Re: 3 wire service, 250-32
Jim From how I see it, or should I say the way I feel this should be is:
The pole that the meter and disconnect in mounted on by definition is a structure, But there is no where in the NEC that it is required to have a disconnect and or OCPD's to protect a pole that service conductors do not enter. So if the disconnect is not required then I feel that the service conductors continue past this point until they reach the required disconnect at the building which is required To me it seems that even with a mobile home they allow this to a disconnect before requiring 4-wires, look at 550.33(A) exception.
There is no need for a disconnect at the pole other than if the supplying utility ask for one but then to me its only there to allow for the change out of the meter and I think it would be called a meter disconnect, which is allowed to be ahead of the main service disconnect (230.82(2)).
This would move the service disconnect of the building to the building which would have to meet the requirements of service equipment. Which the building would be required to have a disconnect anyway.
Now for the stickler:
250.24 requires that the grounding electrode conductor to be connected to the grounded conductor at the service disconnect, this would require that the GEC be run all the way out to the pole, That would render it useless for a lightning strike.
While I'm saying all this I am an advocate to separate isolated neutral all the way from the transformer, but only if the service EGC was sized the same as the grounded conductor or ungrounded conductor, The reason is I feel this way is, an EGC sized by table 250.122 would allow a very large fault current voltage drop to be present upon all that is bonded to it when any ground fault were to occur. This would allow a shock hazard to anyone that was touching the grounding and standing on earth, think of this: A child bending over getting a drink of water out of the hose bib when daddy, working in the garage accidentally pulls out the cord shorting the hot to the EGC or case of the welder, I won't take the time now to figure what this would cause the voltage difference that this child would be hit by, but I think it would hurt him to say the least.
Sorry for the long windedness.
[ November 18, 2005, 12:41 AM: Message edited by: hurk27 ]