3 wire service, 250-32

[RRanger]

We have a 100A, 208V single phase service from a utility pole to a combo. meter/breaker on a pedestal with 3 wires. From there the service goes 400 feet underground to a camp with a 100A Main Breaker panel inside using 3 wires. We need 208V at the camp. Everything is in PVC.
We have 2 ground rods 10 feet apart at the meter and at the camp.
The AHJ has instructed us to tie the Neutral and the ground together at the meter and bond it to the enclosure. On the camp end, they want us to do the same. Is this correct or does the neutral need to be isolated from the grounds at the meter?

 

[jwelectric]

Re: 3 wire service, 250-32

The inspector is correct

 

[petersonra]

Re: 3 wire service, 250-32

alternately you could run a a ground wire out to the camp, then you would not need to bond the grd and neutral together there.

[ November 15, 2005, 03:44 PM: Message edited by: petersonra ]

 

[RRanger]

Re: 3 wire service, 250-32

OK thanks for the verification.

 

[stars13bars2]

Re: 3 wire service, 250-32

I just hate it when the inspector knows more about what I am doing than I do.

 

[james wuebker]

Re: 3 wire service, 250-32

No, From the meter/ breaker you should run 4 wires to your camps house 100amp panel. 2 hots,1 neutral and a ground. In that panel the neutral should be separate from your grounding wire. Your wire from your ground rods at the house should tie in with your ground wire that,s in your 100 amp panel. The neutrals and the ground wires shouldn't be together at your second panel.
Jim

 

[eprice]

Re: 3 wire service, 250-32

Originally posted by james wuebker: No, From the meter/ breaker you should run 4 wires to your camps house 100amp panel. 2 hots,1 neutral and a ground. In that panel the neutral should be separate from your grounding wire. Your wire from your ground rods at the house should tie in with your ground wire that,s in your 100 amp panel. The neutrals and the ground wires shouldn't be together at your second panel.
Jim

Jim,

What you describe conforms to 250.32(B)(1) and is a proper way to do it. What the original post describes (when corrected as discussed) conforms to 250.32(B)(2). Assuming there are no other metalic paths between the pole and the camp, this is also a proper way to do it.

 

[james wuebker]

Re: 3 wire service, 250-32

eprice, I agree with want you said but this could throw alot of people for a loop. Let's say I just ran steel conduit from each location just in the ground and the rest of the wire was buried. Why couldn't I just bond each pipe. One from the first disconnect(meter area) and bond the short pipe at the camp's 100 amp panel? The conduit would be protective from a fault then. I don't even like thinking about doing it this way but some people would. I still like to run 4 wires if there's a sub panel involved.
Jim

 

[allenwayne]

Re: 3 wire service, 250-32

Jim I have been taught that the first point of entry panel is the primary panel,any after that are subs and are to have grounds and neutrals seperated and the ground gets bonded not the neutral.I would have stood by that way of being taught but have since ben corrected.
It would be preferable the 1 st way,but we are not limited to that method as long as a 2nd set of ground rods we are creating an independantfault path for the 2nd panel

 

[james wuebker]

Re: 3 wire service, 250-32

Allen, I agree with you.
Jim

 

[hurk27]

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 ]