Sharing Electrical service between 2 existing buildings
Sharing Electrical service between 2 existing buildings
(OP)
I am working on a UPS project. The ups is being fed by a 480 volt substation in building A and will be the source of critical power in building B. Both buildings have multiple substations fed by 2 ea. 12.4kv feeders.(Double ended subs) The buildings are joined by egress bridges and common hall ways, essentially 2 separate buildings. Grounding of the 2 buildings has been addressed, My question is a code concern about the 480 volt substation in building A feeding the critical power in building B. I cannot find any specific code section that would address this, yet I am concerned about the gray area of the building attachment: bridge and hallway as claim that the buildings are treated as one building.
Can anyone help me with my code/safety concerns of this design?
Thank you,
Michael
Can anyone help me with my code/safety concerns of this design?
Thank you,
Michael






RE: Sharing Electrical service between 2 existing buildings
For your installation, I'd strongly recommend discussing this with the local electrical inspector and working it out ahead of time.
It can probably be handled by appropriate signage, location of disconnecting means and interlocking.
RE: Sharing Electrical service between 2 existing buildings
Steve Wagner
RE: Sharing Electrical service between 2 existing buildings
The distance of the feeder is 400 feet, 100 ft. in building A and the rest in building B. There is an OCPD upstream at the UPS and a disconnect on the primary of the transformer.
The buildings have been bonded together, but I was concerned about the substation Xformer in building A and the possibility of a potential difference in building B due to the different HV feeders. This issue of mixing 2 individually / separately derived systems is my concern, however if someone else has additional information with respect to this design please chime in!
RE: Sharing Electrical service between 2 existing buildings
If on the other hand your concern as stated in your last post is in regards to potential differences, (on the grounded conductor?), I still feel you are ok. Since the second feed is to the critical loads in building B, I do not see where you would have both power systems present at any single piece of equipment.
In keeping with what DPC noted, it would still be a good idea and your AHJ would probably require that all circuits fed from the critical power system be properly identified including the location of the Main and downstream overcurrent protective devices and disconnects so that someone servicing these circuits does not assume that power has been disconnected if the building B main is opened.