Thread: Bonding

should not the metal conduit between the utility meter and service equip. panel be bonded to the panel? Also, what on earth is there a conductor at the bottom of the breaker, labled B, not going to anything?

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Thanks, Robert.

Originally Posted by Robert Meier

It need to be bonded by a means other than standard locknuts one end or the other. The bonding could be in the meter enclosure.

That would not do much good ... unless it was also bonded at the panel enclosure too.

Originally Posted by Robert Meier

It need to be bonded by a means other than standard locknuts one end or the other. The bonding could be in the meter enclosure.

Good answer. It only needs to be bonded on one end and if it is bonded in the meter enclosure, it is good enough. Because it is sealed it makes it difficult to make a good assessment of the bonding.

Bonding addressed, I think your supposition that one of those service legs, ( wires ), is doing nothing is incorrect. Hard to know w/o being there, but those home made wire labels are covering where I think the missing connection is. If there is / was 240 volts inside, my speculation is correct.

Originally Posted by Roland Miller

Good answer. It only needs to be bonded on one end and if it is bonded in the meter enclosure, it is good enough. Because it is sealed it makes it difficult to make a good assessment of the bonding.

The problem with only bonding it on one end is that if a fault current is on that grounded conductor between the service equipment and the meter, then fault current is also on, or trying to get on, that metal nipple, and every time there is, is not, then is contact again between the metal nipple and/or its locknut at the unbonded end, there will be arcing, and if a person were to be working on that when such happened, *they* may become part of that fault current path - thus it needs to be bonded to ground at *each end*.

Bonding both ends of the nipple between the meter and the service panel puts the nipple and bonding jumper in parallel with the grounded conductor in violation of NEC 310 (H). And causes neutral current to flow under normal load conditions on the bonding jumpers and nipple.This would need to be corrected as stipulated in 250.6. So the bottom line is you should only bond one end of this nipple.. I have found this to be a very common error with electricians and others as well.

The explanation involves understanding fault current analysis and parallel resistances. Concentric/eccentric ring blow-out under fault conditions will not occur with one end bonded as long as the raceway and fittings themselves are assembled correctly.

I think making this kind of assessment as a Home Inspector is risky at best..
All 2011 NEC

Originally Posted by Roland Miller

Bonding both ends of the nipple between the meter and the service panel puts the nipple and bonding jumper in parallel with the grounded conductor in violation of NEC 310 (H). And causes neutral current to flow under normal load conditions on the bonding jumpers and nipple.

This would need to be corrected as stipulated in 250.6.

All 2011 NEC[/QUOTE]

Bonding one end and not bonding the other end *would not meet* the requirements of 250.6. The end *not bonded* would need to be intentionally isolated from ground to meet 250.6.

Not bonding both ends creates a problem, bonding both ends creates a different problem - there are many AHJ which *require* a separate ground be run from the meter to the service equipment, such as when the piping is PVC, and that separate ground creates the same problem with your parallel neutral paths.

To meet 250.6(B) one would be required, in this case, to meet (3) or (4), with (3) being accomplished by isolating the unbonded end, and (4) being accomplished by replacing that metal nipple with a PVC nipple - this action would also meet (1) and (2) of 250.6(B), which, by the way, says "one or more of the following alterations shall be permitted to be made.", so replacing that metal nipple with a length of PVC with a male adapter on each end meet the "one or more", bonding one end of the metal nipple *does not meet any of them*.