2-Wire and GFCI

[Francis Vineyard]

Thought I pass along this information for those of us still dealing with knob & tube, and 2-wire romex. I prefer to use my personal fluke tester to test GFI outlets; occassionaly it reveals wiring problems that otherwise go undetected with the receptacle test button.

“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”

http://www.rvdoctor.com/2001/07/friends-of-gary-mike.html

Francis

 

[BSSTG]

Greetings,

Bear in mind also that it is perfectly fine and allowed to install a 3 wire gfci on a 2 wire circuit. It will work fine in reality but will not test propertly with a 3 wire tester. That's why the code requires any outlet that is wired with 2 wires, and protected by a gfci to be marked, "no equipment ground". Additionally, any 3 wire outlet outlet fed by 2 wires and protected with a gfci to be marked,"no equiment ground" and "gfci protected". Otherwise, replacement outlets on a 2 wire standard circuit must be replaced with 2 wire outlets. Bottom line is that your standard 3 wire gfci tester will not trip the gfci's on a 2 wire circuit when testing. I have found that there are quite a few inspectors that have not known that over the years.

The above mentioned scenario should still be safe as long as the gfci is working properly. Even if polarity is reversed, and there is a ground fault, the gfci will ordinarily trip.

BS

 

[Francis Vineyard]

Be it known we are certainly not condoning that the polarity allowed to be reversed.

The situation has occurred where an appliance housing was (hot ground) "energized" not creating a shock until wet mopping and contact between it and a nearby appliance in a different outlet.

Francis

 

[BSSTG]

Be it known we are certainly not condoning that the polarity allowed to be reversed. The situation has occurred where an appliance housing was (hot ground) "energized" not creating a shock until wet mopping and contact between it and a nearby appliance in a different outlet.

Francis

Greetings,

Yea it's not a perfect world! I look at a lot of old houses here and I run into some stuff that makes me wonder how there are not more house fires and electrocutions than there are. Thank the Lord those happenings are uncommon.

BS

 

[Builder Bob]

Besides, any old electrician will tell you - to run a pigtail or a jumper from the neutral to the equipment ground...... that is why the plate cover needs to be off at final..... IMHO.