Bonding is the use of conductors and other types of electrical components to establish electrical continuity between various metal components that enclose electrical conductors or equipment that may accidentally become energized.
Components that are commonly bonded are:
- Electrical service masts;
- Electric meter housings;
- Load center cabinets;
- Metal conduit;
- Water supply pipes; and
- Gas pipes(may vary by jurisdiction)
Bonding INSIDE the service panel
- Main bonding jumper. Grounding and neutral bus bars should be bonded together (only service panels, not in sub-panels);
Common methods that directly tie the bus bars are:
- Tie bar;
- Bonding jumper (if conductor, no smaller than gec)
Common methods that bond the bus bars by connecting them to the back wall of the cabinet are:
- Bonding straps;
- Bonding screws (green); or
- Mounting bus bars directly to the back wall of the cabinet.
Acceptable Bonding Connectors
- Conductors (adequate size);
- Threaded couplings and hubs;
- Threadless (compression) connectors;
- Bonding locknuts, bushings and wedges. (will have screw);
- Standard locknuts
Bonding OUTSIDE the service panel.
Any metal components that contain current-carrying conductors should be bonded both to each other, and to the grounded (neutral) service conductor. Some jurisdictions may not allow bonding of gas pipes.
Components commonly bonded are:
- Electrical mast;
- Meter housing;
- Metal conduit; and
- Any metal raceways grounded (neutral) service conductor.
Components that may accidentally become energized should be bonded to the rest of the electrical system:
- Metal water and gas pipes. Look for bonding at water heaters, and at points where pipes pass near the service panel or a sub-panel.
NOTE: In sub-panels, neutral bus bars must float, i.e., must not be bonded to the cabinet or grounding bus bar. Check to see that green-colored bonding screws have been removed or that other methods have been used to ensure electrical isolation of the neutral conductor.
Bonding in Sub-Panels
- Floating neutral bus bar. Neutral bus bar must not be bonded to the cabinet or grounding bus bar.
- No fused neutrals.