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RE: GFIs and TCs



Original poster: "Randy & Lori" <rburney6-at-comcast-dot-net> 



-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Tuesday, March 16, 2004 10:20 AM
To: tesla-at-pupman-dot-com
Subject: Re: GFIs and TCs

Original poster: Matthew Smith <matt-at-kbc-dot-net.au>

Tesla list wrote:
 >Original poster: "Randy & Lori" <rburney6-at-comcast-dot-net>
 >Does a GFI act as a circuit breaker in addition to just comparing
currents
 >on both lines? (Will it trip for excessive currents even if both lines
 >have matched currents?)
 >Also, do GFIs work well in TC applications? (would a rail strike trip
the
 >thing every time?)

Just to clarify, I believe that there may be two types of devices in
discussion here.

A GFI (ground fault interruptor?) sounds like what I'd call an ELCB
(earth
leakage circuit breaker).  As far as I am aware, this operates on
current
flowing through the earth conductor as opposed to an RCD (residual
current
device) or RCCB (residual current circuit breaker) which trips when
there
is a difference in current flowing through the phase/live/active/hot and

neutral conductors.  I seem to recall something from college about RCCBs

taking over from ELCBs.  Someone please correct me if I'm wrong.

An RCD will trip if you sneeze in the wrong direction or don't speak to
it
nicely - I have no personal experience of them supplying power to a TC
service but think that they would be Bad News(tm) as some of the "noise"

thrown back into the supply could cause them to trip.  Good filtering
and,
if available, a nice big isolation transformer could help here.

To answer the original question, our new consumer unit has a pair of 40A

RCDs, each protecting a number of circuits.  That's a 40A over-current
trip
plus a 30mA differential (RCD) trip in one switch.  Devices such as an
immersion heater and oven/hob do not pass through RCDs.  My thought
would
be to a) have a separate supply for your TC, not passing through an RCD,

provided that local wiring regulations permit it or b) if forbidden, ask

them to wire a point for your new electric oven in your shed/cellar/etc
;-)

Cheers

M

-- 
Matthew Smith
Kadina Business Consultancy
South Australia
http://www.kbc-dot-net.au

Thanks, I saw a 50A GFI on Ebay in a water tight box for Hot Tubs.
Since I want to tap the house wiring (My side of the meter), and keep
all of my Pig current from going through the house, I thought I would
ask.

Randy