Can a GFCI work without a ground???

Being an electrician myself, I run across all sorts of myths about electricity.  Things like "the white wire is never a hot wire", "wirenuts must be taped", and "GFCI's will trip if overloaded", are just a few.  Unfortunately, I've ran into several customers who knew just enough about electricity to be dangerous.  And many of their costs would have been considerably less if they'd just called me before they ever done anything to begin with.  It's much easier for an electrician to start from nothing than it is for him/her to trace someone else's work.

 Now that you know that many of the things you "know" about electricity my be false, don't lose your respect for it.  In fact, you may want to gain some.  Electricity is a very dangerous thing, indeed, and the fact that many people get killed from it is NOT a myth.

First we need to understand how a ground fault circuit interruptor (GFCI) works.  It is not like your breaker in your service panel.  A breaker will sense the amps flowing through it and will trip if the amperage flow is greater than what the breaker is designed for (providing that it is working properly!!!) 

A GFCI does not care how many amps are flowing through it, and therefore it is feasible to overload the thing.  To keep it simple, put a 15-amp GFCI on a 15-amp circuit and put a 20-amp GFCI on a 20-amp circuit.  How do you know which one you have?  My photo above is a 20-amp device.  The easiest way to tell by looking at it is that the 20-amp has a tee on the neutral side (the wider opening).  A 15-amp device will not have this tee on the neutral side, but simply a single slot.

The GFCI is able to sense the electricity flowing in the hot side as well as what is flowing out the neutral side.  If there is a difference in amperage there (most GFCI's can measure to a degree of 0.005 amp differential), then there is a power loss.... In other words, someone or something is getting shocked.  Then the GFCI will trip.  It doesn't care whether it is overloaded or not, so make sure you have the correct size breaker on it, and it doesn't care whether you are getting shocked or a piece of dirt wedged in there somewhere.  It will still trip. 

So what about the ground???

 The fact about the ground is that it is there to catch any loss of electricity so that we don't take it in (get shocked).  But if there is a loss of electricity through GFCI, then the unit will trip anyhow.  A GFCI uses the Hot and Neutral conductivity and does not need a ground to work properly.  This does NOT mean that you can simply cut the ground wire from it.  The casing still needs to be grounded.  Note that I said that the unit will trip if the electricity is lost THROUGH the device.  The casing has nothing to do with the conductivity through the GFCI and still must be grounded.  I'm simply showing you that the GFCI does not use a ground to keep you from getting shocked.

Please remember, don't be "that guy/gal" when tackling even small jobs with electricity.  If you know enough to be dangerous, then you are certainly smart enough to call a professional for help.

Thank you.....