Subpanel bonding (3-phase mains) question

Is it never allowed (US National Electrical Code) to bond the ground bus bar
to the neutral bus bar?
I opened a subpanel and found that both the ground bus bar and cabinet were
bonded to the neutral bus bar.
Is this allowed under any circumstance?
This is a "Y" 208/120 configuration utilizing 5 conductors in an industrial
building.
Thanks.
Reply to
Mike Cook
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Is it never allowed (US National Electrical Code) to bond the ground bus bar to the neutral bus bar?
I opened a subpanel and found that both the ground bus bar and cabinet were bonded to the neutral bus bar.
Is this allowed under any circumstance?
This is a "Y" 208/120 configuration utilizing 5 conductors in an industrial building.
Thanks.
Reply to
notme
No, according to the NEC it is not allowed in a subpanel at all.
Reply to
Rich.
No. As long as it is a sub-panel. Not to be confused with a seperately-derived system(after a transformer).
RE
Reply to
Ryan Evans
With the exception of feeders to separate buildings under previous editions of the US NEC it is not permissible. -- Tom Horne
Reply to
Tom Horne
Single building, not large (2000 sq ft?) one service entrance, one main panel, 3 or 4 subpanels.
It looks like this bond needs to be broken...
Thanks, Mike (OP)
Reply to
Mike Cook
When you say 'sub-panel', it may be confusing. A step-down transformer fed from the service entrance, that in turn feeds 208/120 to a panel is not a sub-panel. In that case the first panel off the transformer is not a usual 'sub-panel' but a fed from a separately derived source (the transformer).
You mentioned 208/120 in an 'industrial building', so I think the building service is not 208/120 directly but may be a higher voltage and you have a step-down transformer inside the building.
In that case, the ground/neutral *should* be bonded in the first panel after the transformer.
Now, any other panels fed from the first panel after the step-down transformer are true 'sub-panels' and thus should not have the ground and neutral bonded.
So just to be clear here, are you talking about a true 'sub-panel', or the first panel downstream of a step-down transformer?
daestrom
Reply to
daestrom

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