Bonding of ALL raceways, enclosures etc.
Bonding of ALL raceways, enclosures etc.
Electron Sam78 asks:
250.97 talks about bonding metal raceway for 250+ volts but what about bonding raceway for voltages under 250 V?
Bonding for ALL metal raceways, cable trays, cable armor, cable sheath, enclosures, frames, fittings, and other metal non-current-carrying parts, that are to serve as grounding conductors, with or without the use of supplementary equipment grounding conductors, is governed under Section 250.96(A). Section 250.97 has heightened requirements where said bonding is for over 250-volts.
Please note that Section 250.96(A) provides specific performance requirements which must be met to accomplish said bonding, which includes "ensuring electrical continuity and the capacity to conduct safely any fault current likely to be imposed". Knockouts, including both concentric and eccentric, other those recognized in the 2009 UL White book Section QCIT, have never been recognized for such bonding. Meaning additional bonding, to meet the performance requirements, may be necessary for such knockouts. Section 250.96(A) goes on to inform that: "Any nonconductive paint, enamel, or similar coating shall be removed at threads, contact points, and contact surfaces or be connected by means of fittings designed so as to make such removal unnecessary." Be aware that no such fittings have ever been listed to make such removal unnecessary. Meaning: Enamel is NOT your friend?
I do hope this is helpful,
Mweaver