By Mike Sokol
Spring is here, and with it I’ve received a bunch of emails and postings on my RVelectricity Facebook page about readers feeling a shock from their RV while plugged into home power using a dogbone adapter or a campground pedestal. There are a lot of guesses and wrong information floating around the internet and social media platforms, so I’m going to clarify what a hot-skin is here.
DANGER: If you feel any kind of shock while touching your RV and standing on the ground, immediately disconnect your RV from shore power and read below. This is potentially a very dangerous situation.
What is a hot-skin?
Hot-skin is a term long in use by the RV industry for decades before I started writing my No~Shock~Zone and RVelectricity articles. Basically it’s anytime you feel a shock while touching any part of your RV while standing on damp ground.
Is it dangerous?
Yes, it certainly can be. There are a lot of variables involved. But once the voltage potential on the skin and chassis of your RV reaches around 30-volts AC, and if the ground you’re standing on is damp, you can feel a shock. Depending on how much fault current is available and how wet the ground is, this can be anything from a mild tingle to a huge shock that can put your heart into fibrillation, which can be deadly.
What doesn’t cause it?
But that’s simply not true. All RV electrical systems have their neutral and ground conductors isolated from each other. So reversing them doesn’t cause a hot-skin voltage on your RV chassis. For that to occur you must have a broken or missing ground wire (Equipment Grounding Conductor) between your RV chassis and the main service panel that feeds power to your house or campground.
What does cause a hot-skin condition?
Well, two things cause a hot-skin condition. The most important one is the ground wire – sometimes called safety ground and officially called the Equipment Grounding Conductor or EGC in the National Electrical Code book. For a hot-skin voltage to occur you need to have lost your Safety Ground connection. This is the ground pin or lug on your shore power connection. It’s the contact at the top of any 30- or 50-amp plug.
Next you need to have a source of ground fault current. That can be anything from the normal 2 or 3 mA (milliamps or 0.002 amperes) of leakage currents in your RV, up to a 20 or 30 amperes of available fault current if a wire was pinched or a screw driven through it inside of a wall.
Will a ground rod stop a hot-skin?
No, it will not. A grounding rod’s main duty is to provide a path for nearby lightning strikes to go deep into the dirt before they side-flash and damage more electrical gear. And they are only required to exist at the service panel, not the campground pedestal and certainly not connected directly to your RV.
How do I troubleshoot a hot-skin voltage?
First you need a basic 3-meter kit from Southwire or Klein which you can get HERE. The initial test should be verifying you have a hot-skin voltage on your RV.
The easiest way is to use a Non-Contact Voltage Tester like this one available from Amazon HERE. Simply power it on, test it on a powered outlet to make sure it’s actually working, then touch anything metal on your RV with the tip of the probe. If it lights up and beeps when you make contact, then your RV has a hot-skin around 40 volts AC. If it beeps from several inches away, then your RV hot-skin is around 80 volts AC. And if it beeps from 1 to 2 feet away, then you have a very dangerous 120-volt hot-skin condition.
How do you find the problem?
Once you’ve confirmed a hot-skin voltage on your RV, you need to find why you have a lost ground wire. The best way to begin is to check the electrical outlet you’re plugged into for proper ground and/or polarity. Use a simple 3-light cube tester on the outlet which you can get from Lowe’s or HERE, and if you’re plugged into a 30-amp outlet you can use a 30-to 15-amp adapter. Read more and watch my video on how that works HERE.
Yes, I said polarity when I already told you it won’t cause a hot-skin voltage. But it does suggest that whoever wired an outlet with reversed polarity didn’t do something else properly. If you do get an open ground indication, you’ll want to get a technician or electrician to correct the problem. And no, just adding a ground rod does not fix it. They need to make sure the ground wire is bonded back to the service panel’s neutral bus.
Look for an extension cord and dogbones with broken grounds
A surprising number of hot-skins are caused by using an extension cord with a lost or broken ground pin, or an adapter with a ground that’s broken internally. So replace that cord or adapter immediately and retest. If you still have a hot-skin voltage then you haven’t identified the actual problem. But it’s possible to have several things wrong at the same time.
Go ahead and plug your 15-amp adapter into a standard GFCI outlet on your house. If the GFCI outlet trips, then you must have more than 5mA of ground fault current. That suggests something else is wrong inside of your RV electrical that’s creating excessive fault current and needs to be corrected. I’ll be adding a list of possible ground-fault sources to the bottom of this article soon.
If your RV doesn’t trip the GFCI after you’ve corrected the broken ground connection, then your hot-skin voltage was caused by a low-level fault current that is now being properly mitigated by the ground conductor. So all is well, and you stopped the hot-skin voltage by repairing your broken ground connection.
Don’t accept a shock as normal!
Never leave an RV unattended that’s shocking you. You’ll want to unplug it from shore power immediately and repair the problem. Here are a couple more articles I’ve written about the inner workings of hot-skin troubleshooting that are worth reading.
By popular request I’ll be adding a few advanced hot-skin troubleshooting techniques here later tonight. So come back tomorrow and learn more about the various sources of fault current that can cause a hot-skin voltage if your ground conductor is broken. See you later.
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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