Re: Potentially stupid question about AC

[supertimer@aol.com (Supertimer)]

david@uow.edu.au (David Wilson) wrote:

>Many houses now have ELCB (Earth Leakage Circuit Breakers) which trip if the
>current in the active line is not equal and opposite to that in the neutral
>line. This indicates that power is getting to ground either via the ground
wire
>or through something or someone else.

I think this device is called a GFCI (ground fault circuit interupter)
in North America.  All hair dryers are required to have one and
they are also typically installed in sockets near water.

>Double insulated gear omits the ground wire and replaces the metal case
>with two independent insulating layers.
>
>Our plugs are Crowfoot so polarisation should always be maintained.
>
>active	/	\  neutral
>
>
>	    |  earth

North American plugs have parallel prongs, but one is bigger than
the other.  Except in older homes where both prongs are the
same size.

Actually, I've seen an old house that lacked both polarized
plugs AND the third ground line at the outlets.  That's pretty bad,
isn't it?

>>And why is it dangerous to defeat a polarized plug?
>
>The device may only have a single pole power switch which breaks the active
>line. The fuse should also be in the active lead.