Sharing the neutral?

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Smart $

Esteemed Member
Location
Ohio
Hey guys! Where is it in code (2011) that you can't share a neutral on three phase circuits any longer?
If by 3? circuit you mean MWBC, 2011 doesn't prohibit such, but either have to use a 3-pole breaker or install a handle-tie on 1-pole breakers.
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
Installing a common tie handle is cheaper than the wire. I am not sure if manufacturers have seen an increase in sales???

Most customers do not want it that way, engineers especially, in order to turn off one circuit, all three have to be turned off, so instead of a small outage, a big one happens.
 

haskindm

Senior Member
Location
Maryland
Most customers do not want it that way, engineers especially, in order to turn off one circuit, all three have to be turned off, so instead of a small outage, a big one happens.

So what? The code is about safety, not convenience or power reliability. MWBC on single pole breakers without handle ties are bad news. Too easy to de-energize one leg and think the entire circuit is de-energized or break the neutral when two legs are still energized. I know an "electrician" should know better, but this is not the first instance where the code has been "dumbed-down" to try to protect the untrained....
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
So what? The code is about safety, not convenience or power reliability. MWBC on single pole breakers without handle ties are bad news. Too easy to de-energize one leg and think the entire circuit is de-energized or break the neutral when two legs are still energized. I know an "electrician" should know better, but this is not the first instance where the code has been "dumbed-down" to try to protect the untrained....

The thing is, even if your mwbc only goes to the first j box, then splits out from there, if you want to add some thing on one of the branches, and not breaking the neutral at that point, you are still required to have the handle ties and turn off all three circuits, and yes it is there to protect the untrained from themselfs, that is why 70E came about. Most arc flash accidents come from somebody doing something stupid, and before somebody gets their underwear in a wad, I said most, not all.
 
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ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
MWBC on single pole breakers without handle ties are bad news.....
No they are not. We have a century of safe operation of MWBC. The code was, and should be, about safe installation and operation of electrical installations. Somewhere somebody working on a circuit is going to do something stupid no matter what kind it is.

As I said before- MWBC are not hard to recognize or work on safely. If you don't know what you are dealing with and get bit; that's a you problem.
 
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