Ground rod at non-service disconnect switch?

[rrc14]

Working on a project where we are installing a 150A, 480V, 3-phase feeder, (3 conductors and a ground) from a MCC over to another building. This feeder is being terminated to a safety disconnect switch mounted on the exterior wall of the building. The question that I have is does this safety disconnect switch need to be tied in to a ground rod at the building? It is not a separately derived power source. Looking over Article 250 in NEC and it is still not clear to me yet. Any comments would be appreciated. Thanks,

 

[bphgravity]

Yes. A grounding electrode system at the separate sdtructure is required. See 250.32 of the NEC.

 

[infinity]

Is this the only feeder to the building?

 

[rrc14]

Yes, it is the only feeder for the building. The feeder provides electricity to a 480V-120V/208Y step-down transformer, which then feeds a panelboard. The secondary of the step-down transformer is grounded to a ground rod.

I was unclear if the 480V feeder (3 conductors & ground) needed to be grouded to a ground rod since it wasn't a separtely derived system.

 

[nakulak]

225.30
250.50

 

[philly]

If an EGC is run with the feeders from the MCC than what is the purpose for providing a seperate grounding electrode at the building disconnect. I know the code requires it, but what purpose does this serve?

I know ground fault current flowing through ground will not be large enough to trip an OCPD so is this grounding electrode to help eliminate touch potential?

 

[don_resqcapt19]

If an EGC is run with the feeders from the MCC than what is the purpose for providing a seperate grounding electrode at the building disconnect. I know the code requires it, but what purpose does this serve?

Just like at a service the grounding electrode is to provide some protection from lightning and contact with higher voltage systems.

I know ground fault current flowing through ground will not be large enough to trip an OCPD so is this grounding electrode to help eliminate touch potential?

A grounding electrode does little to eliminate step and touch potentials.

 

[charlie b]

I was unclear if the 480V feeder (3 conductors & ground) needed to be grouded to a ground rod since it wasn't a separtely derived system.

It is not the feeder that brings into play the requirement for a ground rod. It is the building itself. Each structure that has a source of electrical power must have a grounding electrode.

 

[Jesse7623]

If an EGC is run with the feeders from the MCC than what is the purpose for providing a seperate grounding electrode at the building disconnect. I know the code requires it, but what purpose does this serve?

I know ground fault current flowing through ground will not be large enough to trip an OCPD so is this grounding electrode to help eliminate touch potential?

Lightning.