When installing a rigid conduit nipple between the back of a meter socket to the back of a panel is it required to have 2 locknut's on each end(in and out)and is only 1 bonding bushing required on either end of the nipple?
While I want to say that two locknuts are required on at each end of the nipple, I can't find a code rule that requires this. There are some rules in Chapter 5 that require double locknuts, but not in the general use chapters. Our power company requires grounding bushings at both ends, but the code rule in 250.92 does not really say that. This is one that I would run by the AHJ before making the installation. Don
I require bonding bushings on both sides of the nipple. With the neutral lugs of the meter fitting (pan) bonded to case ground, and the neutral bonded in the main panel, there is current flow on the nipple.
[This message has been edited by russ m (edited 04-04-2003).]
I like the way you got at that. I agree. Locknuts inside and outside of an enclosure wall.
About the bonding of the nipple at both ends. . .The raceway isn't a conductor. I agree that, when the raceway is conductive, it will be a parallel path for the unbalance current that is not returning towards the transformer through the GEC. But the neutral is chosen and sized for its current carrying properties, not the raceway except, if it is conductive, that it provide a fault current path of sufficiently low impedance as to clear the poco's OCP at the xformer.
While bonding the nipple at both ends provides even better performance, bonding it only at one end is all that is required on the poco side of the service disco & OCP.
Our poco doesn't make specific bonding requirements, rather, it leaves that to the NEC and the AHJ.