Tapping An Existing Switchboard Bus - OCPD Requirements

[rjken1969]

I'm doing some work at an existing facility. It's a high rise mixed used building with multiple building and tenant services being fed through a single 2500A breaker, prior to utility metering. It's an older facility, and the electrical system is somewhat haphazard. The owner wants to replace a large steam absorption chiller with an electrical chiller. This means a new 600A feed from the existing system.

The system has capacity for the feed, but it will require tapping the bus and locating a new FDS in an electrical room that has no room for expansion. What code section outlines the requirements for this type of modification? I'm tapping after a main breaker, but need to locate the new FDS remotely, it appears that the FDS will have to be located outside of the electric room. Is this allowed by the NEC?

 

[Smart $]

FDS = ???

TTBOMK there is no requirement for electrical distribution equipment to be located in a specific room. The only related requirement I can think of offhand is a service disconnecting means cannot be located in a bathroom.

 

[rjken1969]

FDS = Fused Disconnect Switch

 

[david luchini]

What code section outlines the requirements for this type of modification?

See 240.21(B).

 

[rjken1969]

I'm looking at 240.21, and it appears that it applies to feeders. Also, according to this, it looks like it's not an issue. Does this apply to a tap that will be made within a switchboard section, placing the taps on the phase busses?

 

[david luchini]

I'm looking at 240.21, and it appears that it applies to feeders. Also, according to this, it looks like it's not an issue. Does this apply to a tap that will be made within a switchboard section, placing the taps on the phase busses?

Yes, all conductors after the main breaker, but before the final Branch circuit overcurrent devices are feeders. Tapping the main switchboard bus must be done in accordance with the feeder tap rules.

 

[PEDRO ESCOVILLA]

if the buss bars dont already have holes drilled from the factory, you wil probably void the listing of the equipment. just a heads up. quessing the buss bars re tapped already (not a field modification)