Seperately derived neutrals

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C

CMU

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I have 2 seperate buildings(A and B) both supplied by 4160 volts and transformed down to 208/120.
I have to feed a panel in building "B" from a normal emergency panel in building "A"
Is it OK to tie the neutral from building "A" to the neutral in building "B"?
I'm no engineer so I don't know how the unblanced currents or fault currents would be affected.

Thanks
 
Smart $

Smart $

Esteemed Member
Location
Ohio
You don't need an engineer to answer that question. You already see the answer you got from one engineer... :lol:

You especially do not tie the neutral of one system to another. In many cases neutral's are effectively bonded together because of grounding requirements... but that is Code-wise NOT tying them together. All neutral's in building B supplied with the neutral of a system originating in Building A get tied to that neutral and none other. The GES of all Building B systems will be common. The GES's of both buildings will be bonded through the EGC of the emergency feeder.
 
T

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
CMU said:
I have 2 seperate buildings(A and B) both supplied by 4160 volts and transformed down to 208/120.
I have to feed a panel in building "B" from a normal emergency panel in building "A"
Is it OK to tie the neutral from building "A" to the neutral in building "B"?
I'm no engineer so I don't know how the unblanced currents or fault currents would be affected.

Thanks
Click to expand...

Since you mention "emergency" I'm assuming that this is an Art. 700 system which would mean that the ATS for building B would have to be located in building B. An emergency feeder would come from building A emergency system to supply this ATS.
That in turn will require a switched neutral ATS in building B as you can't tie the neutrals together from 2 separately derived systems, as would be the case with a solid neutral ATS used in this type of installation.
 
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C

CMU

Member
That is what I thought. It was not really a code question more of a safety question. We DO NOT have a 4 pole ATS in Building B to facilitate a switched neutral.
That being said I will just disconnect all normal power from the ATS in building "B" including the neutral and supply those 3 panels from the NE panel in building "A" The 3 panels in building "B" are for lighting only with Only single phase loads. This is supposedly temporary until building "B" gets a new genset but We all know how "temporary" goes.

Thanks for the input!
 
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