| Because Until ABSOUTLY every appliance that is ever likely to be pluged | into an outlet has only a 2 pin plug, then every outlet must provide the | ground, that is pass it thru from the outlet to anyting plugged into the | GFCI.
Won't happen. Some things absolutely need the grounding wire.
The internal test button on all GFCI's will work just fine without a ground. It only uses the grounded and ungrounded conductors, and does not rely on the grounding conductor at all. You can not use an external tester, however, since it rtequires the ground circuit to bypass the sensing coil.
Ben Miller
Take a toaster into the bathtub?
;-)
Before or after you stick your toe in the water to make sure it is the right temp? :D
You don't need a ground to simulate a "ground fault." The "fault simulator" would, say, go from HOT on the load side to NEUTRAL on the line side. That would trip it. With most GFCI, you can just connect the test resistor between the line and load neutrals and it will trip.
Yes.
Not nearly as precise. You are providing a leakage path across the sense CT drop which isn't precise and varies with load.
Not very precise either. But the failure annunciation is pretty clear.
8-O
Connecting a GFCI with a ground is always preferred should one be available.
However, the NEC allows a specific exception for the old 2 wire ungrounded circuits the are still prevalent in some older buildings. The code allows placement of a GFCI and it will still trip if there is
put a little sticker on the outlet to inform the users that the 3rd prong ground hole is not really connected to the ground.
Beachcomber
Right. The ground on a GFCI isn't there for proper GFCI operation. Its to allow an alternate fault current path in the event an appliance suffers an internal short to its chassis and is equipped with a ground conductor (3rd prong). Without the ground, the chassis will just become energized and sit there until someone closes the circuit by touching it. Although the GFCI will limit the duration of current through the individual, it does not limit the current magnitude. If the curcuit resistance is such that 50 or 100 mA will run through someone, it will do so, GFCI or not. We only hope that the GFCI will cut the circuit before too much damage is done.
The ground provides a return path to trip protection at the time the fault occurs, not later on, when someone grabs the appliance.
Perhaps some further elaboration is necessary... GFCI's work on sensing the differential between the hot and neutral wires. It is true that if an individual diverts some of the hot wire current (through a fault) and if all of it is returned through the neutral, the device will not trip. Grabbing the two prongs of an outlet while pulling it out of the wall would be an example.
This is not typically the case however. A grounded surface can be found in a water pipe or a wet or damp basement floor. If this becomes the return path (instead of the neutral) , and the current exceeds 5 ma., the device will trip. This is the whole reason for installing GFCI protection on a two-wire ungrounded circuit in the first place. As I said earlier, a separate, electrician-provided ground is better, safer... but if the ground is not there, a GFCI installed on the circuit will provided a limited degree of safety vs. not having one installed.
Beachcomber
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