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#96211 - 11/10/05 07:03 AM service bonding  
shortcircuit  Offline
Member
Joined: Jun 2004
Posts: 608
massachusetts
I've installed a 10ft section of ridged conduit for the riser at the street pole for protection of 200amp 4/0 URD AL service conductors for an underground service. This isolated section is required to be bonded according to 250.92

To bond in this situation I would need to:

1)Install a bonding bushing on the RMC and run a #4 bond wire to a 8ft ground rod at the base of the pole...

2) Install a bonding bushing on the RMC and leave the #4 bond wire long enough for the Utility Company to run it up the pole to connect to the grounded service conductor...

3) Run a #4 bonding wire with the underground lateral and connect to the bonding bushing on the pole end and connect in the meter at the house end to the grounded service conductor...

How do you bond in this case?

shortcircuit


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#96212 - 11/10/05 07:26 AM Re: service bonding  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Cool question.

First is this section of raceway covered by the NEC? I doubt it.

I do agree common sense says it needs to be bonded.

Quote
1)Install a bonding bushing on the RMC and run a #4 bond wire to a 8ft ground rod at the base of the pole...


Pointless ineffective waste of time.

Quote
2) Install a bonding bushing on the RMC and leave the #4 bond wire long enough for the Utility Company to run it up the pole to connect to the grounded service conductor...


That could work if the POCO is agreeable.

Quote
3) Run a #4 bonding wire with the underground lateral and connect to the bonding bushing on the pole end and connect in the meter at the house end to the grounded service conductor...


That would also work but IMO a waste of materials and adding unnecessary length and impedance to the bonding conductor.

Here is my suggestion, install bonding bushing and install a short bonding jumper from the bonding to the grounded conductor as it emerges from the GRC.

Simply use a connector that you can easily tap the grounded conductor with. H-Tap would be nice.

Quote
250.142 Use of Grounded Circuit Conductor for Grounding Equipment.

(A) Supply-Side Equipment. A grounded circuit conductor shall be permitted to ground non–current-carrying metal parts of equipment, [b]raceways[/b, and other enclosures at any of the following locations:

(1)On the supply side or within the enclosure of the ac service-disconnecting means


Bob


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#96213 - 11/10/05 06:32 PM Re: service bonding  
Electricmanscott  Offline
Member
Joined: Jan 2002
Posts: 1,457
Holden, MA USA
The answer should be #2. Check with the power co.


#96214 - 11/10/05 09:47 PM Re: service bonding  
shortcircuit  Offline
Member
Joined: Jun 2004
Posts: 608
massachusetts
I did some reading of NSTAR's year 2001 "requirements for electric service" searching for a bonding requirement for RMC as a riser conduit up the company's (Nstar) pole.

In the manual,(for sparky's in Massachusetts) on page 113, note #3 to sketch 6 says: "RMC requires a grounding connector for connection of #4 CU wire." when used as riser pipe on a Nstar pole.

Now, I am well aware that the ground rod, as I described in my first post, is useless for bonding this RMC from reading posts here for some time now, but thought I would list it as a choice. But I have seen many a stick of RMC grounded in this manner...which seems to serve no purpose at all.

Also,driving around today, I saw many RMC riser pipes with the bonding bushing, but no #4 bond wire installed at all. Apparently installed by the electrician, but not bonded by the utility company.

Note that any part of the installation on public property including the RMC riser, becomes property of Nstar once energized.

Iwire, I like your suggestion for bonding this isolated section of RMC and will try to use it. I will run it by Nstar engineers first.

Electricmanscott, the exception to 250.102(E) directly addresses this installation of RMC as a riser and answer #2 of my original post as a bonding method. I will also run this by Nstar.

Thanks for your input on this.

shortcircuit


#96215 - 11/10/05 10:39 PM Re: service bonding  
Electricmanscott  Offline
Member
Joined: Jan 2002
Posts: 1,457
Holden, MA USA
I always seem to work in towns with municipal light departments where almost anything goes. Usually more rural installations where sched 80 pvc is used for risers so I have not had to deal with this at all.
But as I said #2 seem to be the correct way to go.


#96216 - 11/11/05 04:09 PM Re: service bonding  
jes  Offline
Member
Joined: Jul 2002
Posts: 103
CT
Here in CT the utility requires an RMC sweep capped at the top, no riser. They clearly state in their 'Information & Requirements' book that THEY are responsible for the grounding/bonding of the rigid sweep at the pole end.



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