Bonding of grounded conductors to multiple points within a service panel

[Michael Thomas]

Is this diagram correct, i.e. bonding of ungrounded conductors to ground within the service equipment should only occur at at bus bars with a direct physical bond to the service neutral?

[Jerry Peck]

Is this diagram correct, i.e. bonding of ungrounded conductors to ground within the service equipment should only occur at at bus bars with a direct physical bond to the service neutral?


Michael,

???

Not sure of what you are saying there "bonding of ungrounded conductors to ground" ... ungrounded conductors are the 'hot' phase conductors and do not get bonded to ground.

If you are saying that the "neutrals" are only allowed to be bonded to the "neutral" terminal bar and not a "ground" terminal bar which is attached to the enclosure but not directly to the other neutral terminal bar, then yes, you are correct.

The reason is that if a neutral is attached to a ground terminal bar which is *only* attached to the enclosure, that the neutral current from that circuit is 'flowing through the enclosure' to the neutral terminal bar to which the neutral is directly attached.

Not sure if that is clear or if that is as clear as mud.

[Michael Thomas]

Sorry, complete brain fade there, should be "grounded (neutral) conductors", I've asked Brian to change the title to avoid confusing later readers.

That's how I understood it - that "objectionable current" is following the red path in the diagram, but just wanted to be sure.

[Jerry Peck]

There is an error on the drawing, at least regarding the "Suitable for use as Service Equipment Only" panels I've seen - there may be a new UL requirement stating this, in which case those "Service Equipment Only" panels would no longer be made - which could well be the case.

That drawing states: "To qualify as a neutral bar it must be set on insulated standoffs from the metal of the panel."

Being as some of the wording is unusual, i.e., "from the metal of the panel" instead of "from the metal enclosure" I suspect that is a "fairly accurate" but "not entirely accurate" drawing, in which case that statement I am questioning in that drawing may be incorrect.