Wired permanent bathroom light this weekend...had been using a pigtail for temporary construction lighting. This light is switched conventionally (no switch loop) and gets power though the load side of a GFCI outlet, and shares the triple box with outlet and fan switch.

Didn't bother to switch the circuit breaker off, since the wires to the new light were definately switched OFF. During the wiring of the light, I naturally held the stripped ends of both black and white wires, and the EGC wire while straightening them...and the GFCI breaker popped, but I did not get shocked.

So the GFCI must sense un-natural grounding even if there is no power to the protected appliance.

Also wired the OTHER bathroom light, which gets power from ANOTHER GFCI protected circuit via an oulet in the garage, and is also conventionally switched. Same thing, go to put in the bulb...no light. GFCI breaker had popped!

This , BTW, was all inspected at rough-in and passed.

 

If the neutral goes to ground downstream of the GFCI , It will trip.That is what it is supposed to do!

 

That's what I thought. (at least 99% sure) I just think it's an interesting way to explain what is actually going on in the breaker and to test the functionality.

 

Yet another reason why you should always shut off the breaker and not just the wall switch (even when no switch loop is involved). When the neutral and ground connect to each other at the dead light, the ground becomes a return path for anything else on the circuit. The switch only disconnects the hot wire. You can get killed by a neutral wire too.

 

"the ground becomes a return path for anything else on the circuit."

But under normal operation, (ie. nothing faulty on the rest of the circuit) the ground or neutral will not carry any current, will it?

Not trying to justify shortcuts, just trying to understand.

Thanks.

 

The neutral will be carrying current, unless it is on a 100% balanced multiwire branch circuit.

You will find alot of info. here..........http://www.ibiblio.org/obp/electricCircuits/

 

In most circuits, the neutral carries exactly the same amount of current as the hot.

 

Are you saying that if something else on the circuit had been running, motors, lights, etc, I would have gotten a shock when I touched the bare neutral wire and the EGC at the same time?

But would NOT get a shock with the hot switched off and no other loads on the circuit?

 

If there were no faults in the system (i.e., the neutral was well-connected everywhere), the most that would be on the neutral line would be a couple of volts. Probably not even enough to notice.

If the neutral had a poorly-made (i.e., high resistance) connection somewhere, and other loads were running, there could be enough voltage on the neutral to shock you.

If the neutral had an open-circuit somewhere, and other loads were switched on (but of course not actually running), there could be a full 120 volts on the neutral, enough to kill you in the right circumstances.

And of course if the light is wired with a switch loop (which is not your case), then turning off the switch provides very little safety as there is still a full 120 volts in the box even with the switch off, no other loads, and no faults at all.

Bottom line: shut off the breaker.

 

Crystal clear.

Thanks.