Meter-On-Pole and 250.32(B)

[NeoAmish]

Does a residence, with its own panel and main breaker, being fed by a meter-on-pole with its own disco, fall under 250.32(B)?

 

[raider1]

Yes it would.

Chris

 

[NeoAmish]

If there were no OCPD or other disco on the pole, would this then be SE instead of a feeder?

 

[raider1]

If there were no OCPD or other disco on the pole, would this then be SE instead of a feeder?

Correct.

Chris

 

[NeoAmish]

Ok, almost done with this line of thought.

Is there an actual engineering or safety reason for this? Or, is it merely semantics?

 

[raider1]

Once we have a service disconnecting means we now have established an equipment grounding system and the conductors from that point on are required to have an EGC pulled with the feeder.

Because the feeder now supplies a separate structure it is required taht the new structure have its own grounding electrode system that is connected to the EGC from the feeder.

Hope this helps.

Chris

 

[NeoAmish]

I may have been one of those kids that kept asking "why?"

It is required, but why?

My mind understands things like an EGC only being bonded at the main, not at subs, so that the EGC never shares current with the neutral, etc.


However, given two panels (one on a pole and one at the residence), if both of them are bonded to neutral, what does an extra ground wire between them do?

This may have veered from the NEC to grounding and bonding. If you would rather I posted the question in that sub-forum, I will.

 

[NeoAmish]

The above may have not been very clear. What I am getting at is, how does does the presence of a disco or OCPD upstream require an EGC? Without a disco on the pole, there would still be a metallic enclosure for the meter. Does the addition of an OCPD make it inherently less safe? Or, is it just semantics and word games involving where the service point is located?

This thread was interesting: http://forums.mikeholt.com/showthread.php?t=105409

 

[ceb58]

I may have been one of those kids that kept asking "why?"

It is required, but why?

My mind understands things like an EGC only being bonded at the main, not at subs, so that the EGC never shares current with the neutral, etc.


However, given two panels (one on a pole and one at the residence), if both of them are bonded to neutral, what does an extra ground wire between them do?

This may have veered from the NEC to grounding and bonding. If you would rather I posted the question in that sub-forum, I will.

The EGC and the neutral are not bonded together at the sub panels. The neutral is isolated from the non-current carrying metal parts that the EGC is bonded to.

 

[NeoAmish]

The EGC and the neutral are not bonded together at the sub panels. The neutral is isolated from the non-current carrying metal parts that the EGC is bonded to.

Right, I understand that.

Perhaps if I had more coffee I would be able to express myself more clearly.

I am merely bemused that the addition of an OCPD on the pole turns this into a feeder scenario vs a service entrance scenario.

As a 3 wire SE coming from a pole or ped, there is still the possibility for an open neutral to create a hazardous situation (if the neutral is bonded to the customer's panel). If the panel isn't bonded, then you run the risk of not being able to clear a GF just through the GEC alone.

it sounds like the poco's should be required to run an EGC all the time, every time.

 

[ActionDave]

As a 3 wire SE coming from a pole or ped, there is still the possibility for an open neutral to create a hazardous situation (if the neutral is bonded to the customer's panel). If the panel isn't bonded, then you run the risk of not being able to clear a GF just through the GEC alone.

it sounds like the poco's should be required to run an EGC all the time, every time.

But you would never run three wires from the meter pedestal to the house and not bond the neutral at the house. You would either run three wires and bond at the house or run four wires and bond at the meter. In the latter you do very little by running the fourth wire.

 

[NeoAmish]

But you would never run three wires from the meter pedestal to the house and not bond the neutral at the house. You would either run three wires and bond at the house or run four wires and bond at the meter. In the latter you do very little by running the fourth wire.

And not bonding the meter can would make it unlikely that a 200A OCPD could clear a GF to the can.

Many thanks to both raider1 and ActionDave for your input. I did have to draw a couple of diagrams to get my mind around it completely, but I see the reasoning for the 2008 change (I think).

(I still find the SP/SE boundary semantic interesting.)

 

[tortuga]

I may have been one of those kids that kept asking "why?"

It is required, but why?
...
However, given two panels (one on a pole and one at the residence), if both of them are bonded to neutral, what does an extra ground wire between them do?

If you run a 3 wire feeder from the meter base / main breaker at a pole instead of a 4 wire, then bond both neutrals to a GEC like a service you have created a parallel conductor.
The NEC is concerned about not creating a parallel neutral conductor. 1 conductor is the neutral the other is the earth. Other Parallel conductors are phone and cable neutrals (or shields). Neutral current will flow on all of these that are bonded at the pole and house.
(I have herd of a melted coax shield glowing red due to a open neutral at a service)

You can detect this by putting a clamp on ammeter around a GEC. In classic "row housing" and town houses where all the metal service water pipes are bonded in the basements and the pipe just runs through the basements you can actually measure neutral current on the water pipe.
Here is more reading on the topic:
http://www.iaei.org/magazine/2003/1...ircle-on-parallel-paths-and-end-on-a-tangent/

http://grouper.ieee.org/groups/td/dist/documents/emfurd.pdf

I think Mike Holt has some more nice illustrations of on line somewhere.

 

[ptonsparky]

Recently looked at a project that included a POCO installed meter/disconnect. The disconnect had a label indicating it was a Service Disconnect. Hadn't seen one of those before. My dilema was to ignore that disconnect as we, in NE, are generally allowed to do, and string 3 wire ACSR to another pole or run 4 wire. That decision was taken out of my hands when the owner talked the POCO into providing the overhead and pole. Anyone want to bet on if it will be 3 or 4 wire?

Now that the POCO is providing the items, the Pump installer will provide and install all the electrical. real deal.