Offset Nipple between Meter and Disco

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flashlight

Senior Member
Location
NY, NY
Inspector just made us open a meter to put a bonding
jumper between the meter pan and service disco.

His reason ? The meter pan was joined to the service disco with
an offset nipple. Nipple had locknut and MIGB with bonding jumper to enclosure and neutral, both inside disco and inside meter enclosure. Inspector said since offset nipple has shoulders on outside of box, instead of threads and another locknut, it doesn't sufficiently bond the 2 enclosures.

I say they are bonded through the locknuts and MIGBs at either end of nipple that are bonded to enclosures. Boss agrees, but said change it anyway since it's not worth fighting with these guys.

Is inspector correct ?
 

mcclary's electrical

Senior Member
Location
VA
In VA, I deal with 3 power company's. (2) of the (3) WOULD require the bond you are speaking, the 3rd, would remove the bond even if you, or the inspector said other wise. So, power companies can't even agree on this.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
I would think the neutral is adequately bonding the meter to the disconnect, just as it would with a PVC nipple. I could see wanting to bond the nipple with a bonding locknut or bushing.
 

quogueelectric

Senior Member
Location
new york
Inspector just made us open a meter to put a bonding
jumper between the meter pan and service disco.

His reason ? The meter pan was joined to the service disco with
an offset nipple. Nipple had locknut and MIGB with bonding jumper to enclosure and neutral, both inside disco and inside meter enclosure. Inspector said since offset nipple has shoulders on outside of box, instead of threads and another locknut, it doesn't sufficiently bond the 2 enclosures.

I say they are bonded through the locknuts and MIGBs at either end of nipple that are bonded to enclosures. Boss agrees, but said change it anyway since it's not worth fighting with these guys.

Is inspector correct ?

If the migb doesn't bond it then what does?? It is hard to find good help these days. I too would just give him what he wanted and get paid.
 

e57

Senior Member
There are also a few other places POCO, AHJ that feel the die cast material an off-set are made of have insufficient grounding/bonding properties, and also some that would feel it offered inadequate protection of the conductors. They are pretty brittle...

Also - if the opening for this nipple - if above the service conductors may not be acceptable for sealing out water as described. A sealing lock-nut or Myers hub may be required...

But - since the nipple is metallic, and both enclosures have a neutral bond - it is then a parallel path for neutral current. Most will say it only needs to be bonded on one end for fault current - and since most POCO's will not allow a "bonding bushing" and especially the conductor to it on their side at the meter - which is the path any fault current must follow - which is also parallel with the neutral as well - it is the same path... (All available paths... This has been argued before.... ;) I don't think anyone won...)

Anyway - the NEC is pretty vague and steers clear of meter enclosures - and basically what-ever your POCO wants goes in there. Even if it is a contradiction to the wording of 250.90, and 250.92A If you put a bonding bushing in there - it is the conductor to it they freak out about - grounded wires - the bonding jumper to the bushing and enclosure...

However - a self grounding lock-nut, like those found on many Myers type hubs are often acceptable. Or a grounding lock-nut by itself... As there are no additional grounding conductors in the enclosure. It also shares the same UL file number with grounding bushings. However if you look at what that product is made for - "For use with Rigid/IMC Conduit." Use of that on some crappy mealy tin off-set nipple might destroy it - or any other die-cast connector for that matter...

It should also be said that 'regular' lock-nuts are not accepted by the NEC for grounding of conduits for service conductors... See 250.92B
 

flashlight

Senior Member
Location
NY, NY
Out of curiosity, why did you bond the nipple on Both sides?

This is common practice around here. BTW, it was the city inspector, not the POCO, who asked for the jumper. The POCO inspector was fine with it.

Also, owner of company, 37 years in trade, said he had not been asked to do this before.

Thanks, everyone, for weighing in.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
This is common practice around here. BTW, it was the city inspector, not the POCO, who asked for the jumper. The POCO inspector was fine with it.

Also, owner of company, 37 years in trade, said he had not been asked to do this before.

Thanks, everyone, for weighing in.

It obvious that the inspector didn't know what he was talking about.

Inspector said since offset nipple has shoulders on outside of box, instead of threads and another locknut, it doesn't sufficiently bond the 2 enclosures.

The metallic service raceway, in this case the nipple, is not there to make a continuous path between the two enclosures. The neutral is already bonded to both enclosures.
 

mcclary's electrical

Senior Member
Location
VA
It obvious that the inspector didn't know what he was talking about.



The metallic service raceway, in this case the nipple, is not there to make a continuous path between the two enclosures. The neutral is already bonded to both enclosures.



I agree, and Dominion agrees, but CVEC, and Rappahannock BOTH DEMAND a #6 solid bond to their meter bases. They will not hook to it if it is not there, and the inspectors around here know what the power company wants and enforce that. If it's a Dominion base, they'll fail you for INSTALLING the bond, if it's a CVEC or Rapp. Base, they'll fail you for NOT INSTALLING the bond. You would think power companies could come to an agreement on this.
 

e57

Senior Member
The metallic service raceway, in this case the nipple, is not there to make a continuous path between the two enclosures. The neutral is already bonded to both enclosures.
I have seen this as an interpretive issue - as 250.92B says 'electrical continuity - service equipment, raceways and enclosures by the following methods...' Bonding one end only is continuity to only one side in those allowed methods - and away from the current path for that matter. Fault current will take both paths in this case - not just the bonded end alone. And nowhere in that code does it say only bond one end of a raceway. Both enclosures bonded - bond conduit to one... The way many interpret this would allow it - the way some others see it - no it should be both... I see it as both, but POCO's and their fear of bonding jumpers being in the way while they might be moving live conductors in a small space get them all bent out of shape - which is why it is industry practice in many areas to just do one side - I'm sure they would prefer the cans not be intentionally grounded at all.... ;)
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
I have seen this as an interpretive issue - as 250.92B says 'electrical continuity - service equipment, raceways and enclosures by the following methods...' Bonding one end only is continuity to only one side in those allowed methods - and away from the current path for that matter. Fault current will take both paths in this case - not just the bonded end alone. And nowhere in that code does it say only bond one end of a raceway. Both enclosures bonded - bond conduit to one... The way many interpret this would allow it - the way some others see it - no it should be both... I see it as both, but POCO's and their fear of bonding jumpers being in the way while they might be moving live conductors in a small space get them all bent out of shape - which is why it is industry practice in many areas to just do one side - I'm sure they would prefer the cans not be intentionally grounded at all.... ;)

The electrical continuity is provided by bonding the neutral in both places. This makes using the metallic nipple for continuity unnecessary. If you had a PVC nipple you would rely on the neutral bonding for the continuity. The same rationale applies to the metallic nipple. Since it's a service raceway it requires bonding beyond standard locknuts. This can be accomplished by using a bonding bushing on one end.
 

ty

Senior Member
The electrical continuity is provided by bonding the neutral in both places. This makes using the metallic nipple for continuity unnecessary. If you had a PVC nipple you would rely on the neutral bonding for the continuity. The same rationale applies to the metallic nipple. Since it's a service raceway it requires bonding beyond standard locknuts. This can be accomplished by using a bonding bushing on one end.

i agree...
 

e57

Senior Member
The electrical continuity is provided by bonding the neutral in both places. This makes using the metallic nipple for continuity unnecessary. If you had a PVC nipple you would rely on the neutral bonding for the continuity. The same rationale applies to the metallic nipple. Since it's a service raceway it requires bonding beyond standard locknuts. This can be accomplished by using a bonding bushing on one end.
Oh I knew the can of worms was being opened.... I know the interpretation many base it on etc.... And the standard practice people have been doing for years..... But it is not what the wording of the code says IMO... (yes if it were a PVC raceway - non-issue - bond the neutral in each can - done) And I have agreed to dis-agree on this in the past - which does not mean I changed my mind about it right or wrong... (and as you can see a few posts back - other places require both ends are they wrong - NO - just the way they both read, interpret and allow it....)

A few points I have issue with the one-end method:
  • Nowhere in this section does it specifically say "one end" or anything to that effect - IMO nor does it elude to it either. Many would point to 250.92(B)1 - no mention of a raceway there... Just the equipment enclosures...
  • From your point of veiw you might also say that nowhere does it say both ends... However - the enclosures at both ends are bonded because of 250.92(B)1 - and nowhere in the items below it does it say to pick one end - or which enclosure. 250.92(A) specifically say all of these items need to be bonded "together" - one side over the other is not "together' enough for me...
  • Since each enclosure is bonded to the grounded service conductor - the metallic raceway is going to carry neutral current whether you like it or not - it is a parallel conductor of the grounded conductor. (*If you want to have some fun on a boring day - load up just one leg at a time of the service - measure current on the hot leg, and then on the neutral and find out just how much of a percentage of the neutral current that is... The neutral will be less than the hot leg - that difference is going through the conduit - known as "Objectionable current" see 240.6 which would lead one to believe they should isolate one end - but they can't, or could they - is a product made for such? Also - See 250.4 to create an "Effective ground fault current path" - back to bonding both ends...;))
  • Downstream fault current - same as above
  • Now - the kicker - if in the event of a fault actually inside the nipple between the two enclosures - the fault may disconnect or damage grounded service conductor inside it. If only bonded downstream from the fault, this current then only has one non-qualified way to go - back to the source through the regular ol' locknut at the meter base.
FWIW - I also see this as no different as the reasoning behind bonding both ends as one would in 250.64(E)
 
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