3+1 Systems Furniture - powered from two panelboards.

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The owner has selected a 3+1 wiring package for the systems furniture. The systems furniture has an internal wiring harness with 3 circuits sharing a neutral and ground wire PLUS a separate power circuit with a dedicated neutral and dedicated ground for that circuit. The concept is for the dedicated circuit to be powered from a UPS and serve critical loads with the other three circuits supplied from a standard panelboard to serve the non critical loads.

The electrician is balking at installing the system citing NEC 210.4's requirement that "All conductors of a multiwire branch circuit shall originate from the same panelboard or similiar distribution equipment." NEC 210.4(B) further requires all multiwire branch wiring must be disconnected from a single point.

As I interpret the code we have one multiwire branch circuit and a single separate circuit powering the workstations. The electrician says that since they are connected to the same "whip" which then plus into the workstation it is a single multiwire circuit and all of the circuits must be disconnected together and be supplied from the same panelboard.

What is the board's opinion?
 

augie47

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Are the partitions free standing or fastened to the building surface ??
 

augie47

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Do not have book right now. Why does this make a difference as far as what makes a MWBC?
I originally thought that it did but in doing the research the difference is with free standing cord and plug connected.,,
With that out of the way, back to the OP, IMO the multi-wire circuits would need simultaneous disconnecting bt I see no requirement for that to extend to the individual circuit.
 

highlegdelta

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One could argue that 210.7 would require the multi-wire branch circuit and the individual branch circuit to be opened simultaneously


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texie

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Fort Collins, Colorado
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Electrician, Contractor, Inspector
The owner has selected a 3+1 wiring package for the systems furniture. The systems furniture has an internal wiring harness with 3 circuits sharing a neutral and ground wire PLUS a separate power circuit with a dedicated neutral and dedicated ground for that circuit. The concept is for the dedicated circuit to be powered from a UPS and serve critical loads with the other three circuits supplied from a standard panelboard to serve the non critical loads.

The electrician is balking at installing the system citing NEC 210.4's requirement that "All conductors of a multiwire branch circuit shall originate from the same panelboard or similiar distribution equipment." NEC 210.4(B) further requires all multiwire branch wiring must be disconnected from a single point.

As I interpret the code we have one multiwire branch circuit and a single separate circuit powering the workstations. The electrician says that since they are connected to the same "whip" which then plus into the workstation it is a single multiwire circuit and all of the circuits must be disconnected together and be supplied from the same panelboard.

What is the board's opinion?

I agree with infinity. This is pure nonsense. By that logic if you were to have multiple circuits in the same raceway you would need simultaneous disconnecting.
 
One could argue that 210.7 would require the multi-wire branch circuit and the individual branch circuit to be opened simultaneously


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In this case the workstations are free standing and are not connected to a wall or bolted to the floor. In order for all 4 circuits to be de-energize simultaneously they would need to be supplied from the same panelboard. The client would like the critical equipment to be supplied from a UPS which feeds a separate panel.
 

highlegdelta

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Location
US
How so? Are they on the same yoke or mounting strap?

Well I wouldn't make the argument personally but you are connecting your base feed whip to a single point on that blank plate with the hole drilled into. I feel like if an AHJ decided that blank plate qualifies as a yoke or mounting strap, then there is a solid chance that it would be very difficult to prove that it isn't.

Again, I don't agree with that interpretation and am just playing devils advocate.


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highlegdelta

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In this case the workstations are free standing and are not connected to a wall or bolted to the floor. In order for all 4 circuits to be de-energize simultaneously they would need to be supplied from the same panelboard. The client would like the critical equipment to be supplied from a UPS which feeds a separate panel.

I don't think it should have to be simultaneously disconnected. If he is hell bent on this, I'd suggest recommending a label that says its fed from multiple sources.


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ActionDave

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Well I wouldn't make the argument personally but you are connecting your base feed whip to a single point on that blank plate with the hole drilled into. I feel like if an AHJ decided that blank plate qualifies as a yoke or mounting strap, then there is a solid chance that it would be very difficult to prove that it isn't.

Again, I don't agree with that interpretation and am just playing devils advocate.


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Pretty sure the definition of a yolk is limited to a device so the inspector would not be able to make that argument.
 

david

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Pennsylvania
I agree with infinity. This is pure nonsense. By that logic if you were to have multiple circuits in the same raceway you would need simultaneous disconnecting.

The UPS circuit does not need to disconnect with the multiwire circuit. not sure i understand your comment about the mulltiwire circuit. It sounds like your saying the multiwire circuit does not need one throw to disconnect.
 

charlie b

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Lockport, IL
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The electrician says that since they are connected to the same "whip" which then plus into the workstation it is a single multiwire circuit and all of the circuits must be disconnected together and be supplied from the same panelboard.
The electrician is wrong. Look at the definition of MWBC. It has nothing to do with the load connections. It is all about where the power comes from. The whip is not relevant to the question of what is, and what is not, a MWBC.

 

infinity

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The electrician is wrong. Look at the definition of MWBC. It has nothing to do with the load connections. It is all about where the power comes from. The whip is not relevant to the question of what is, and what is not, a MWBC.


I agree but in earlier editions of the NEC (before the requirement to handle tie all MWBC's serving CB's together) there was a requirement for a handle tie or multi-pole CB's if the MWBC served a single yoke or strap so the load connections then were relevant.
 

texie

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Location
Fort Collins, Colorado
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Electrician, Contractor, Inspector
The UPS circuit does not need to disconnect with the multiwire circuit. not sure i understand your comment about the mulltiwire circuit. It sounds like your saying the multiwire circuit does not need one throw to disconnect.

I think you and I agree. Yes, there is 1 MWBC that needs a handle tie and an additional circuit that is unrelated. I was trying to point out that these 2 circuits do not need ties together just because they are in the same whip.
 
Thanks for all of your thoughts. Against my advice the owner directed the contractor to wire all of the furniture circuits from the UPS and put a tie across 5 circuit breakers. In the end the owners logic was that it was the fast solution, the UPS was lightly loaded, and we were "only" adding 6 more circuits supplying 15 workstations.

Another case where expedience trumped logic, IMHO.
 

don_resqcapt19

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Illinois
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Thanks for all of your thoughts. Against my advice the owner directed the contractor to wire all of the furniture circuits from the UPS and put atie across 5 circuit breakers. In the end the owners logic was that it was the fast solution, the UPS was lightly loaded, and we were "only" adding 6 more circuits supplying 15 workstations.

Another case where expedience trumped logic, IMHO.
Are there any handle ties that are identified for use with five breakers?
 
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