According to TURTLE :

"Chris Lewis" wrote in message
...
According to TURTLE :

Hey you say it is legal but the fellow ask if the breaker set up in a set.
Will
one make the both of them trip properly as if they were seperated. Not being
smart at all but it even being legal will each breaker trip properly as one
side
getting over loaded and the other side not over loaded ?

tie-barred breakers (whether manufactured that way, or later add-on)
will both trip if either of the breakers overloads.

That's the whole point of tying the handles together.

I don't need a lesson in double breaker and them tied together at all and ask a
pin point question that you missed and did not answer.

That's actually the question I answered but without deeper detail. I'll give
the detail.

The question again here is : Useing one side off a 220 volt double breaker
circuit for 120 volt circuit. Will the one side heat up enough to trip both side
as if I had a single breaker on it ? Will the double breaker trip as fast as the
single breaker because of the other side may have a little little bit of a hold
to keep the double in gauged a split second longer ? I know this maybe a
judgement call for I have never seen any data as to it making any difference.

Most of this you already know, but in the interests of telling the full
story for others, and so you understand how it answers your question,
I'll include it all here.

The purpose of a breaker is to trip if the current thru the hot wire exceeds
specs (given time-delay/how much it overcurrents etc). It doesn't matter where
the current goes to (whether the other side of a dual in 240V applications
or thru the neutral in 120V applications (split or dual), or split between the
two in a multi-wire branch).

The current sense is done in a bimetallic strip (and/or magnetic depending
on OC levels) whose thermal response and resulting physical deflection is
not affected (significantly) by anything else is in the circuit.

Remember that the physical force required to throw the handle (and thereby
interrupt the current) is derived from the spring you tension when you
arm the breaker, and that the overcurrent "detector" (bimetallic strip etc)
merely trips a "catch" on that spring. The force required to move the
handle and interrupt the current is _not_ generated from the overcurrent
itself - it's from the spring. The force required to trip the catch
isn't dependent on what else is tiebarred to that handle.

In a tie'd breaker, then, the worst case is that only one breaker trips
the catch, and there's slightly more mass for the spring to move during
the initial part of the trip. But once the trip progresses "far enough",
it mechanically trips the other catch, and then you have _both_ springs
moving the tie'd handles.

So, if only one breaker OCs (which is likely even in a pure 240V
situation given variations in sensitivity anyway), the worst case is a
_slight_ delay in interruption due to Newton's "F=MA" equations ;-).

Now, consider this: these breakers are tested by the standards bodies to
conform within a certain OC-level/time-to-break curve. In _both_
"one breaker OC sense" and "two breaker OC sense" modes - because that's
what they see in the real world even on pure 240V circuits. Since they
passed certification, the time delay isn't significant in the certification
process.

Remember: breaker trip times are often quite long with mild overloads (often
10s of seconds). A few micro or milliseconds of additional delay trying
to get that other handle moving don't make no real difference.

There are probably some _extreme_ situations where it might make the difference
between a breaker self-destruct and a "normal" trip. But this
is already tested for up to the max fault current rating (like, 20KA or more),
and isn't an issue. With a direct lightning strike the thing might be
_slightly_ more likely to explode because it's a dual and not a single,
but at that level, you're going to have far worse damage than a fried breaker.

As a by the by, I should point out that some jurisdictions frown (or even
outlaw) add-on tiebars, perhaps depending on the equipment, and insist
upon "manufactured duals". The concern is that the tiebar may be so
loose that one side could trip but not the other. Or, that the tiebar
jams and one side (or even both sides) don't trip. Rather than spending
MUCH more time trying to cross-certify the breaker with every possible
"permissible" add-on tiebar making allowances for worst-case workmanship,
they just say "don't do that". Of course, in industrial/commercial systems
add-on tiebars are much more common, but that equipment is spec'd for it -
that's partly why it's more expensive.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.