George Little Member posted 02-16-2005 04:06 PM
Tom- Very briefly- The transfer switch is Service Rated- It is the disconnect for the "feeder" from the other building- There is no EGC with the feeder so there is no paralleling of the neutral. the Grounding electrode for the utility and the "feeder" are one and the same in the house. The only question I have is-Since I don't need an EGC run with my feeder to a detached building when I come off the Service - Do I need one if I run from my detached building to my house off my generator. If I do then you are correct.
George
No matter how many wires you use in the derived system's supply conductors to the house you still have to avoid re grounding the service supplied feeder neutral that runs from the Service Equipment to the Emergency Panel in the house. There are two ways to avoid this. One is to use a three pole switch so that the required grounding electrode conductor to your building disconnecting means; in this case the transfer switch; is not bonded to the service supplied feeder's neutral. The other would be to not bond the derived system neutral to the building disconnecting means. Remedy two is not available to you because you ran only three conductors from your derived system. You have to bond the derived system neutral to ground at the house as required in 250.32 (B) (2). If the generator does not supply any load, including any receptacles on the generator itself, at the garage then you can argue that 250.32 does not apply. You can also argue that it does not apply because the generator is not a service. But if you look at how transformers located outdoors are treated by 250.24 Grounding Service-Supplied Alternating-Current Systems, (A) System Grounding, (2) Outdoor Transformer, you will see that the intent of the code is to bond the neutral of the supply to buildings both at the outdoor source and at the disconnecting means. I guess my point is that if you are going to apply the rules for two or more buildings... to a derived system then you should apply them consistently.
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Tom H
