Reflected Hot Skin Voltage at a campground….
A question from yesterday's article on RV grounding
Everyone,
Here’s an interesting comment and question from yesterday’s article on RV grounding. You can reread it HERE.
Hey Mike,
About Ground and hot skin: If I understand what I’ve read, hot skin requires two things: a current leak to chassis/ground/skin and an improper or missing ground.
I’m trying to reconcile the above with a condition I ran into a campground. Underneath a TT roll up against the axle, I’m covered in sweat, ground is damp and I feel an electric tingle. Start to try to find the problem when a neighbor walks over and says every RV in the area has a low level of hot skin. Shoved one probe of the voltmeter in the dirt and touched the frame with the other probe. Did this on five or six RVs all showed 10 to 12 volts.
Any thoughts? - Colan A
Hey Colan A,
There’s two possibilities. First, it’s possible that the power company has an current imbalance in their 3-phase distribution system which can create a substantial voltage on their local grounding conductors. I’ve personally measured as much as 5 volts on the incoming ground from the power company, but 10 or 12 volts AC would be possible. I’ll write an in-depth article on this topic soon.
However, I believe what you encountered was something I’ve named a Reflected Hot Skin Voltage. Please read this article below and let me know if you have any questions. Find the direct link to the article HERE.
Let’s play safe out there… Mike
They don’t measure the ground voltage at all and will keep supplying power. And there’s enough nuisance GFCI tripping already. The hope is that GMI (Ground Monitor Interrupter) will help.
Most of our RV’s today have GFCI that protects several receptacles in our RV. How do these GFCI behave when there is a deadly Hot Skin voltage (30V or higher) on an RV? Do the trip? Giving an indication something electrical is at fault? Or do they just happily keep supplying electrical power on all the receptacles they are protecting? Clearly, they should trip on a current imbalance of the circuit they are protecting. But what about out-of-balance current coming into the RV where the ground has a deadly voltage already applied?
And maybe electric hot water heaters should be protected by a GFCI to prevent some hot skin conditions where RV park electrical ground maintenance is lacking and heating elements fail.