Hi Mike,
I got shocked by my coach yesterday. An electrician came out and said the pedestal was good. When I shut off the rear air conditioner in my RV the problem went away. I had a surge protector hooked up, but found out it was bad so it didn’t work. I still believe the campground pedestal was bad but the electrician doesn’t really know how to test it. My question is why didn’t my coach smart system shut everything down and would a good surge protector at the pedestal prevent this from happening again? —Mark Whitford
Hey Mark,
Good that you’re concerned about feeling a shock. Many of the consumer electrocution deaths I’ve studied started with a series of mild shocks that they ignored for days or even weeks. Then when the “right” set of circumstances occurred, they or a family member were injured or killed. What’s likely happening is two separate issues that added together create a hazardous shock condition. For a more detailed description of the measuring techniques and nomenclature I’m using, here’s an article I wrote for RV Education 101 a few years ago.
Here’s a link to the full article, RV hot-skin voltage, where you can zoom in to read it.
LOST GROUNDS
First, for any sort of hot-skin voltage/shock to occur you need to have a compromised ground wire connection somewhere between the chassis of your RV and the campground’s main electrical service panel’s Ground-Neutral bonding point. Yes, that’s the main circuit breaker panel that connects the campground to the incoming electrical pole from the power company. This can be caused by a broken wire, loose connection or corrosion anywhere on this path, which can be hundreds to even a thousand feet long, depending on the size of the campground. Note that I am NOT talking about a ground rod in the dirt, which really has nothing to do with grounding your RV. So starting at your RV and working upstream you need to confirm the following safety ground connections:
- Chassis ground bonding screw in your RV’s circuit breaker panel is tight
- Ground connection in the shore power connector on the side of the RV is OK
- Green ground wire in your shore power inlet on the side of your RV is connected
- End-to-end Ground continuity in your shore power cable
- Continuity of the ground wire and contacts in any dog-leg adapter you’re using
- Can’t be any corrosion or loose screws in the campsite pedestal including the receptacles, grounding bus, or connection back to the main service panel
- No broken ground wires between your campsite pedestal and the campground’s main service panel
Wow! That’s seems like a lot of testing, but it can all be confirmed in a few seconds using a Ground Loop Impedance Tester such as the Ideal SureTest Circuit Analyzer. They work by putting a very short (1/60 of a second) pulse between the hot wire and ground wire, then measure to see how well the ground wire can get rid of this fault current. You get a reading in ohms, with 1 ohm being the maximum value accepted to pass electrical code. Yes, these testers cost $300 or more, but I believe that every campground and RV technician should have one and know how to use it, and all campgrounds should test their pedestals for EGC ground continuity at least once a season.
FAULT CURRENTS
Secondly, for a shock to occur you need a source of fault current. In the article above I detail low-, mid- and high-current shocks. You probably have low-current hot-to-ground leakage in the rear air conditioner. Most of the time that’s nothing to worry about. That’s because everything leaks at least a little AC current to the chassis-ground, and that’s normally drained to ground harmlessly via the EGC grounding wire in your RV. But if that safety ground wire is compromised anywhere between the chassis of your RV and the campground electrical service panel, then you could feel a shock.
SMART PROTECTORS
As far as a surge protector preventing this from happening again, a standard MOV-based “surge protector” will do nothing to shut down the power to your RV due to a lost ground connection. You need to get a Smart Surge Protector of some sort with a computer-based voltage monitoring system and internal relay that shuts off AC power to your RV if the incoming voltage from the pedestal is too high, too low or the ground from the pedestal has failed. However, simple devices like this can’t protect you from an RV with a failed ground connection inside of its own circuit breaker panel. That’s because grounding failures downstream of these plug-in surge protectors can’t be monitored.
FUTURE SHOCK
I’m writing a future article about the differences between the various MOV-based Surge Protectors and Smart Monitoring Systems from Progressive, TRC and others. In it I’ll discuss which models will disconnect your RV from shore power if the pedestal voltage gets too high, too low, or loses its ground. And there are a few other features that I feel are really important. Stay tuned for Part II of this article in a later column. To the above-right is a picture of a Surge Guard Protector, which does indeed monitor the voltage and disconnect your RV from shore power if something goes wrong.
SAFETY FIRST
Don’t get complacent just because it felt like a little shock the last time. Any sort of electrical shock is an indication of a failed chassis ground on your RV, which can turn into a killer electrocution shock at any time. So take any electrical shock seriously, no matter how mild it feels at first.
Let’s play safe out there….
Mike Sokol
Mike Sokol is an electrical and professional sound expert with 40 years in the industry. Visit NoShockZone.org for more electrical safety tips. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.
##RVT814
