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Sunday, July 1, 2001

Friends of Gary - Mike

Failures in Outlet Testing
By Mike Sokol

I’ve done it…. You’ve done it… We’ve all done it…. plugged a simple 3-light tester into a home or campsite outlet and declared it safe. After all, these $5 testers are everywhere. And you can see from the diagram on top that if you get two amber lights and no red light, the outlet must be wired correctly.  That’s WRONG!! Possibly DEAD WRONG!!! And here’s why. 

A few months ago I was experimenting with electrical grounds and contemplating just how 3-light testers work. So I downloaded a schematic and took one apart. As I drew the diagram I noticed something very odd about its operation. While the 3-light tester would be able to identify many circuit problems such as a missing Ground or swapped Hot and Neutral wires,  there didn’t seem to be any way for it to identify a situation where the Ground and Neutral were both at 120 volts and the Hot wire was at ground. How does this error occur? Let’s say you have ungrounded power outlets in your home, office, or campsite that never had a safety ground wire originally. This was common in pre 1970’s wiring so it’s often found in old buildings. You want “grounded” outlets, so you pay an electrician to replace the old “ungrounded” outlets with new “grounded” outlets.

So far so good, but what to do with that green ground screw when there’s no ground wire in the cable. Well, many electricians would perform something called a Bootleg (or False) Ground. They ran a jumper wire from the Neutral to the Ground screw, and tested it with a 3-light tester. If the tester showed two amber lights and no red light, the outlet was deemed safe. While against the National Electrical Code, this quick fix has been done millions of times in America. See diagram below.

While apparently safe, there’s one BIG danger with Bootleg Grounds. If the two power wires coming into the outlet box are accidentally reversed (Black and White wires swapped), then the outlet’s Ground and Neutral contacts are sitting at 120 volts while the Hot contact is at ground. This creates what I call an RPBG (Reverse Polarity Bootleg Ground) outlet. You  might think that such crazy wiring won't work at all. But it does operate normally, so normally in fact, that you might never know the outlet was a serious shock hazard. However,  your appliance or vehicle now has a potentially lethal Hot-Skin Condition. See this web page for a review.

So let's make this perfectly clear. There is no currently manufactured 3-light outlet testers that will identify an RPBG outlet. Even a $300 Ground Loop Impedance Tester such as an Amprobe INSP-3 or Ideal SureTest will NOT find an RPBG. They'll all report that the outlet polarity is OK, when the entire outlet's polarity is reversed. Even using a voltmeter between H-N, H-G and N-G will NOT find an RPBG outlet. 

How to test for RPBG outlets? Well a  Fluke VoltAlert (or other non-contact AC tester) can be used in conjunction with a 3-light outlet tester to identify a rogue RPBG outlet. It's as simple as poking the non-contact tester at the outlet contacts and making sure it doesn't light up on the ground or neutral contacts. 

(To see a demonstration video of what Mike is talking about, check out his video here! This should be required viewing by every RVer! Gary)

What to do if you find an RPBG outlet? DO NOT plug anything into it until you have the outlet tested and repaired by a qualified electrician. Tape over the front of the outlet with electrical tape (I prefer white tape) and mark it as "Hot Ground" so that nobody uses it until it's repaired. If you happen to plug your refrigerator, toaster oven, or RV shore power cord into an RPBG outlet, it will now have a hot-skin condition, which as you should know from my RVtravel.com and NoShockZone.org articles is when the entire RV or appliance body is electrified. If you touch anything with a hot-skin condition and an earthed object at the same time (even your bare feet on damp earth or concrete), you’ll be shocked and possibly killed. Find an electrician immediately and explain the situation to him. If he just plugs in a 3-light tester and tells you it's safe, make him watch my NoShockZone RPBG video. The entire electrical testing industry seems to be unaware or has forgotten this issue, so don't rely on old testing methods. 

So be safe. Test for RPBG conditions BEFORE you plug in your RV. And test your home outlets as well. You'll be surprised as to just how many RPBG outlets you'll find. Thanks Gary!


Click on Mike's name below for a brief bio!


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