multiwire branch circuits
- Thread starter jap2525
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- Massachusetts
Re: multiwire branch circuits
Handle ties are only a means to simultaneously disconnect all ungrounded conductors when someone manually opens the breaker. That is all the NEC requires for the range and dryer.
Again think of using a fused disconnect switch on any equipment. When a line to ground fault occurs only the affected phase opens, the other one or two phases stay hot.
However when you have to manually turn the item off one handle does it all.
[ October 15, 2004, 05:24 PM: Message edited by: iwire ]
A and B both will meet the NEC requirement.
Handle ties are only a means to simultaneously disconnect all ungrounded conductors when someone manually opens the breaker. That is all the NEC requires for the range and dryer.
Again think of using a fused disconnect switch on any equipment. When a line to ground fault occurs only the affected phase opens, the other one or two phases stay hot.
However when you have to manually turn the item off one handle does it all.
[ October 15, 2004, 05:24 PM: Message edited by: iwire ]
- Location
- Massachusetts
Re: multiwire branch circuits
We get back to how far should the NEC go to protect the unqualified from hurting themselves.
I would say this is just to protect the unqualified from flipping just one pole off and thinking all the power is off.
We get back to how far should the NEC go to protect the unqualified from hurting themselves.
izak
Senior Member
- Location
- Springfield, MO
Re: multiwire branch circuits
I think a 2 pole breaker feeding a split-wired receptacle is a Wonderful Idea
I think a 2 pole breaker feeding a split-wired receptacle is a Wonderful Idea
Re: multiwire branch circuits
jap2525, How would you know which neutral to disconnect? Probally by following the circuit conductor that you just turned off,and when you find it you will also find the other "hot" conductor of the multi-wire circuit in the same raceway,cable,etc.--On the other hand, if you removed a split yoke 2 circuit outlet and saw a black wire on half of it and a red on the other half you might think it is a half switched outlet. Even if you shut off the power and tested it {top or bottom only} you still have power,but with handle ties your "safe". That's my take on it.
jap2525, How would you know which neutral to disconnect? Probally by following the circuit conductor that you just turned off,and when you find it you will also find the other "hot" conductor of the multi-wire circuit in the same raceway,cable,etc.--On the other hand, if you removed a split yoke 2 circuit outlet and saw a black wire on half of it and a red on the other half you might think it is a half switched outlet. Even if you shut off the power and tested it {top or bottom only} you still have power,but with handle ties your "safe". That's my take on it.
izak
Senior Member
- Location
- Springfield, MO
Re: multiwire branch circuits
yes and whats to say that there would have to be a red and a black?
thats assuming that people wiring houses maintain a consistent wiring method thoughout the house, (which alot do not)
you might pull out a receptacle with two black wires (or two reds) on it and two whites and decide that this is a feed-thru or daisy chain
when you actually have two seperate circuits.
yes and whats to say that there would have to be a red and a black?
thats assuming that people wiring houses maintain a consistent wiring method thoughout the house, (which alot do not)
you might pull out a receptacle with two black wires (or two reds) on it and two whites and decide that this is a feed-thru or daisy chain
when you actually have two seperate circuits.
physis
Senior Member
Re: multiwire branch circuits
Bob, I've been under the impression that one of the reasons for handle ties is to interupt both poles of a 220 circuit in case of a fault. If I'm wrong about it being required I still think it should be done.
Be fair about it. My question was:
Edit: I meant B
[ October 16, 2004, 06:40 PM: Message edited by: physis ]
Bob, I've been under the impression that one of the reasons for handle ties is to interupt both poles of a 220 circuit in case of a fault. If I'm wrong about it being required I still think it should be done.
Be fair about it. My question was:
I personally would do B then C. But that's just me.
Edit: I meant B
[ October 16, 2004, 06:40 PM: Message edited by: physis ]
- Location
- Illinois
- Occupation
- retired electrician
Re: multiwire branch circuits
Sam,
Don
Sam,
The use of handle ties does not make a breaker into a common trip breaker. Common trip breakers have an internal trip that releases all poles of the breaker on a fault. Because breakers are required to be have "trip free" handles, it is unlikely that a handle tie will open the other poles when a single pole it tripped because of a fault. "Trip free" means that even where the external handle of a breaker is physically locked in the one position, that the breaker will still open under fault or overload conditions.
Don
Ed MacLaren
Senior Member
Re: multiwire branch circuits
When the home-owner (my girl-friends mother, who I was trying to impress ) turned the range element on, the kitchen light came on. This was my first experience with a back-feed situation.
Someone had installed two single-pole breakers with a handle-tie instead of a two-pole breaker, as the service disconnect, and only one side had tripped.
Ed
Very true. This fact resulted in one of my most embarrassing trouble-shooting sessions, and a lesson learned, many years ago.
When the home-owner (my girl-friends mother, who I was trying to impress
) turned the range element on, the kitchen light came on. This was my first experience with a back-feed situation. Someone had installed two single-pole breakers with a handle-tie instead of a two-pole breaker, as the service disconnect, and only one side had tripped.
Ed
pierre
Senior Member
- Location
- Westchester County, New York
Re: multiwire branch circuits
This thread has provided some very good insight into handle ties and common tripping breakers, but the reality of installing a 2 pole switch at a residential panel for the above mentioned type of circuit is almost unheard of, as a matter of fact, in my experience I have never seen this type of installation in a dwelling. Handle ties or a 2 pole breaker are the common methods.
Pierre
This thread has provided some very good insight into handle ties and common tripping breakers, but the reality of installing a 2 pole switch at a residential panel for the above mentioned type of circuit is almost unheard of, as a matter of fact, in my experience I have never seen this type of installation in a dwelling. Handle ties or a 2 pole breaker are the common methods.
Pierre
- Location
- Massachusetts
Re: multiwire branch circuits
When we are talking about handle ties we are talking about taking two or three single pole breakers placing them side by side in the panel and then installing a listed breaker handle.
I have never done this, we always buy internal common trip units.
It most likely is a common trip breaker, look on the side and check for the words "Internal Common Trip"
When we are talking about handle ties we are talking about taking two or three single pole breakers placing them side by side in the panel and then installing a listed breaker handle.
I have never done this, we always buy internal common trip units.
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