What is a Bonding?

Understanding Bonding

Bonding is the planned connection of conductive parts in an electrical system. These parts can include metal enclosures, raceways, cable armor, and equipment grounding conductors. They can also include water piping and structural metal that may become energized. These connections keep the parts at nearly the same electrical potential.

Related glossary terms: Electrical Grounding, Grounding Electrode, Continuity Test.

Bonding doesn't normally carry operating current. Its main job appears during a fault. A fault can happen when a damaged conductor touches a metal panel. A sound fault-current path carries current back toward the source. This helps a circuit breaker or fuse open the circuit quickly. Grounding and bonding work together, but they perform different functions.

How Bonding Works, Is Measured, or Is Used?

A bonding connection uses approved conductors, terminals, jumpers, bonding screws, or listed fittings. The connection must remove paint, rust, dirt, or other coatings. This allows metal-to-metal contact when the design requires it.bonding jumper may connect two sections of metal raceway. It may bridge a flexible connection. It may also maintain continuity around equipment that could interrupt the path.

Electricians check bonding through inspection and testing. A continuity test checks for a low-resistance path between connected metal parts. A meter can help find an open connection or unexpected resistance. Test results need context because several factors affect the reading. These factors include lead resistance, parallel paths, equipment design, and the test instrument. The installer also checks conductor size, termination torque, listed fittings, and connection points. These checks must follow the applicable National Electrical Code requirements.

Why Bonding Matters?

Effective bonding reduces the chance that accessible metal stays energized after an insulation failure. It also gives protective devices a stronger path for fault current. This can reduce the time that a fault persists. Without that path, a breaker may not trip as intended. A person touching the equipment could then become part of the fault path.

Bonding also supports reliable operation of electrical equipment. It helps limit voltage differences between connected metal systems. Problems often develop after remodeling, panel replacement, water damage, corrosion, or unapproved wiring changes. A complete inspection looks beyond the panel. It checks raceways, boxes, service equipment, branch circuits, and other conductive parts.

When Bonding Matters Most?

Bonding deserves close attention during a service upgrade, panel change, generator installation, or major rewiring project. It matters when older wiring has been altered. It also matters when metal conduit has been cut. A replacement device might not preserve an existing connection. Service equipment also requires careful separation and connection of grounded and grounding conductors. These connections must follow the system design.

Warning signs include tingling from a metal appliance, repeated breaker trips, visible corrosion, loose wires, damaged raceway, and missing bonding screws. Electrical work without inspection records is another warning sign. Don't rely on a water pipe, gas pipe, or random metal object. These items aren't substitutes for an approved bonding path. In Cincinnati, older homes and buildings may contain several generations of electrical work. Tracing each connection can reveal defects that a simple outlet test misses.