How do you handle this situation

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dahualin

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I have a project to add a small office building (around 3000 SQFT) 200 feet away from a big existing building. The existing building has an existing electrical yard with switchboard, generators, ATS cabinet, and panels in it. The switchboard has ground fault protection to each distribution circuit breaker. I am adding one distribution circuit breaker with ground fault protection in the existing switchboard and feed to the new office building. My question is "Do I need to treat the feeder to the new office building as electrical service?" . If it is a feeder, I shall run 3 phases + 1 neutral + 1 ground wires to new office. If it is a service, I shall run 3 phases + 1 neutral wires to new office, and install grounding system and bond them to service panelboard's main ground bar with neutral bar. Which way is correct? Thanks.:-?
 
You will need a neutral and ground alond with any ungrounded conductors. You will also need the required grounding electrodes and disconnects.
 
I agree with the others and the NEC sections you need to look at are 225.30 > 225.40 and 250.32

dahualin said:
My question is "Do I need to treat the feeder to the new office building as electrical service?"
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No, the electrical 'service' can only be provided by a utility and that service in this case stops at the service disconnecting means of the property.

See 'Service' in Article 100
 
5 or 4 conductors between buildings when the system is a feeder will depend on what code cycle you are following. If you are referencing the 2008, you will be required to install 5 conductors.
If you are referencing a code cycle before the 2008 NEC you have a choice as to 4 or 5 conductors.
 
If you have ground fault protection up stream would bonding the neutral and ground at the new office cause it to trip. I do not think you can bond after the ground fault. Run it as 5 wire and be ready for the future
 
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