What is a Bonding?

Understanding Bonding

Bonding is the deliberate connection of conductive parts that could carry electricity during a fault. These parts may include metal enclosures, raceways, and service equipment. They may also include grounding conductors and certain metal piping systems. The connections keep these parts near the same voltage. This helps limit shock risk when insulation fails.

Related glossary terms: Grounding Electrode, Equipment Grounding Conductor, Fault Current.

A bonding connection isn't intended to carry normal operating current. Instead, it creates a dependable fault-current path back to the electrical source. That path lets a circuit breaker or fuse open the circuit. This happens when a hot conductor touches metal. Bonding supports grounding, but the two have different roles. Grounding connects an electrical system or equipment to earth. Bonding joins conductive parts together.

How Bonding Works, Is Measured, or Is Used?

During a fault, current should travel through a low-impedance path. It shouldn't travel through a person. A typical path may run from a damaged energized conductor to a metal enclosure. It then passes through.equipment grounding conductor and back to the source. The current must be high enough to operate the protective device. It must operate within the time required by applicable electrical rules.

Electricians evaluate bonding by checking continuity, connection quality, conductor size, and termination strength. A meter can detect resistance or continuity. A simple continuity reading doesn't prove that a path can carry available fault current. Inspection also covers listed bonding hardware, tight terminals, and clean contact surfaces. It checks proper connections between metal sections.

At service equipment, the grounded conductor and bonding connection follow specific code rules. Downstream panels normally keep neutral current separate from equipment grounding paths. Connecting those paths in the wrong location can place normal current on metal parts. This creates an unsafe condition. It may also cause nuisance operation of protective devices.

Why Bonding Matters?

Effective bonding reduces the chance that an accessible metal surface stays energized after wiring fails. It also helps protective devices clear faults. This prevents heat, arcing, or sustained touch voltage from continuing. The safety benefit depends on the entire path. It doesn't depend on one wire or screw.

Bonding also supports dependable operation of ground-fault circuit interrupters and other protective equipment. A damaged, corroded, or disconnected bond can delay fault clearing. It can also leave equipment without a reliable return path. In older installations, later renovations may interrupt metal paths. They may also create improper neutral-to-ground connections.

When Bonding Matters Most?

Bonding deserves close attention during panel replacements, service upgrades, rewiring, and repairs. This includes repairs involving metal raceways or enclosures. It also matters after flooding, corrosion, lightning damage, or construction changes. These events can loosen terminals or damage conductors. They can also leave contaminants between bonding surfaces.

Common warning signs include tingling from metal equipment, repeated breaker trips, and visible corrosion. Other signs include missing bonding jumpers and metal parts with different test voltages. A licensed electrician can trace the fault path and verify conductor sizing. The electrician can compare the installation with the applicable edition.National Electrical Code and local requirements. Don't remove a bonding connection to stop a nuisance trip. That action can hide a dangerous fault.