Branch Circuits Article 210

[dennis323]

My questions refers to the following statement;

All conductors of a MWBC must originate from the same panelboard [210.4(A)]. Each MWBC must have a means to simultaneously disconnect all ungrounded conductors where the MWBC originates [210.4(B)]. You can use individual single-pole circuit breakers with handle ties identified for the purpose [240.15(B)(1)].

How does this apply to computer room power whips. If the whips contain MWBC's in the same raceway (sealtite) but have seperate boxes with seperate devices that feed different loads, Is it a requirement to de-energized all circuits contained in the same raceway?

 

[tom baker]

The requirement is to deenergize all hots of a MWBC at the same time.

 

[GoldDigger]

But if you break out a separate non-MWBC circuit from an MWBC, you can certainly put an interrupting device in that branch which does not reach back and disconnect all the other branches.
The heart of the requirement is that if at some point you try to open the circuit, you want to make sure that you have removed all current sources for the *shared* neutral.
Once the neutral at a disconnect is no longer shared, the requirement goes away.
JMO.

Tapatalk!

 

[charlie b]

And to take it one step further, if there are two or more MWBCs in the same raceway, you don't have to be able to turn them all off at the same time. You can arrange the breakers and/or handle ties such that all of the hots associated with one MWBC are turned off at the same time, while the other MWBCs in the same raceway remain energized. Keep in mind that if you have that many conductors in the same raceway, you will have to deal with derating issues.

 

[ActionDave]

... Keep in mind that if you have that many conductors in the same raceway, you will have to deal with derating issues.

And in turn brings us back to using MWBC as a good way to deal with derating issues. Also a good way to save wire, time, money, room in the panel.....

 

[Scott.Haldiman]

watch those neutrals.

watch those neutrals.

And to take it one step further, if there are two or more MWBCs in the same raceway, you don't have to be able to turn them all off at the same time. You can arrange the breakers and/or handle ties such that all of the hots associated with one MWBC are turned off at the same time, while the other MWBCs in the same raceway remain energized. Keep in mind that if you have that many conductors in the same raceway, you will have to deal with derating issues.

Just be careful to maintain constant identification of which neutral goes to which set of "hots". Nothing worse than thinking you are de-energized, and being surprised! Always test the neutrals for voltage and amperage, even if the 3 pole breaker is off. You never know who made the final connections and if they are as diligent as they need to be