Doug Miller wrote:
In article , "Twayne" wrote:

I don't think that makes sense so, assuming I'm right, how is it that an
overload on one isn't affected (delayed, held from tripping) by the force
the other needs to be opened?

It trips with ample force to bring the other one along with it, even if the
only connection is an external tie.

Move a breaker handle from the 'off' position to the 'on' position; notice how
much force you have to apply to it. Now nudge it from 'on' to 'tripped' -- see
how easy that was, and how forcefully it snaps over? More than enough to
trip a second handle tied to it.


Nice answers to some bizarre misinformation. I would disagree only that
if you have multiple breakers with a handle tie, one breaker tripping
will not necessarily trip the other breaker. The NEC requirement (if I
remember right) is for a common disconnect, not a common trip.

The common disconnect requirement was added in the 2008 NEC (or possibly
2005). Before that an edison circuit could have independent (and
separated) breakers. AFCI requirements do effectively limit edison
circuit usage.

Circuit breakers are "trip free". What you do with the handle )like
propping it with a 2x4) does not keep the breaker from tripping normally.


I thought maybe there was a different internal
structure somehow and they were electonically opened somehow, but I can't
find proof of that either. I did find one page (crecibility unknown) that
said both breakers operated simultaneously,

I guess that depends on what kind of time lag you would consider
"simultaneous". In the case of an internal common trip, they would in fact
trip simultaneously. With an external handle tie, there must be some tiny lag
due to mechanical play in the connection, but it's very small.


Multiple pole breakers (not just a handle tie) do have a common
*mechanical* trip and all poles will trip together.

--
bud--