Pay careful attention to these breakers

Originally Posted By: jpeck
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Joe M.,


Those are NOT "multi-wire circuits". Those are 240 volt circuits, and those breakers are still made, in fact *preferred* for 240 volt circuits.

I also prefer them for multi-wire circuits, however, for multi-wire circuits, the two do NOT have to be tied together, unless they are on the same strap. In my opinion, they SHOULD be tied together.


--
Jerry Peck
South Florida

Originally Posted By: jpeck
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jtedesco wrote:
get it yet?


Nope, I must be totally glazed over, because I have no idea what you are referring to (with your reference to multi-wire circuits) and not referring to the use of the half-size breakers on the same bus bars (as in my other post).


--
Jerry Peck
South Florida

Originally Posted By: jtedesco
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If the red and black wires in a cable that has a white wire and bare equipment grounding conductor is considered then it will be easy to understand.


If the black and red wire are connected to the terminals of the twin breaker, that is on the same phase, the white wire will carry both loads. Assume a 15 amp load on each -- the white wire will carry 30 amps and will be subject to burning up.

A multiwire branch circuit includes a grounded conductor (neutral) and two or more ungrounded conductors "hot legs"

210.4


Courtesy: www.iaei.org "One and Two Family Dwellings"


--
Joe Tedesco, NEC Consultant

www.nachi.org/tedescobook.htm

Originally Posted By: roconnor
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Great explanation with the diagram Joe … eusa_clap.gif


Also consider that if you see a lot of twin breakers, it's a mind flag that maybe that panel just might be overloading the service ...


--
Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee

I am absolutely amazed sometimes by how much thought goes into doing things wrong

Originally Posted By: jpeck
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Joe T.,


That what I said, at least I think it was.

Quote:
This is because, in Joe T.s reference to multi-wire circuits, multi-wire circuits may only be used off full size breakers, so one breaker is on one bus bar and the other breaker is on the other bus bar, making 240 volts between the breakers, thus making the shared grounded conductor a true "neutral".

If these (half size breakers) are used for multi-wire circuits, then there is -0- volts between the multi-wire circuit conductors, meaning the shared grounded conductor is not a "neutral", but a twice loaded grounded conductor (carries the full current of each circuit, thus could easily overload the grounded conductor for its size).


Of course, your drawing is much better at showing it.

And, yes, I did refer to "half size" breakers, because they are the ones most often misused for multi-wire circuits, but full size breakers can also be misused that way, as shown in your drawing.


--
Jerry Peck
South Florida