Re: GFCI
| Subject: | Re: GFCI |
| From: | Brandon Jones |
| Date: | Fri Apr 26 01:00:00 1996 |
> >(which means that the mA is sneaking off somewhere where it shouldnt).
> >If thats true, why would the "GFCI have to be grounded to earth?". I
> >kinda thought the ground wire was just there to provide a connection to
> >the third prong of the outlet, not really part of the GFCI circuit.
> >Jim Burrows
> Hmmmm....... after I thought about it a bit, I think you may be right. I
> have never actually looked at the design of a GFCI, so I am not sure, but I
> guess it really is a current comparator, looking at the two sides of the AC
> line. That function would not have to be ground referenced.
>
> Paul
You are both essentially correct.They measure the line and neutral
currents and if there is a difference by greater than the regulation
current the device trips out.The earth pin is used to comply partly
with regulations on the basis that the devices give a warning
of a dis-connected earth connection.This is usually done by a
simple neon lamp indicator that lights up when the earth is not
connected.The other reason is that the device has to have a test
circuit.This is a resistor to earth via a pushbutton.The earth pin
has to be there to make this work.
Brandon S.Jones
