One neutral per terminal in panels
In a panelboard, each grounded (neutral) conductor must land on its own terminal. Two neutrals under one screw is a common inspection correction, because disconnecting one can disconnect the other.
What the code requires
Each grounded conductor, usually called the neutral, must terminate in its own individual terminal in a panelboard. That way, removing one circuit's neutral cannot disconnect another circuit's neutral.
A neighboring rule, 408.40, keeps equipment grounding conductors off the terminal bar for grounded (neutral) conductors, unless the bar is identified for that purpose and is located where Article 250 permits or requires neutrals and equipment grounds to be connected, such as at service equipment or a separately derived system. A main bonding jumper is required where the panel is used as service equipment (408.3(C)).
On the job
- Two neutrals under one screw is a common correction. Pulling one can disconnect the other, and on a multiwire branch circuit a lost neutral can cause over- and under-voltage on connected equipment.
- In a subpanel, neutrals and equipment grounding conductors mixed on one bar is a common correction.
Exceptions that matter
- Parallel neutral conductors may share one terminal if the terminal is identified for more than one conductor (110.14(A)).
Related sections
- NEC 408.40
- NEC 110.14(A)
- NEC 250.24: Grounding and bonding at the service
- NEC 250.142
- NEC 210.4: Multiwire branch circuits and shared neutrals
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