Opinions

As the Handyman see items be believes the public should know he will print them here.

• Changing a two prone outlet to a three prong outlet.

        NEC allows replacing a two prong outlet with a three prong as long as it follows a GFCI outlet. The Handyman has a problem with this. Why? Should the GFCI fail or should the neutral be lost after the GFCI, there is still power at the new three prone outlet. Let us say someone plugs a microwave into the new outlet and the neutral is lost. Next let us say for some reason the case of the microwave becomes energized. Assume someone is turning on the water and bumps into the microwave. Guess what is the shortest path to ground.

Note: In accordance with NEC Article 210-7(d), a GFCI receptacle may be used to replace an existing non-grounding 2-wire receptacle. In addition, existing non-grounding 2-wire receptacles may be replaced with grounding-type receptacles when they are supplied through a GFCI receptacle. (In this case, however, a grounding conductor should not be connected between the GFCI receptacle and those receptacles that it supplies).

If someone can explain to the Handyman that this could not happen, please let him know. This post will remain and the explanation will follow.

Peter:

I sent them this explanation-

The GFCI operates by detecting any difference [as low as 6 mA] between the current going out the hot terminal and returning on the neutral. In the scenario, the neutral is broken between the GFCI and the new outlet. For one thing, the microwave would not work. But in this state, the GFCI would not trip because there is 0 volts going out compared to 0 volts returning. Then the scenario continues with the hot wire touching the frame of the microwave and someone touching the frame and also ground. Then power would flow thru the hot, the MW, the person and the ground – but none would return thru the neutral. These would be read as an imbalance by the GFCI and it would trip.

Hope this answers your question

Handyman:

I forgot about that. That being said, I have seen GFCI’s not trip. Also, does the GFCI neutral reference have to be at the GFCI. I am waiting for a response from Leviton.

The reason I pose the question here is I find that there are a lot of us non-engineers that see things differently.

After I am convinced I understand, I will still leave the post on my site so that others will not replace 2 prone with 3 prone without using a GFCI.

Thanx A good explanation.

Handyman

As far as the GFCI not tripping, either the unit is defective (testing with an external tester would reveal this) or it’s miss-wired (for example, the down line receptacle connected to the source side of the GFCI instead of the output side).  Note that I prefer using an external tester for a definitive check to eliminate the possibility of a defect in the test circuit of the GFCI.

As to the “neutral reference”, the key is the current flow.  As long as the down line device is connected to the output or load side of the GFCI, it will have the same protection as the sockets on the GFCI itself.  Both the hot and the neutral have to be connected to the GFCI load side.  That way the comparator circuit is able to detect whether all the current is “coming back” through the neutral and not leaking to ground via some other path (such as a hapless user).  The beauty of this is that the protection is only concerned with the hot and neutral and doesn’t care what the alternate path is, only that it exists.  It only takes a few micro amps (not even enough to feel) for the GFCI to detect a fault and trip out.

I apologize for the length of the explanation, but I hope it helps to put your mind at ease.

Ray.

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