RE: GFIs and TCs

["Tesla list" <tesla-at-pupman-dot-com>]

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

Mathew,

I'm not stuck on a GFI at all; I just saw the thing in a water tight
box.  The plan all along has been to come off of the back side of the
200 Amp breaker supplying the house to another box/breaker right beside
it.  My house power just happens to be right where I do my coiling
(controlling).  I'm not up on the Code, but I figured I couldn't go
wrong if I used more than adequate wire size through conduit to another
UL approved box and breaker.  This way if everything on earth goes
wrong, I'll have no high current in the house at all.

Randy

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Wednesday, March 17, 2004 1:28 AM
To: tesla-at-pupman-dot-com
Subject: Re: GFIs and TCs

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


Randy wrote:
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.

Matthew replies:
You may want to put a normal breaker (not controlled by an RCD/GFI) on
your
main switchboard, running to a sub-board wherever you are doing your TC
work. You could then have a breaker (no RCD/GFI) for your pig, then RCD
controlled breakers for other stuff which should still have protection,
for
instance, power tools, anything that might get wet.

Ensure that the cable between the main and sub-boards is sized
adequately,
not forgetting to take into account:
a) the maximum current that your [hopefully ballasted] pig can draw
b) volt drop [I^2 . R]
c) ambient temperature (derating may be required)
d) proximity to flammable materials (eg: wood)
e) derating for enclosed/semi-enclosed

For circuits not protected by an RCD/GFI, make sure that you check
earth/ground continuity/resistance, Megger between phase and ground,
etc.  The local wiring code Is Your Friend; read it and understand it,
especially if you're planning to violate it ;-)

Building TCs is dangerous - modifying your house wiring no less so.

Cheers

M

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