Find which circuits they're on. If they are on the same side of the
breaker box and there is an odd number of breakers between them (not
the numbers, but the spaces) they will likely be on the same leg. If
they're on the opposite side, count evens. This isn't 100% assured,
but it should work. A peek inside will tell you for sure.
Find out what breaker the receptacles are on and then look at where
those are plugged in. They're interleaved with every other breaker down
the row being on the same bus. If they're on opposite sides you can
usually swap two side by side breakers to get the one you're interested
in on the side you want it.
Like the original poster, I was talking about 120 volt circuits and then
expanded upon your answer to clarify when a 3-wire is is used as the homerun
to the panel. A 240 volt load has nothing to do with it. With a 3-wire
homerun, the black and red have to be on opposite phases in order to have
the neutral carry the unbalanced load. If the breakers for the black and red
were on the same phase, then the neutral could end up carrying the full load
of both circuits and burn up. So because of potential 3-wire homeruns, one
cannot simply swap breakers that are next to each other without knowing if
it can be safely done.
We were talking about outlet circuits, and as you can see above I wrote,
"Not if the breakers go to a 3-wire". I specified breakerS and 3-wire. What
other conclusion would or could anyone draw from that?
An air conditioner, dryer or range with a combination of 120 & 240
volt loads. I can't remember exactly the last time I saw what you are
talking about. Probably sometime in the '60s.
Like I said, be specific. This is a world wide group with people
using different electrical systems and having different levels of
An A/C, dryer, or any other 240 volt device/appliance would use a single
2-pole breaker, it would not use breakerS. For Christ's sake be man enough
to say you mis-read what was written, or your brain wasn't operating at 100%
that day, and knock of this trying to justify what you wrote crap. For the
record, 3-wire homeruns to a panel to feed two circuits are very much used
still today and are not indicative of 1960s wiring.
So, you've never seen were some scab used a pair of breakers for a
repair to keep up the number of jobs per day, or when 'Mr. Fixit' didn't
want to buy a two pole breaker when he already had a spare single pole?
Both knew that there would be no inspection of their crappy work, and
things would work long enough to get paid, or flip a crappy rehab.
What a sheltered life you must lead. Some of the things I find would
cause you to blow out your brains. I was called in to help troubleshoot
a home with multiple intermittents a few weeks ago. It had multiple
intermittent neutrals, and a piece of 12-2 W/G used to tie the old
wiring into the newer part. They ran two 120 V 20A circuits and used the
16 gauge ground wire for neutral, and both supply lines were on the same
phase. It was no wonder that 16 gauge wire was burnt. BTW, the two
circuits were on separate breakers, and the white wire had no phase
As far as " For the record, 3-wire homeruns to a panel to feed two
circuits are very much used still today and are not indicative of 1960s
wiring.", I never liked that method and don't remember ever using it.
It was considered a cheap trick used by 'fly by night' companies.
I like them and they certainly have been common in the past. For example
I can think of a hospital where substantially all the 120V circuits to
patient rooms started as 4-wire 3-phase multiwire branch circuits. Other
circuits were also mostly multiwire. But the 2008 NEC requires a
"simultaneously disconnect" for multiwire branch circuits. That does not
have to be a multipole breaker - it can be single breakers with a
(listed) handle tie. It would make multiwires in the hospital impractical.
AFCIs have probably eliminated most multiwire branch circuits in houses
since you can't have a common neutral unless the AFCI is 2-pole. You may
be able to get a 2-pole AFCI, but they probably cost far more.
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