Question 1

When should you make a neutral-to-ground bond in an electrical panel?

Accepted Answer

Make a neutral-to-ground bond only at the main service disconnect, the first point of disconnect from the utility.  Do NOT bond neutral to ground at subpanels.  If the panel is a subpanel (fed from another panel), keep neutral and ground separate.  If the panel is the main service disconnect and the utility provides only phase and neutral conductors (no separate ground), you must make the bond per NEC 250.24(B).

Question 2

What is the NEC rule for neutral-to-ground bonding?

Accepted Answer

NEC 250.24(B) requires the neutral conductor to be bonded to the grounding electrode conductor at the service.  NEC 250.142(B) prohibits using the grounded (neutral) conductor for grounding equipment on the load side of the service disconnect.  NEC 250.32(B)(1) prohibits neutral-to-ground bonds at separate buildings or structures fed from another building.

Question 3

What is the Canadian Electrical Code rule for neutral-to-ground bonding?

Accepted Answer

The Canadian Electrical Code (CEC) Rule 10-200(1) prohibits objectionable currents from flowing through the grounding system during normal operations.  Rule 10-204(1) states that neutral currents must not flow on the grounding system back to the transformer.  Rule 10-204(1)(c) prohibits making connections at the consumer service that would cause neutral currents to flow on the grounding system.  This mirrors the NEC prohibition on subpanel neutral-to-ground bonds.

When to bond neutral and ground? Should you make neutral-to-ground bonds in electrical panels?