Service Disconnect Question

[Jack Bright]

I am supplying an industrial shop with a 480 volt 3 phase service. The inside panel has a 400a main breaker. Am i required to install a disconnect outside?

 

[bphgravity]

The main service disconnecting means is required to be located per 230.70 of the NEC. Unless your local code modifies the NEC, the main disconnecting means is not required to be located outside of a building or structure.

 

[rcwilson]

Depends.

Cables to the 400A Main breaker would be Service Entrance Cables and the Main becomes a Service Entrance. Is the panel labled as suitable for Service Entrance? Does it have the proper grounding and bonding?

Do the cables and their installation comply with Article 230' s requirements for Service Entrance wiring?

If not, the external disconnect is probably the best solution.

 

[Jack Bright]

Thanks for the quick response. My original plan was to supply the 480 volt feed directly to the main breaker on the indoor panel. The plant manager requested today that we install a non-fused disconnect outside the building. He already has this disconnect on site. If I understand article 230 figure 230.1 correctly, everything past the disconnecting means becomes branch circuits, and therefore requires overcurrent protection. Wouldnt this make the non-fused disconnect unacceptable?

 

[augie47]

230.91 Requires the service overcurrent protection to be "an integral part of or immediately adjacent to"
the service disconnecting means. If your OCP does not meet that requirement the outside disconnect would not qualify as the "service" disconnect. You may still install it as a disconnect..it simply would not be the "service" disconnect.
You do need to keep in mind that NF switches normally have an AIC rating of 10k or less.


(side note: Is this supply actually a "service" supplied directly by the utility, or a feed from another building ? -)

 

[Jack Bright]

It is an actual service. Feed is from a utility type 12kv transformer that is owned by our company.