Re: Power Applied?, and further wiring tricks..

To: tesla-at-pupman-dot-com
Subject: Re: Power Applied?, and further wiring tricks..
From: Tony Lekas <tony-at-lekas-dot-org> (by way of Terry Fritz <terryf-at-verinet-dot-com>)
Date: Wed, 07 Oct 1998 21:46:39 -0600
Approved: terryf-at-verinet-dot-com

You mentioned that you would run some smaller equipment from one leg of the
30A
240V circuit.  Your 30A breaker is actually two ganged 30A breakers.  If
either
leg draws too much power the breaker will trip and disconnect both.  If you
draw, say 5A, from one leg you limit the power available to the pig to 25A at
240V.  This is because one leg and breaker sees the pig current and the other
load.

Actually the breakers do not trip at exactly 30A.  It is a function of current
and time.  They will trip quickly at very high current, such as a short.  They
will stay on for a short time with a moderate overload.  They may eventually
trip if run near 30A for a long time.  You should not run the circuit at over
80% for a long period of time.

You should also provide a smaller breaker between the 30A circuit and the
smaller load.  The problem is that a short in your auxillary equipment will
need to draw more power to trip the breaker than the wire to it is probably
rated at.  The wire downstream of a protective device should never have a
lower
rating than the device.

        Tony