| [GMCnet] Power distribution using circuit breakers [message #97285] |
Thu, 26 August 2010 10:16 |
tmaki
Messages: 200
Registered: September 2005
Karma:
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Senior Member |
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> Power distribution using circuit breakers
>
> Many of us have been using circuit breakers rather than hidden fuses for
> power distribution in the GMC.
>
> There are many advantages to this application and these slides describe some
> of these features:
Yes, Gene. An excellent solution to the "fuses hanging off
unidentified wires" situation. I use many of them myself.
One caution, however, for those not familiar with these
circuit breakers. I did a service bulletin for Brand F back
in about 1982 that addressed the installation of these. I
had noticed on the schematic and production prints from the
PD group that they indicated installing them so the load
side broke, rather than the source side. Internally, these
breakers - unless they have been re-designed since then -
break in such a way that the thermal strip can - and will -
contact the metal case. Since the case can and often is
attached to a grounded object like a frame member or a
ground buss bar, if the source side is connected to the
wrong terminal, when the circuit breaks, full source current
is shorted directly to ground. After explaining it to the PD
manager, they had to change the production prints.
Fortunately, I don't think any units were built incorrectly.
These breakers can have values that will carry 20, 30, 40,
50 amps or more. A direct short to ground of that kind of
current can be quite entertaining for anyone standing around
watching. And quite destructive to one's ego or vehicle.
Caution: Be sure you know which terminal is source and which
terminal is load. Not all of them are color-coded -
particularly many from our favorite off-shore suppliers.
Most have different length terminals, but verify which
terminal is which. If you buy a batch of them that are not
marked in some way, they are cheap enough to disassemble one
and make sure.
Toby Maki
'73 Glacier 230
Riverside, CA
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