Have you ever heard of "hot skin"?
No, it's not the result of an Airstream sitting in full sun. It's a dangerous (potentially fatal) situation that can happen with RVs.
Hot skin means that the exterior, frame, and other metal parts of your RV have become electrically energized. In other words, your RV can give you a big shock when you touch it and the ground at the same time.
It doesn't only affect aluminum-bodied Airstreams. Hot skin can happen to any brand of RV.
What causes hot skin?
This condition is only possible when two things both happen:
-
The RV is plugged in and the electrical connection to ground is absent. This can be the result of a mis-wired power pedestal or sub-panel, damaged power adapter, extension cord, power cord, or a broken ground connection in the RV.
This is why you never plug an RV into a 2-prong power outlet. The ground plug must always be connected, for safety.
- Something in the RV is leaking current. This is often the result of a burned-up water heater element, but it can be almost anywhere in the RV, including chafed wires in the RV or an appliance.
The wrong way to find out that you've got hot skin is by feeling a "tingle" when entering or exiting your RV, perhaps on a day when the grass is wet. You would feel that tingle (or worse) because you are momentarily the connection between the ground and the RV.
This tingle is super-dangerous. It doesn't take a lot of power to throw a human heart into irregular heart rhythm. Just 60 milliamps (at 120 volts) can do it. So if you ever feel a tingle when entering or exiting – or perhaps when touching the side of the doorway – immediately unplug the RV and don't plug it in again until the problem has been fixed.
An easy safety check
One right way to check for hot skin is with this cheap safety tool: a Non-Contact Voltage Tester (NCVT). You can get one for as little as $20 at most hardware stores. Look for one that can detect all the way down to 12 volts, like the one pictured:
All you have to do is touch the tip of the NCVT to a metal part on the RV's exterior, when the RV is plugged into power. It doesn't matter whether you're plugged into 15-amp, 30-amp, or 50-amp power.
If the NCVT detects stray voltage in the RV, it will warn you with a light and/or a beep.
Anything that lights up the NCVT should be investigated. Note that the absence of a warning from an NCVT is not a guarantee that there's no voltage, but if it alarms, there is definitely something going on.
You can see how the NCVT works by putting it near the power cord or power outlet while the RV is plugged in. It should light up because it is detecting the normal AC power in those areas.
What to do if you find a problem
First, unplug the RV.
Second, don't use the inverter. You don't want any source of 120 volt AC power around when there's a suspected hot skin problem.
Third, because finding the cause of hot skin is complicated, for most people the best next step is to take the rig to a good service center or mobile RV electrician. Both the reason for the failed ground and the source of the current leakage must be found. If you want to do a deep dive into the process, check out Mike Sokol's blog.
Will my EMS or power tester help?
Yes, and no.
True, an inexpensive power outlet tester or a full-blown Progressive Electrical Management System will tell you if the campground power outlet has an "open" ground. That's definitely a leg up in safety.
But unfortunately these testers can't detect bad ground wiring inside the RV or in the power cords. It takes a trained person with the proper meter to do that.
Power outlet testers also can't tell you if you have hot skin. For that, you need the NCVT. That's why I believe this is a cheap safety tool more RV owners should carry.
Rally safety checks
A few major rallies I've attended have deployed safety volunteers with NCVTs to check every RV for possible hot skin problems. If you're a rally organizer and your event offers electrical hookups, you might having some folks do this test after the rigs are all plugged in. It takes only seconds to perform the test.
And if you're organizing a maintenance rally, you could consider spreading the word about this issue by adding a demonstration of how to check for hot skin to the seminar schedule.
8 comments
Michael Carden
Wow! I had never heard of “hot skin”. I just ordered the exact tester you have from Home Depot for less than $20. Thanks for the heads up. I assume we should make this part of our setup process after shore power has been connected.
Mike
This is crazy great! Last time I went out was the first time I ever felt it and thought it was strange. I wrote it of because I have an EMS and figured it must be ok. Then I read someone else having the same problem on a Facebook site. Then you pop up as usual with a great answer, thank you!!!
Lorraine Paul
Great info
Thank you.
I am signing my husband up for your newsletter.
Bernadette Strange
Doesn’t my surge protector detect grounding errors? I always plug this in first to test the pedestal.
Corey
So since an electric heater element or other internal wiring fault can basically happen at any time, without warning, is the suggestion here that you should test the exterior of your airstream with a NCVT prior to each time you enter the trailer or make physical contact with the exterior? This seems quite impractical. It seems like there could be a box with audible and/or led indicators that could mount up by the propane box and connect to the frame or skin that could notify users of a “hot skin” scenario.
Charles Jensen
When my RV (not an Airstream) was constructed the walls were placed onto the frame. During the process, the main power supply wire was pinched. Overtime the wire bared, energizing the metal exterior. After experiencing a few minor electrical shocks, the wire finally separated and the power to the trailer failed to function.
Rich Luhr
Corey, we’re not suggesting that the RV needs to be tested at every overnight stop. Instead, perhaps test once or twice a year, or whenever you suspect there might be a problem.
I like your idea of a built-in product that detects hot skin. Hmmmm….
Rich Luhr
Bernadette: Your surge protector (or any inexpensive plug-in electrical tester) will detect a ground fault in the campground wiring, but it won’t be able to detect a ground fault inside the RV unless you plug it into every outlet.
Since a ground fault inside the RV can also contribute to “hot skin”, it’s not enough to just test the campground power pedestal—although it’s still a very good idea.