Fernando Gonzalez Gentile wrote:
> on 7/05/2006 12:18, Joe Gwinn at joegwinn@xxxxxxxxxxx, wrote:
>
>
>> Bypass the circuit breaker? Not a good idea - it's a good way to
>> burn the house down.
>>
> Joe, I have six circuit breakers at home. Two of them at the main electrical
> input, in a parallel setup. One of these shuts when wiring temperature
> rises, and the other shuts when anything that might be wrong happens.
First, a terminology clarification about circuit breakers, switches,
etc. In common electrical usage in English, closed means the circuit
through the breaker is complete and power is available on the protected
circuit. Open means there is no continuity across the breaker and power
is off to the circuit. This is apparently the reverse of your
terminology. A circuit with a broken wire is an open circuit. Just to
guard a bit against misunderstanding.
This can't be correct. If wired in parallel, the operation of either one
would have no effect on current flow, it would simply go through the
other. They would only each be able individually to break the circuit if
wired in series. I have no idea how power distribution works there. For
domestic power in the US, there are generally two breakers at the main
input, one for each 120v side of a 120/240 volt, center neutral, three
wire system.
> Only the latter is bypassed so as to make a single dedicated power supply line
> for my audio equipment. This Merlin-Gerin breaker waits until I go out on
> vacations to shut, when all other breakers are shut before leaving and only
> the fridge and the alarm system remain On.
>
This is pure, semi-deductive guesswork, to be taken as worth what it
costs. Assuming the second breaker, which opens when something other
than simple excessive current is wrong with the circuit, does something
like the GFI breakers we use here, it will be measuring differences
between the current going out through the hot lead and that returning
through the neutral and possibly measuring current through the ground
lead. As you explain the problem, it gives no trouble when you are home,
all breakers are closed, i.e. all circuits powered up, and only fails
when almost all circuits that it feeds are open. It fails when there are
periods when only extremely small currents flow through it, as when the
fridge is not operating its compressor and only a trickle of current
goes to the alarm.
The obvious logical conclusion is that this breaker only fails when it
is not connected to circuits that provide use some minimum amount of
current. It may be that under those circumstances, ground loops, a
limitation in the breaker itself, or a fault in the breaker cause false
readings of leakage between the circuit and ground or differences
between out and incoming currents and the breaker opens.
The first simple test I would try is to leave a secondary breaker
operating and leave a lamp (Or two, so a blown bulb doesn't ruin the
experiment.) on next time I'm going away for a while. If that cures the
problem, you would know that it is either a design limitation in the
breaker or a faulty breaker.
Moose
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