Caesar Romano wrote:
On Sun, 07 Sep 2008 22:05:03 -0400, wrote Re Code
question on generator grounding:
That breaker
has a mechanical interlock which prevents both it and the main
breaker being on at the same time. (It is impossible to turn on the
backfeed breaker on unless the main is off, and impossible to turn
the main breaker on unless the backfeed breaker is off.)
Where do you get such an interlock? Do you have a product name &
manufacturer? Even better, do you have a link?
They differ by panel model within manufacturer and are all hideously
expensive. Here's what I did on a Square D panel.
The connection to the generator goes to a double circuit breaker located in
the upper right column. For normal, non-emergency, operation, this breaker
is OFF.
It's possible to fashion a metal or plexiglass plate that nudges against
both the main circuit switch and this odd circuit breaker. This plate is
bolted to the panel cover via elongated holes in the plate that allow the
plate to slide, making contact with the two switch handles. The trick is to
match the sliding with the positions of the main switch and the odd breaker.
The breaker can't be turned ON unless the main switch is OFF. The main
switch can't be turned ON unless the breaker is OFF.
On a Square D, main switch ON is to the right and circuit breaker OFF is to
the right. If you have a block plate between the levers, it's obvious the
circuit breaker can't be moved to the left (ON) unless the main is first
moved to the left (OFF) and the blocking plate moved likewise. Similarily,
the main can't be moved right (ON) unless the circuit breaker is first moved
right (OFF) and the blocking plate scooted over with it.
Get the model and make of your panel and do a search on "{make} {model}
interlock" The results will give you an idea of how the manufacturer of your
panel wants the thing to work. You can then either find the best price on
the "approved" device or, as I did, fashion your own.