shock when touching a tire hub and kneeling on the ground. It was not "a lot" but it got my attention.

More of a tickle than a strong shock, I was still concerned.

At our intermediate stop, the shock I got was much stronger when touching any frame part while kneeling on (or touching) the ground.

The Franks was not complaining about this so I assumed (correctly as it turned out) that incoming power was not the problem.

Home, I metered power from the metal to the dirt and got 39 volts AC and 14 volts DC. Scratched my head for a while and decided it had to be a neutral/ground problem and traced it to a bad connection where the Neutral and the Camper Ground were bonded to the frame.

Removed, cleaned and reinstalled the screw/terminals and we are now back in the "No Shock" zone.

doodler · 08-14-2014, 09:52 PM

Thanks for the post Herk. The neutral is a current carrying conductor. Bad connection can very well energize the frame and any metal parts attached to it. I have seen that happen in tin mobile homes also.

mark0224 · 08-14-2014, 10:01 PM

I worked for the phone company for a few yrs a while back and we had a meter that we were required to check mobile homes with before we did any work. Mobile homes can get energized enough that it can hurt you severely.

**ependydad** · 08-14-2014, 10:52 PM

Any chance you took a "before" picture?

BigBaron · 08-15-2014, 01:04 AM

You mentioned the "No Shock Zone." I take it you're familiar with Mike Sokol?
http://www.noshockzone.org/rv-electrical-safety-part-iv-hot-skin/

Oaklevel · 08-15-2014, 05:21 AM

Thanks for passing the info along knowledge is a very important part of RVing safety. I had forgotten (doing more of that lately) We had the same issue with 1988 Terry a many moons ago.

Last month I had to rescue a camping neighbor that got his arm caught in his awning as he put it away looked painful...........

**Herk7769** · 08-15-2014, 06:05 AM

Quote:

Originally Posted by ependydad

Any chance you took a "before" picture?

Doug, that WAS a "before" picture!

The corrosion was rust at the threads and under the bolt head.

**Herk7769** · 08-15-2014, 06:09 AM

Quote:

Originally Posted by BigBaron

You mentioned the "No Shock Zone." I take it you're familiar with Mike Sokol?
http://www.noshockzone.org/rv-electrical-safety-part-iv-hot-skin/

Excellent article. Will also check for that just in case.
Re-bonding seems to have fixed it, but perhaps the now solid ground is masking my problem. Will let you know.

If the Neutral and Hot were reversed at the campground, the power conditioner should have alerted me with a "red" indicator light though...

Also you would have 120 volts between the Neutral Buss and the "Ground" (green/bare wire) Buss if the Neutral/Hot was switched (Reverse Polarity) at the campground (or at the socket - in the article).

There was less than a volt when measured between those two; yet 39 volts between the frame and the dirt outside.

offroad · 08-15-2014, 06:26 AM

Would this normally be located on the frame close to the converter or near where shore power is connected?

Might be good to check this periodically.

**Herk7769** · 08-15-2014, 07:16 AM

Quote:

Originally Posted by offroad

Would this normally be located on the frame close to the converter or near where shore power is connected?

Might be good to check this periodically.

It was directly under the converter at the frame.

The green wire went directly from the converter's ground buss to the frame (via a hole in the floor) and the Neutral from the converter's buss went to another Neutral buss screwed to the floor; and then to the frame via the same hole as the green ground wire.

Toby · 08-15-2014, 07:25 AM

Well...after reading that article, I now have two more gadgets to pack in my handy camping tool bag (both of which I already own but never thought to bring along).

bubbles · 08-15-2014, 08:11 AM

Just an observation. Looks like the ground point was not burnished (is still painted) and also appears that there is a star washer between terminal lug and ground point (a no-no). For proper bonding there should be no hardware between any stacked terminal lugs and bottom lug at bonding point. Additionally, the area beneath lugs should be burnished to expose bare metal and the J-BOX should also be correctly bonded.

**ependydad** · 08-15-2014, 08:50 AM

Quote:

Originally Posted by Herk7769

Doug, that WAS a "before" picture!

The corrosion was rust at the threads and under the bolt head.

Wow. It "looks" fine from the picture. I wouldn't have guessed.

**Herk7769** · 08-15-2014, 08:53 AM

Quote:

Originally Posted by bubbles

Just an observation. Looks like the ground point was not burnished (is still painted) and also appears that there is a star washer between terminal lug and ground point (a no-no). For proper bonding there should be no hardware between any stacked terminal lugs and bottom lug at bonding point. Additionally, the area beneath lugs should be burnished to expose bare metal and the J-BOX should also be correctly bonded.

What is the "J-Box"? "Junction Box"?

**Herk7769** · 08-15-2014, 09:15 AM

Just checked all circuits for reverse polarity and all outlets checked "Correct."

Brother Les · 08-15-2014, 09:24 AM

Subscribing.... I was sitting on the ground and installing scissor jacks.... getting a 'tingle' feeling from the frame..... Suggestions on how to find the short?

bubbles · 08-15-2014, 09:27 AM

Sorry for that. Yes junction box. But really meant that if the bonding for ground returns is not directly to the primary return item used (framing, etc.) but rather through any other means (box, tab, etc.) that bare metal to metal contact between the other means and primary return item should still be accomplished. "Floating Grounds" may cause great havoc with electrical circuits.

Pirogue · 08-15-2014, 09:27 AM

Very interesting thread.
I read an article recently where a little boy was killed by the "hot skin" condition. His dad plugged into the pedestal and the boy touch the door handle to go inside and was electrocuted. I started researching and came across the same No shock Zone website as linked in this thread. It's a very informative read and provides a simple inexpensive solution to mitigate the risk.
I also use a Frank's auto transformer and originally wondered if it offered protection from hot skin. After reading of Herks experience, it sounds like the answer might be maybe. Regardless I purchased a non-contact tester and it officially became a part of my set up routine this past weekend. Is it probable that this will happen? Who knows? But it absolutely is possible. I figured for 20 bucks and 20 seconds it's worth it to reduce any potential hazard. The alternative sucks.

**Herk7769** · 08-15-2014, 09:40 AM

Quote:

Originally Posted by Brother Les

Subscribing.... I was sitting on the ground and installing scissor jacks.... getting a 'tingle' feeling from the frame..... Suggestions on how to find the short?

Start with the article in Big Baron's post and then go to the ground/Neutral lugs from the converter.

One or the other should fix it.

**Herk7769** · 08-15-2014, 09:44 AM

Quote:

Originally Posted by Pirogue

I also use a Frank's auto transformer and originally wondered if it offered protection from hot skin. After reading of Herks experience, it sounds like the answer might be maybe.

The Franks will alert you to reverse polarity with the red light (Much like every other power monitor - Surge Guard, etc).

However, if the failure is on the "output" side (like a poorly bonded Neutral at the camper's frame), the power monitor will never "see" it.

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