By Mike Sokol
Dear Readers,
We’re going to take a one-week break from my expanded series on troubleshooting short circuits to give you some feedback from my RVelectricity seminar at the Boston RV Expo last weekend.
While I covered everything from campground pedestal measurements to using digital meters to surge protector selection and operation, the demonstration that got the most comments during and after the seminar was showing how to detect a hot-skin condition using a Non-Contact Voltage Tester. And yes, it starred my tiny Volkswagen micro/micro bus and Flash (the action figure). So here’s a brief recap of what hot-skin voltage is, what causes it, and how to test for it with a simple $15 tester you can buy in any big box store or on Amazon.
Quite simply, any time the chassis (and skin) of your RV is electrically charged to more than a few volts above earth ground, it can create what’s called a hot-skin/contact-voltage condition. And when that occurs, if you’re standing on wet ground outside of the RV and touch anything metal (such as a door handle, hitch or even the tow vehicle), your body can complete the electrical circuit which allows current to flow through your body.
Now, contrary to what you’ve seen on television or the movies, touching 120 volts AC generally won’t produce a big blue glow, or sparks or any other pyrotechnics. It simply sends anywhere from 10 mA (10 milli-amperes or 0.010 amps) to 100 mA (0.100 amps) of current though your body. And only 10 mA to 30 mA of current through your heart can put it into fibrillation which can result in death within 5 minutes or so without emergency intervention. Note that this is about the same amount of current required to run even this tiny 2-watt night light bulb at 120 volts (16 mA or 0.016 amps). So there really are no big sparks or glowing lights surrounding your body if you touch a hot-skin RV, but your heart can certainly be put into danger.
The one demonstration I did at the Boston RV show that got a lot of attention was my desktop hot-skin demonstration where I charge up the chassis and skin of a small RV model with up to 120-volts AC, then show how you can test for it with a $15 Non-Contact Voltage Tester. I really got a lot of questions about that demonstration during my RVelectricity seminar, as well as out in the hallway where I answered questions for the next hour. Click on the screen shot (“People like Mike!”) to see what one of my attendees said about my seminar.
I was demonstrating how to test for an RV hot-skin/contact-voltage with something called a Non-Contact Voltage Tester, which is basically a pen-sized device that will detect a voltage potential of more than around 40 volts AC on an RV skin or chassis. And that’s even for NCVTs that are rated from 90 or 100 to 1,000 volts. Their low-voltage range is only applicable when they’re testing a small object like an extension cord. But put an RV in front of them with hundreds of square feet of surface area, and these NCVT pens will beep and buzz with an RV hot skin as little as 40 volts, and from 1 to 2 feet away if the RV has a hot-skin of 120 volts. Click the picture to watch my short video on the test procedure with a variety of different brand and model Non-Contact Voltage Testers that I use and recommend.
If you want to read more about what causes hot-skin voltage on an RV, then I’ve got you covered there as well. At the end of this paragraph is a link to one of my advanced articles on the various causes of low-, medium- and high-current hot-skin/stray-voltage conditions, as well as a few troubleshooting methods. But remember, just because you have a low-current hot-skin condition today that may only tingle you a bit, it can turn into a medium- or high-current hot-skin condition in a heartbeat (literally!). So please take all hot-skin/contact-voltage conditions seriously. Read all about it HERE.
And let’s not forget Flash, the action figure. Yes, he only has a flash bulb for a brain so there’s not a lot of smarts there. But Flash has faithfully showed us all dozens of times what happens if you’re standing on the wet ground and touch any energized metal surface on your RV. In his case he blows his top (actually ignites a flash bulb), but in your case that could be your heart going into fibrillation.
So please get yourself a Non-Contact Voltage Tester, and always check your RV for a hot-skin/contact-voltage condition any time you plug into shore power. And never accept feeling a shock from an RV (or any electrical appliance) as normal. When that happens it’s a hint that the next shock could electrocute you or a loved one, and that’s a totally preventable tragedy if you simply pay attention and don’t accept shocks.
Next week we’ll resume my new series on 120-volt AC short-circuit troubleshooting. Until then, let’s play safe out there….
Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.
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Mike – with a predominately fiberglass motorhome (Winnebago Minnie Winnie) can hot skin condition be tested successfully with NCVT or will your procedure for metering using something metal like stairs be the only effective approach ?
If you have an all-fiberglass egg, then you just want to point the NCVT at the metal steps or even the trailer hitch. But since nearly everything metal on an RV is bonded to the frame, and the frame is really what’s being energized, most anything metal you point at will suffice.
Mike, I use a Progressive surge protector and I am wondering if it’s worthwhile to use my non contact voltage tester at the pedestal before I plug in the surge protector?
Interestingly, I’ve found a few pedestals where the metal box itself was electrically energized with a hot-skin voltage. So testing with a NCVT first is probably a good idea, especially if the pedestal box looks old and beat up.