"Ground" is one of the most misunderstood words in electrical work. Here is what grounding and bonding actually do in a home.
What is the difference between grounding and bonding?
- Grounding connects the electrical system to the earth through ground rods, a concrete-encased "Ufer" electrode, or metal water pipe. It helps with lightning and utility surges.
- Bonding connects metal parts (boxes, appliance frames, piping) together and back to the panel, so if a hot wire touches metal, a large fault current flows and the breaker trips quickly.
The equipment ground wire (bare or green) in your circuits is about bonding: it gives fault current a path back so the breaker trips.
Why are neutral and ground separated in a subpanel?
Neutral and ground connect at one place, the main service disconnect. Downstream, in subpanels, they must be kept separate so normal current does not flow on ground wires and metal parts. See main panel vs subpanel.
Is my gas and water piping bonded?
Metal water piping and many gas piping systems are required to be bonded to the electrical system. Panel and service upgrades usually include bringing grounding and bonding up to current code.
Common questions
Do I need a ground rod?
Most homes have one or more grounding electrodes such as ground rods, a concrete-encased electrode or a metal water pipe. Service upgrades include bringing them up to code.
General information for California homes under the California Electrical Code (based on the NEC). Local rules and inspectors can vary. Not a substitute for an on-site inspection. Never work inside a panel, at the meter or on live circuits.