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Switching the neutral #211003
09/01/13 02:22 AM
09/01/13 02:22 AM
Stu T  Offline OP
Joined: Mar 2001
Posts: 27
Stamford, CT
Can a standard 3 pole disconnect switch be used to switch 2 phase conductors and 1 neutral. My concern is the lack of accurate synchronization of the blades making to their respective contacts. If the neutral blade makes last it could cause over-voltage in the phase to neutral loads. Seems like the neutral blade would have to make 1st and break last. What about a 3 pole molded case circuit breaker ?
What do you think?
Thanks in advance.

Last edited by Stu T; 09/01/13 02:24 AM.
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Re: Switching the neutral [Re: Stu T] #211004
09/01/13 02:29 AM
09/01/13 02:29 AM
gfretwell  Offline

Joined: Jul 2004
Posts: 9,185
It is "legal" but certainly a design issue, for exactly the reason you brought up. Whether a millisecond or so of unbalanced load would hurt anything is really a question of what the load is.
It is also a situation where you fail very "hard" if the neutral fails to make totally.
I would avoid it if at all possible.

Greg Fretwell


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