Recently, I was changing a light fixture on my back porch and
discovered that I had to shut off two breakers to cut the power to the
circuit. I take that to indicate that somewhere, somehow the two
circuits have effectively been crossed together such that the circuit
can draw power from either breaker.
I'd like to fix this... is there a simple way of determining where the
two circuits are conjoined?
It is not that uncommon to have to turn 2 or more breakers off in order
to completely shut off the power inside a single switch box. This is
especially true of 2 or 3+ gang switch boxes that say lead to the garage
from the kitchen etc.
If you are saying that it takes 2 breakers to shut off a single light
then that is a crossover. The first place to look is in the switch box.
If not that then I would map out your entire system by systematically
turning the 2 breaker on and off. Then find all the outlets or lights or
appliances that come on with both beakers. Then open each box one by one
until you find the problem.
There are other possible situations that could cause this kind of
behavior such as an open neutral. But you would notice other problems
like brighter and/or dimmer than normal lights elsewhere.
Sometimes neutrals from 2 different circuits are connected together
somewhere and when you go to disconnect things you get an arc/shock as
you are disconnecting the neutrals at the fixture box even though the
power is off on the circuit you are working on BTDT. In this case the
circuits are not really joined but you should go and try to separate the
neutrals if you can. Most likely this was done in a 2+ gang switch box
fed by 2+ circuits.
An Edison type (shared neutral) circuit where a duplex outlet is fed by
2 circuits someone replaced an outlet and forgot to break the joining
tabs between the upper and lower outlet. If this were the case however
the circuit would have a second problem where the 2 circuits were
improperly put on the same 'leg' in the panel.
This could also be two circuits that use a common neutral. That would
happen if you ran 12/3 like in a kitchen where the top receptacle is
on one circuit and the bottom on the other, but they both share the
neutral. Code requires that the breakers be tied together so both must
be shut down to avoid killing somebody who thinks they're working on a
After a bit of thought, I realized that there was a single switch box
in the kitchen that contained lights from both circuits...
one switch (a 3-way) controls the light in the foyer and the rest
control kitchen lights. That seemed like a likely spot
to start looking so I pulled it open. I discovered that all of the
neutrals in the box were tied together, crossing the two
circuits together. I pulled the incoming and outgoing neutrals for
the foyer light out and tied them together separately
and the problem is fixed.
Thanks to all for the advice.
On Oct 28, 9:24 am, email@example.com wrote:
What fire hazzard, here it was to code. I have the same thing to the
garage and its not going to be fixed until underground wires to the
garage fail because I would have to trench up a yard and sprinkler
system. I was told its called a California Loop, what ever that is, it
was common years ago here to a garage that needed more than 15a, just
learn to lable breakers and live with it if its a similar 3 way set
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