Bonding Jumper
A bonding jumper is a reliable conductor used to ensure electrical continuity between metal parts that must be electrically connected, providing a low-impedance path for fault current so protective devices can clear faults. It ties separate metallic parts together to maintain the same electrical potential, preventing shock hazards.
On a shop floor, bonding jumpers are applied across metal raceway fittings, conduit sections, flexible connections to machines, and at service or transformer equipment. In Canadian practice, they connect non-current-carrying metal parts to the service equipment or system grounding conductor, emphasizing single-point grounding at the consumer's service. In NEC-based U.S. practice, bonding jumpers include equipment, main, system, or supply-side types depending on location. They ensure continuity across metal conduits and raceways, between machine frames and enclosures, at the service disconnect as the main bonding connection, and at separately derived systems like transformer secondaries.
- Wrong bonding point or multiple neutral-to-ground connections: In Canadian single-point grounding, the grounded conductor connects to the equipment bonding terminal at one point only; extra bonds create objectionable current on metal parts.
- Undersized, damaged, or discontinuous jumper: The jumper must be a reliable conductor sized appropriately; loose lugs, corrosion, paint, vibration, or broken strands can defeat continuity and prevent fault clearing.
- Confusing bonding with grounding: Bonding ensures electrical continuity of metal parts and fault-current paths, while grounding involves the grounding electrode system; mixing functions incorrectly is a frequent installation error.
What does a bonding jumper actually accomplish electrically?
It creates an effective low-impedance fault-current path between metallic parts so overcurrent devices operate quickly when an unintended phase-to-metal fault occurs.
Is a bonding jumper the same as a grounding conductor?
No. A bonding jumper connects metallic parts for continuity; a grounding conductor or grounding electrode conductor serves a different system-earthing function.
Where is the main bonding jumper used?
At the service, where it connects the grounded circuit conductor to the equipment grounding conductor and/or service enclosure.