Stray Voltage?

YC 1 wrote:
Lots of information on this issue. It is very common and can be very dangerous.

Click the link above.

I'm Mike Sokol from The No~Shock~Zone. Thanks for posting links to my RV Electrical Safety articles above. Let's get right to the main point of his thread and work backwards. First off, if you ever feel or measure any voltage (more than 2 or 3 volts) on the skin/chassis of an RV that's a sure sign that the electrical ground has failed. We call this the EGC (Equipment Grounding Conductor) in the code books, or more commonly just the Safety Ground. It consists of a low resistance connection (less than 1 ohms) from the frame of your RV, through your shore power cord, any dog-bone adapters and extension cords, through the campground pedestal or home outlet, and finally back to the electrical service panel's G-N-E (Ground-Neutral-Earth) bonding point. That's where the ground rod is connected to the electrical system. A EGC ground failure can be ANYWHERE in this rather long connection.

If you have a proper EGC connection back to a real bonded ground, then it should be impossible to have more than a few volts measured between the frame/skin of your RV and an earth ground test point. However, note that adding a ground rod next to your RV does virtually NOTHING to actually "ground" your RV. The confusion is that the same word "ground" is used for a lot of different things in the electrical business, many of which have nothing to do with earth ground.

A failed EGC Ground by itself won't cause a voltage on your RV skin, but practically any plugged-in appliance in your RV will leak at least some current to its chassis. This is usually only a few mA (milli-amps) which isn't immediately deadly. Sometimes called a ghost voltage, it is indeed a real voltage, but at such low current that sometimes even measuring it will make it go away. But it does show you that your EGC Ground has failed, and your RV is only an heartbeat away from electrocuting someone if there's a ground fault failure with more current potential. This can be caused by a screw being driven through a power wire in the wall, an extension cord with worn through insulating contacting the chassis or your RV, or even an appliance or inverter with a failed transformer or filter capacitors. So if you ever feel or measure voltage between the body/frame of your RV and the wet ground, unplug from shore power immediately and sort out the grounds.

So what are the typical EGC ground failures? Most of the time it's something silly like an extension cord or dog-bone adapter with a broken or missing ground pin. But it can just as easily be a broken or loose connection in the campground pedestal itself. And I get emails every week from someone plugging into a friends broken or mis-wired garage outlet, then feeling a shock on the RV. So it's a dangerous problem that shouldn't be ignored.

You can test for hot-skin conditions using a simple procedure I developed which I call a proximity hot-skin test using a Non Contact Voltage Tester (NCVT) available in any big-box store or online. See my article on hot-skin testing at http://www.noshockzone.org/rv-electrical-safety-part-iv-%E2%80%93-hot-skin/ and a video on hot-skin testing a 40-ft toyhauler at https://www.youtube.com/watch?v=Y8h64X33aKg

In any event, please test for the problem and fix this immediately as this weekend is the one year anniversary of me covering the death of the 3-year old boy last year who was electrocuted from a hot-skin condition on his family's RV trailer in the backyard. See my report on that tragedy here: https://www.youtube.com/watch?v=opuult8jMOo

Let's play safe out there...

Mike Sokol
No~Shock~Zone

And feel free to post any questions about RV electrical hookups and safety here. But make sure you alert me since I'm on dozens of forums and don't troll for questions. I typically only find that I'm on a thread when someone links to my blog.