"Hot Skin" with Fiberglass?

[Ruth C.]

Has someone already addressed the "Hot Skin" phenomena? This is scary, but I was wondering if FGRVs are exempt or does the frame acts as a conductor?
I wish I had asked questions in science class.

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[Mikmay]

I don't think that could ever happen in a fgrv especially if the floor is fg or wood . A lot of stick built trailers can conduct through the steel framing and aluminum skin but I have never heard it happening in fg trailers.

[steve dunham]

This is not a new phenomena. This was an issue with mobil homes for many years. When I went to trade school in the 60's we studied this. It is caused by improper equipment grounding / bonding of the trailer frame and metal parts. Since fiberglass is an insulator and the frame of your trailer is grounded when hooked up to 120 VAC , I would not be overly concerned.
Think of your trailer as a double insulated power tool.

[jaye580]

I got zapped once on my fiberglass RV - had it plugged into my shed and touched the tongue and zing. It only happened once so I figured it it was an improper ground in the shed.

[Dan Meyer]

When I was a kid, I had this happen to our family motorhome in a campground in Ensenada, Mexico. I knew just enough about electricity to fix the problem.

I don't think this could happen with a fiberglass RV, unless you touch the ground (grass, gravel, concrete; whatever is under your feet) and some metal part of the trailer while it has a 'hot ground'.

--Dan Meyer

[Bullington]

This is easy to check, get a clamp on style amp meter that will clamp around your power cord (all conductors). While power is supplied to the camper and appliances are "on", check for amp draw, should read "0". The way this works is if you have "x" draw on the "hot" wire, you should have "x" on the neutral that cancels it out. If you have a reading of anything but "0", this mean you are returning energy into the ground, not by way of the cord !! To help find it turn each load on individually and find the one that is causing it, then repair as needed !!

[steve dunham]

Your trailer is sitting on rubber tires so unless your metal stabilizers are in direct contact with the earth or your front jack has a metal base plate in direct contact with the earth , you can have potential to ground from the frame but you will not have current flow. If the trailer frame becomes energized and the trailer is floating , when you touch the frame you become the return path to ground. There has been several proposed changes to the code to require all the receptacles in RV pedestal's to be GFCI protected but they were not adopted . A simple continuity test between the trailer frame and the equipment grounding pin on the male cord cap would tell you if your trailer is grounded. There should be no continuity from the frame to the neutral and Line blades on the male cord cap.
Clamp on amp meters are not accurate enough to sense leakage down in the milli amp range . On low current loads we would loop the hot conductor several times and then read the load with a clamp on amp meter to get a more accurate reading.
A GFCI can sense a 5 milli amp leakage

[Bullington]

I beg to disagree with you, a good quality inductive, digital amp meter clamped onto the cord is what we use to detect this. I do it in marinas all the time and can detect losses. It seems the people that are members of this group are just too smart for me, almost every post I have made a comment or a suggestion to try to help someone, it gets an argument going. I feel I need to be somewhere else.

[steve dunham]

Originally Posted by Bullington

I beg to disagree with you, a good quality inductive, digital amp meter clamped onto the cord is what we use to detect this. I do it in marinas all the time and can detect losses.

My $300 amprobe digital clamp on amp meter would not .If the frame is energized and floating above ground there is no current flow to detect because there is no return path for current flow .
I can energize any piece of metal and if the metal is not grounded there is potential to ground but no current flow . Hook a hot wire directly to a metal Junction box and set the Junction box on an ungrounded surface , the box will be energized but there will be no current flow. Now grab the box in your left hand and take your right hand and grab a grounded object and tell me what happens .
You are confusing voltage potential with current flow. This is why I can grab a hot conductor while standing on a dry wooden floor and not get a shock. There is potential but no current flow
I have hooked up hot conductors ranging from 120 VAC to 480 VAC many times using bare hand and metal tools and not been shocked.

[Bullington]

Originally Posted by steve dunham

My $300 amprobe digital clamp on amp meter would not .If the frame is energized and floating above ground there is no current flow to detect because there is no return path for current flow .
I can energize any piece of metal and if the metal is not grounded there is potential to ground but no current flow . Hook a hot wire directly to a metal Junction box and set the Junction box on an ungrounded surface , the box will be energized but there will be no current flow. Now grab the box in your left hand and take your right hand and grab a grounded object and tell me what happens .
You are confusing potential with current flow. This is why I can grab a hot while standing on a dry wooden floor and not get a shock.
I have hooked up hot conductors ranging from 120 VAC to 480 VAC many times using bare hand and metal tools and not been shocked.

Did you read my first post? I said turn on the loads ! If there is no return path, the loads won't be "ON" and working !

[steve dunham]

Originally Posted by Bullington

Did you read my first post? I said turn on the loads ! If there is no return path, the loads won't be "ON" and working !

You are confusing the grounded conductor ( Neutral) with the equipment grounding conductor. The neutral is designed to be a current carrying conductor . The equipment grounding conductor is designed only to carry current when there is a leakage or fault.
I taught DC & AC theory at a Vocational College for over 30 years
so believe what you want. .I am finished trying to explain how electricity works to you !! We are just wasting the time and patience of other forum members

BEST WISHES
Steve D.

[Bullington]

Originally Posted by steve dunham

You are confusing the grounded conductor ( Neutral) with the equipment grounding conductor. The neutral is designed to be a current carrying conductor . The equipment grounding conductor is designed only to carry current when there is a leakage or fault.
I taught DC & AC theory at a Vocational College for over 30 years
so believe what you want. .I am finished trying to explain how electricity works to you !! We are just wasting the time and patience of other forum members

BEST WISHES
Steve D.

I'm not confusing anything. I know that the ground conductor, under normal circumstances does not and should not carry current. It is for safety, just in case an appliance goes to ground (makes it's case hot) and you touch it while touching a good ground. I pitty all those students you taught all those years

[k corbin]

Originally Posted by Bullington

I beg to disagree with you, a good quality inductive, digital amp meter clamped onto the cord is what we use to detect this. I do it in marinas all the time and can detect losses. It seems the people that are members of this group are just too smart for me, almost every post I have made a comment or a suggestion to try to help someone, it gets an argument going. I feel I need to be somewhere else.

Of course people are going to argue with you and have differences of opinion with each other too, that is simply the nature of internet forums where you literally have thousands of personalities sharing the same space. Too many cooks in the kitchen

[Mary F]

Simmer down, now. Remember to disagree without being disagreeable. (Thank you!)

So, has the OP's question been answered yet?

[Ruth C.]

Yes! I think my question was answered very thoroughly. Thank you everybody!


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[Bluetang99]

I still don't understand how the frame can be energized? For this to happen wouldn't a wire have to fall out of a receptacle then create a hole in the floor and touch the frame? I'm curious because I redid the electrical and didn't ground the frame due to the lack of reports of Scamp frames becoming energized. All I heard about this topic is better safe then sorry but that's about it.

[larryc]

Originally Posted by Bluetang99

I still don't understand how the frame can be energized? For this to happen wouldn't a wire have to fall out of a receptacle then create a hole in the floor and touch the frame? I'm curious because I redid the electrical and didn't ground the frame due to the lack of reports of Scamp frames becoming energized. All I heard about this topic is better safe then sorry but that's about it.

wouldn't plugging your trailers 120 into a ground fault protected outlet check for a bad ground? If there was one wouldn't the outlet trip?

[Dan Meyer]

Originally Posted by larryc

wouldn't plugging your trailers 120 into a ground fault protected outlet check for a bad ground? If there was one wouldn't the outlet trip?

The 30 amp outlets most campers use, including most of our Scamps, don't have GFI's.

If everything is wired properly and all of the connections are in good condition, you won't get a hot frame. Also, a GFI can be mis-wired in such a way that it will not provide any protection.

We don't live in a perfect world. Be careful out there.

--Dan Meyer

[Raz]

Originally Posted by Bluetang99

I still don't understand how the frame can be energized? For this to happen wouldn't a wire have to fall out of a receptacle then create a hole in the floor and touch the frame? I'm curious because I redid the electrical and didn't ground the frame due to the lack of reports of Scamp frames becoming energized. All I heard about this topic is better safe then sorry but that's about it.

The best argument I can give to grounding your frame is that it protects you and your family from harm. With a grounded frame any fault will activate the protection device; breaker or fuse. A far better outcome than trying to find the fault you didn't think could happen after someone has been hurt. Just a thought. Raz

[Jon Vermilye]

Originally Posted by Bluetang99

I still don't understand how the frame can be energized? For this to happen wouldn't a wire have to fall out of a receptacle then create a hole in the floor and touch the frame? I'm curious because I redid the electrical and didn't ground the frame due to the lack of reports of Scamp frames becoming energized. All I heard about this topic is better safe then sorry but that's about it.

Code & safe practices require that the trailer frame be connected to the AC ground. Any high current fault to the frame will trip the circuit's breaker & low current faults will be less likely to shock a user who is between the frame & the earth. Just as important is that the neutral (the grounded conductor or white wire) IS NOT connected to ground or the trailer frame in the trailer.

A couple of examples of where faults that energize the trailer frame can happen:

The water heater electric element fails, allowing a connection between it & the water. While distilled water is an insulator, real water is pretty conductive. Any water in the trailer & metal fittings could become "live".

The 120V electric element in the refer fails, allowing a connection between it & the frame of the refrigerator. The propane connection to the refrigerator is usually conductive (copper tubing) which is often touching the trailer frame.

A fault in the converter that places 120V line voltage on the 12V system. Since the 12V system is often connected to the frame, this could put the frame at line voltage. (To help prevent some converter fault problems, NEC requires that there be a bond (electrical connection) between the converter case & the trailer frame).

I have experienced all these examples (although not always in fiberglass trailers) during my many years of electrical troubleshooting. Multiple faults in appliances, broken wires, etc can often combine in ways that are unexpected - a grounded frame (and, obviously, a good ground connection between the trailer & the AC service) is a critical safety factor.