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Old 10-26-2011, 12:28 PM   #16
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Just curious


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Originally Posted by Billy_Bob View Post
P.S. The difference is that a MWBC in a home is not using 240 volts whereas the 240 volt circuit is.

And I am not a circuit breaker guru, but it is my understanding that a 240 volt breaker is internally connected, so if one trips, the other trips as well????

Whereas for MWBC, it would be two separate 120 volt breakers which have a tie-bar added????

I tried searching for this info several years ago, but couldn't find anything. Anyone know? Does not matter? Does matter?
A 2 pole breaker has an internal common trip, yet there is no requirement to use one for a dryer or a range. 2 single poles and a handle tie is legal.

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Old 10-26-2011, 12:47 PM   #17
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Thanks!

That did it! The word "common".

I googled common trip breaker and found all sorts of stuff on this.

(Took me a few years, but better late than never. I was searching for internal trip...)

Anyway I found there is a difference between a double pole breaker with an internal or external "common trip", and two single pole breakers connected with an add-on tie-bar.

With the common trip, if one breaker trips, the other trips as well.
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Old 10-26-2011, 12:52 PM   #18
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Originally Posted by Billy_Bob View Post
Thanks!

That did it! The word "common".

I googled common trip breaker and found all sorts of stuff on this.

(Took me a few years, but better late than never. I was searching for internal trip...)

Anyway I found there is a difference between a double pole breaker with an internal or external "common trip", and two single pole breakers connected with an add-on tie-bar.

With the common trip, if one breaker trips, the other trips as well.
Correct.
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Old 10-26-2011, 01:00 PM   #19
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Originally Posted by Code05 View Post
A 2 pole breaker has an internal common trip, yet there is no requirement to use one for a dryer or a range. 2 single poles and a handle tie is legal.
I'm not sure that's true. Do you have a code reference? 210.4C Ex. 2 seems to disagree.
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Old 10-26-2011, 01:16 PM   #20
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Originally Posted by mpoulton View Post
I'm not sure that's true. Do you have a code reference? 210.4C Ex. 2 seems to disagree.
Exception No. 1: A multiwire branch circuit that supplies
only one utilization equipment.

Quote:
Exception 1: A multiwire branch circuit can supply line-to-line utilization equipment, such as a range or dryer.
From here:http://ecmweb.com/nec/code-basics/el...circuits_part/

Last edited by Code05; 10-26-2011 at 01:27 PM.
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Old 10-26-2011, 08:38 PM   #21
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A 120/240 volt "multiwire branch circuit" is electrically the same as and constructed in the same way as a "240 volt circuit with neutral" to serve an appliance such as a clothes dryer with both 240 volt and 120 volt components.

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Last edited by AllanJ; 10-26-2011 at 08:44 PM.
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