grounding bushings question

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I looked at the above-mentioned code sections, and am left with a related question. Situation is a residential service with a main disconnect that has a threaded hub bolted to the top of it, and a close nipple that is lock-nutted to the bottom of the meter base through the largest KO, so there are no concentric rings left. The neutral conductor is bonded in both enclosures, so the nipple is merely the service raceway.

So, must a bonding locknut or bushing be installed on the top of the nipple? We're not allowed to land any GECs in meter bases since we're sealed out of them and they can't be inspected. It seems we likewise wouldn't have access to a nipple bonding device's connection. If we none-the-less must bond the nipple, where do we land the other end of the conductor, in the meter or through the nipple into the disconnect?
 
LarryFine said:
I looked at the above-mentioned code sections, and am left with a related question. Situation is a residential service with a main disconnect that has a threaded hub bolted to the top of it, and a close nipple that is lock-nutted to the bottom of the meter base through the largest KO, so there are no concentric rings left. The neutral conductor is bonded in both enclosures, so the nipple is merely the service raceway.

So, must a bonding locknut or bushing be installed on the top of the nipple? We're not allowed to land any GECs in meter bases since we're sealed out of them and they can't be inspected. It seems we likewise wouldn't have access to a nipple bonding device's connection. If we none-the-less must bond the nipple, where do we land the other end of the conductor, in the meter or through the nipple into the disconnect?
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I think this gets into the same question as with EGC's. In your specific case, I think you only need bonding on one end, because a fault to the nipple has a path that doesnt have to go through a standard locknut. Not take this situation: The same thing except the disconnect is a pull box and you dont tag that box with the neutral - you rely on the nipple to carry a fault on the box back to the meter can which is bonded to the neutral. In that case you would need service level bonding on both ends.

The way I think about is follow the fault path. It has to be able to get to the neutral conductor without traveling through a standard locknut.
 
LarryFine said:
I looked at the above-mentioned code sections, and am left with a related question. Situation is a residential service with a main disconnect that has a threaded hub bolted to the top of it, and a close nipple that is lock-nutted to the bottom of the meter base through the largest KO, so there are no concentric rings left. The neutral conductor is bonded in both enclosures, so the nipple is merely the service raceway.

So, must a bonding locknut or bushing be installed on the top of the nipple? We're not allowed to land any GECs in meter bases since we're sealed out of them and they can't be inspected. It seems we likewise wouldn't have access to a nipple bonding device's connection. If we none-the-less must bond the nipple, where do we land the other end of the conductor, in the meter or through the nipple into the disconnect?
Click to expand...

You need to bond a service raceway at one end with something other than standard locknuts. It could be a bonding locknut if you have a full size KO, a bonding bushing or a bonding wedge. Since there are no concentric or eccentric KO's I would use a bonding locknut on one end.
 
infinity said:
You need to bond a service raceway at one end with something other than standard locknuts. It could be a bonding locknut if you have a full size KO, a bonding bushing or a bonding wedge. Since there are no concentric or eccentric KO's I would use a bonding locknut on one end.
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So the threaded hub bolted to the top of the disconnect does not qualify?
 
LarryFine said:
So the threaded hub bolted to the top of the disconnect does not qualify?
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bolted on hub is not a locknut - it doesn't need additional methods to assure bonding - the rule basically is that service raceways can't rely on a standard locknut for bonding.
 
Well, the service installation passed inspection today, as the inspector obviously agreed with us. :happyyes:

He did ask me to move the water GEC from the grounding bus to the neutral bus, even though the neutral bus was bonded to the enclosure.
 
LarryFine said:
Well, the service installation passed inspection today, as the inspector obviously agreed with us. :happyyes:

He did ask me to move the water GEC from the grounding bus to the neutral bus, even though the neutral bus was bonded to the enclosure.
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He was correct if the MBJ is a screw. If it is a busbar then the GEC can land on either bus.
 
infinity said:
He was correct if the MBJ is a screw. If it is a busbar then the GEC can land on either bus.
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This disconnect has a typical multi-screw (about 6 screws) bus as the connector between the two neutral lugs, and two of those little copper do-hickeys that have one end flattened and attached to the enclosure with standard green grounding screws, and the other end is round and they're turned and inserted into two of the bus terminals.

The outgoing EGC (SER cable) is landed on a separate typical accessory bus that is bolted directly to the enclosure. The inspector had no problem with me leaving the driven-rod GEC on that bus. I used leftover conductors from the 4-0 aluminum SER to run between the meter terminals and the disconnect incoming terminals.
 
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