Re: GFIs and TCs

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

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