On Sat, 04 Jun 2005 14:37:24 GMT, "Jerry Foster"
wrote:
"xray" wrote in message
.. .
Usually I can figure this stuff out myself, but I don't see the answer
here and never had occasion to do it before.
In the electric box that feeds my house, I want to replace one circuit
breaker. What holds them in?
I think my box is pretty standard. There are busses for the two legs of
220 down the middle and some kind of clamp strips down the outsides that
holds the CBs.
Hope that is enough info for an answer.
Tell us the brand of the panel and the models of the breakers, and
we can easily answer the question. Or stick a picture up somewhere.
Most modern breakers plug straight onto the two rows of buss stabs
in the middle of the panel, and they have hooks on the outboard side
to keep them in the panel. Cutler Hammer CH and "Challenger" or
"Bryant" BR, Crouse Hinds/ Murray/ Siemens MP QP, GE THQP THQL,
SquareD Homeline, etc.
The hooks are 'coded' in some panels, and the buss stabs notched to
reject double breakers in a large 42-breaker panel. And some brands
have other odd rejection methods, like the pins in the back of some
FPE panels that fit in holes in the back of the right breakers, and
all their odd buss stab plug patterns.
Square D "QO" has two spring clips, one for the hot buss, one for
the locating rail. Except for some of the old QOT tandem breakers
that use a metal hook for the locating rail, restricting them from
being used in certain Non-CTL panels. (Keeps you from going over 42
poles in a panel.)
Same two-clip design with the antique SquareD and Cutler-Hammer XO
design breakers - if you have an XO panel, plan to change it. You are
NOT going to find replacement breakers for anything approaching a
reasonable price, and they're going to be used take-outs.
SOME boxes in older homes use "Pushmatic" breakers. These are held in with
a screw. And the screw is, as I recall, hot. So, regardless of the type of
breaker, turn off the main before you try removing it.
True, though bolt-on breakers other than ITE Pushmatic are usually
found in industrial panels. It's legal if they have 'walked home from
the plant' and been installed in houses, but finding replacement
breakers is a supply-house-only pain in the ass. You usually find a B
in the part number as a good clue.
If you have nerves of steel you can change bolt-on breakers with the
panel hot - though you need to take proper precautions like using
insulated tools, cardboard or plastic to isolate open hot stuff that
can be blocked off, and a screw-grabber screwdriver to avoid dropping
the screw into hot areas - they're JUST long enough to cause shorts if
they land in the wrong place.
And you can /not/ trust any screw retaining washers or devices used
on bolt-on breaker line tabs 100%, they sometimes don't retain the
screw when called on, with potentially disastrous results. You
usually see the thin retainer tab under the screw on original
Pushmatics.
In other words, if you don't do this stuff every day, take the safe
route and turn power off to the panel before poking around inside -
and get a Wiggy so you can be assured it's really dead.
I even turn stuff off if I think something is seriously wrong inside
- like the supports are broken or burned, and hot parts might spring
together and short out when I take the breaker out.
Discretion in electrical work is the better part of being able to
count to 10 without taking off a shoe. (Or counting stumps.)
-- Bruce --
--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545
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