You can not land neutrals on your auxiliary grounding busbar.

East Wenatchee Home Inspections

Often in panels, especially older panels you will have a crowded condition on the Ground/Neutral Busbar where you land all the grounds and neutrals. In some cases I will recommend (especially of double lugging of neutrals are present) that to ease the crowding of wires on ground/neutral bus  that an auxiliary grounding bar could be installed to land all of the grounding conductors.

Auxiliary Grounding Busbar

One thing that must not be done is now land any neutrals (grounded conductors) on the auxiliary grounding busbar.

Neutrals on Aux. Grounding Busbar

By landing the neutrals (grounded conductor) may create an improper current path back to the service grounded conductor (Neutral). So in essence the panelboard enclosure is now a neutral conductor.  Not a good scenario.

So for those who want to know. Here is the code reference for this example.

From the 2014 NEC (Bold and underline is mine)

200.2 General

Grounded conductors shall comply with 200.2(A) and (B).

(B) Continuity.

The continuity of a grounded conductor shall not depend on a connection to a metallic enclosure, raceway, or cable armor.

Informational Note: See 300.13(B) for the continuity of grounded conductors used in multiwire branch circuits.

From the 2014 NEC Handbook-

“This section requires grounded conductors be connected to a terminal or busbar that is specifically intended and identified for connection of grounded or neutral conductors. Because grounded conductors are current carrying, connecting them to a separate equipment grounding terminal or bar (that is directly connected to a metal or enclosure) results in the enclosure becoming a neutral conductor between the equipment grounding terminal and the point of connection for the grounded conductor.”

Luckily this is a fairly easy correction but simple mistakes can get someone hurt.

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