Re: Does a GFCI need a ground?

On 25 Aug 2005 18:47:42 GMT, phil-news-(E-Mail Removed) wrote:

>On Wed, 24 Aug 2005 04:15:43 GMT Bruce W.1 <(E-Mail Removed)> wrote:
>
>| A ground fault circuit interupter senses the difference between hot and
>| neutral, and trips when they are not equal.
>|
>| Does it really need a ground contact?
>
>If you are hooking up a new circuit, put in the ground no matter what
>the GFCI needs. If you have an existing circuit without a ground, most
>(if not all) GFCI devices will function just fine.
>
>A GFCI serves to detect leakage current (an imbalance between the
>current carrying conductors, indicating that some other path is part of
>the circuit that should not be). The safety feature is to shut off the
>power when such leakage is detected, which may be going through people.
>The safety of having a ground is (among other things) a means to ensure
>metallic components of load equipment do not have any voltage potential
>from current carrying conductors, and provide a low impedance path to
>allow over current fault detection to activate properly if there is a
>short. Neither requires the other. Having both maximizes safety.
>
>--
>-----------------------------------------------------------------------------
>| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
>| (first name) at ipal.net | http://phil.ipal.org/ http://ka9wgn.ham.org/ |
>-----------------------------------------------------------------------------

Modern, up-to-date GFCI's on the North American Power Systems detect
(and will trip OFF) on two conditions.

1. Imbalance in HOT vs. NEUTRAL Current of 5 ma. or greater.

2. A short between NEUTRAL and GROUND (on the output side or
downstream from the GFCI).

As stated in previous postings, installation of new work requires the
3 prong outlet and a safety ground condutor. (In some cases, this can
be the conduit itself, if the other wires run in the conduit and the
conduit is grounded).

Old work (knob & tube and the ungrounded systems installed before the
late 1950's and early 60's) where the outlets just had a hot & and
neutral wire with NO ground wire.... These are the only places where
a GFCI is permitted to be installed with no ground. The GFCI outlet
should be marked "NO GROUND" to comply with the code requirements.

Beachcomber