How to Discover Source of Hot Skin

My trailer is parked under a metal carport on a dirt pad covered with rock. It has been raining and the ground under the rock is damp or wet, depending on where you are under the carport. Last evening, I was laying on my back on the rock, poking around the trailer skirting and I felt an electrical tingle where my arm was touching the metal trailer skirting. I had never noticed any problem like this in the past, not to say it didn't exist, but I had never experienced it. Got out my circuit tester, the plug-in type with the lights, and start testing the receptacles in the trailer, the extension cord from the garage to the trailer, and the garage. Everything tests 'fine'. The trailer has a hard wired surge protector, Surge Guard brand, and the indicator that there might be a problem on the protector is not lit up. I also have an Electracheck monitor to alert me to problems, bot nothing detected there either. Immediately disconnected from shore power.

This morning, I plugged in the trailer to shore power after verifying that the male end of the shore power cord was wired correctly. I get out the multi-meter and test for AC voltage between the trailer skirting and placed the ground-side tester probe into ground (mud under the rock) and I get a reading of .245 volts. When the ground point is changed to the carport supports which have metal rebar driven into the ground about 3 ft, reading rises slightly to .260 volts AC. Checking with extension cord un-plugged, reading was .130V AC. (Definitely didn't expect to see that.) Did a recheck of all the receptacles with the light-type circuit tester and everything tests OK. Turned off battery switch - no change.

What is the problem here? I wouldn't think you would feel about 1/4 of a volt, but I did, at least when the ground is damp. How could there be AC Voltage (as small as it is) when the trailer is not plugged into shore power? Where to start? How does one figure this thing out?

25 Replies

Salvo
Explorer
Aug 20, 2015
I can't believe I'm responding to this nonsense!

You're missing basic electricity theory! Let me school you. The 12V battery is isolated from earth ground. There will never, ever be a current between the isolated battery within a trailer and earth ground.

MEXICOWANDERER wrote:
Señor I may be at a disadvantage because even a single flashlight battery will rudely tingle the skin on the inside of my forearm when the skin is damp. Not a slight tingle either. The human body is weird. Not all individuals are built the same.
MrWizard
Moderator
Aug 20, 2015
you have a reading when unplugged
then it is some kind of induction, RF, underground utility etc..
the only way to eliminate this is grounding the RV to earth ground
and this is NOT a 3ft stake in dry ground, or posts set in concrete
this is an 8ft ground rod into earth where it stays damp

Ron Nielson wrote:
MrWizard wrote:
check the electric ground to earth potential at the outlet the 5vr is plugged into

you might find zero volts
if so your situation is as stated in a previous post
capacitance effect, long cord, wires in rv, rv isolated from earth ground

My electrical problem occurs whether the trailer is attached to shore power or not. Is it possible that the extension cord or the outlet is the problem? I would not think so, but then I'm an electrical novice so my vote doesn't count for much.

Just makes sense to me that if there is electricity on the trailer skin, and the trailer is NOT attached in any way to shore power, then there's nothing on the shore power side of the house causing the problem.
MEXICOWANDERER
Explorer
Aug 20, 2015
Señor I may be at a disadvantage because even a single flashlight battery will rudely tingle the skin on the inside of my forearm when the skin is damp. Not a slight tingle either. The human body is weird. Not all individuals are built the same.

But, I heartily agree with your source of origin diagnosis. Correctly earth grounding the RV will result on 0.00 volts when disconnected or connected.

Place a spiral of magnet wire beneath a high tension power line and two things will happen. The coil of wire will develop a surprising amount of electrical power and secondly if discovered, the utility will indeed criminally prosecute for theft of electricity.
Salvo
Explorer
Aug 20, 2015
Again, if nothing is connected to trailer (with inverter off), and you are measuring a small ac voltage then it's coming from radio waves. The closer you're to a transmitter, the greater the voltage.

I measure about 0.1Vac from chassis to ground on my rv. This is normal!

You won't get any tingle from that though.

Ron Nielson wrote:

My electrical problem occurs whether the trailer is attached to shore power or not.
MEXICOWANDERER
Explorer
Aug 20, 2015
Something is amiss with drinking water passing through a length of PPE hose carrying 2-volts. The ultimate potentials would have to be enormous or mississippi river mud would have to be involved. It is standard practice to water washdown 12.5 KV distribution insulators with a stream of high pressure water.

Moot points all of this if the RV chassis is actually earth grounded. Course not eveeyone got an A in Pound-A-Peg. Mt stake is U-shaped, fluorescent red and I carry a D handle puller for yanking the stake out in seconds. All re-bar.
Ron_Nielson
Explorer
Aug 20, 2015
MrWizard wrote:
check the electric ground to earth potential at the outlet the 5vr is plugged into

you might find zero volts
if so your situation is as stated in a previous post
capacitance effect, long cord, wires in rv, rv isolated from earth ground

My electrical problem occurs whether the trailer is attached to shore power or not. Is it possible that the extension cord or the outlet is the problem? I would not think so, but then I'm an electrical novice so my vote doesn't count for much.

Just makes sense to me that if there is electricity on the trailer skin, and the trailer is NOT attached in any way to shore power, then there's nothing on the shore power side of the house causing the problem.
Ron_Nielson
Explorer
Aug 20, 2015
rekoj71

Great information about the problem you had (I NEVER would have guessed what your problem was found to be) and many thanks for the link. I'm working my way thru the posts now.

You asked about water piping to the trailer; no water going to the trailer at all.
MrWizard
Moderator
Aug 20, 2015
check the electric ground to earth potential at the outlet the 5vr is plugged into

you might find zero volts
if so your situation is as stated in a previous post
capacitance effect, long cord, wires in rv, rv isolated from earth ground
MrWizard
Moderator
Aug 20, 2015
so the 5vr is isolated from physical ground and electrically touching the earth
so any voltage potential between the ground wire in the cord (which is supposed to be at earth ground potential) which connects to the skin via frame ground at the breaker panel
is available between skin and earth
Ron_Nielson
Explorer
Aug 20, 2015
Harvard wrote:
Can we assume the voltage from the RV chassis to earth is the same as the RV chassis to the car port?

There is some difference in the readings between the earth/dirt/mud under the trailer on the one hand and the carport vertical structures (2 1/4" square tubing, mounted on concrete piers sunk 4' into the ground). The readings to the carport are higher.

Harvard wrote:

Also, is the RV tongue jack making a conductive path from the RV chassis to earth or is it sitting on a non conductor?

The 5th wheel landing legs and also the rear stabilizers rest on 13" tall wooden guard rail timbers, then on concrete block on top of the rock which covers the entire carport and approach area. So very little conductive capacity there.

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How to Discover Source of Hot Skin

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