bonding

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Petet55

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The building I am working in has 480v busduct overhead I am installing a 3phase 208v pannel we hung the transformer at the transformer we bonded the ground and the neutral and grounded in to the steel I-beam support then we installed the 208 pannel. Should the ground and the nuetral be bonded at the pannel or not?

thanks Petet55
 
kjless said:
this always threw me off too. you can either bond it at the transformer or the panel
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It's similar to the pre-2008 NEC rule about omitting a separare EGC in the feeder to a detached building, as long as there were no parallel metallic pathways. The building steel would be such a path with the neutral nonded twice.

Or, think of it as a little transformer-and-house supply and service that will only get one ground rod.
 
because you are tecnicaly creating a new service the neutral and the ground should now be attached in the panel
 
VICC said:
because you are tecnicaly creating a new service the neutral and the ground should now be attached in the panel
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...or at the transformer.

there is no "written in stone" rule on this ~ ladies' choice :smile:

250.30(A)(1) as Pierre pointed out previously.
 
VICC said:
because you are tecnicaly creating a new service the neutral and the ground should now be attached in the panel
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The term used in the highlighted portion is not correct.

You will find the definitions of Service and Separately Derived System (SDS) in Article 100.

The key in the definition of a Service is "from the serving utility". If the supply is not from a utility, it is not a service.
Since the supply is from a transformer, it is most likely a SDS. A separately derived system has no "circuit conductors" that are common from the primary side to the secondary side. An equipment ground conductor is not considered a "circuit conductor."
 
Pierre C Belarge said:
The term used in the highlighted portion is not correct.

You will find the definitions of Service and Separately Derived System (SDS) in Article 100.

The key in the definition of a Service is "from the serving utility". If the supply is not from a utility, it is not a service.
Since the supply is from a transformer, it is most likely a SDS. A separately derived system has no "circuit conductors" that are common from the primary side to the secondary side. An equipment ground conductor is not considered a "circuit conductor."
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I would agree. It's better to say that the SDS is like a new service because there are similarities but also differences. One major difference is that the SDS does not have the same bonding requirements that apply to service raceways.
 
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