"Charles Bishop" wrote in message
...
In article , "toller"
wrote:

It is called a multiwire circuit.
It saves a little wire and can be a bit more efficient on big loads. The
breakers are tied together because they share a neutral, and it is best
that
you turn both off it you turn either off. Also, tying them together
prevents you from putting both on the same leg; which is what someone did
to
one of mine. (Like 240v circuits, a multiwire uses opposite legs.)

Given that the house is wired with romex (12-2) is there a benefit to
doing it like this? I can see where there might be using 12-3, but if it's
just black/white/ground it seems like the same amount of wire needs to be
run. Maybe 12-3 comes into one of the j-boxes and they use 12-2 from
there?

Sorry, I "assumed" it was 12/3. The only reason to run two completely
separate circuits to a 240v breaker is that you have half of a outlet on
each circuit; then it is nice that they go off together.
But since you don't have that, I can only think the electrician was using
what he happened to have with him.