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How can I tell a main electrical panel from a subpanel?
Tuesday, March 1, 2022
The main panel is the one that connects directly to electrical service coming into a home. Electricians refer to it correctly as the "service panel." It is the first in line after the meter, and has a main circuit breaker that shuts off all the electricity to a house. That breaker should be clearly marked as MAIN.
Older service panels were allowed to have up to six breakers that have to be shut off to disconnect all power, and each one is required to be marked MAIN. See our article What is a split bus electric panel? for details.
A subpanel receives electricity through the service panel. It can be disconnected by shutting off the MAIN breaker in the service panel, or a breaker that is marked as serving the subpanel. There may also be a breaker in the subpanel that disconnects its incoming power, but that's optional and not required.
It can be difficult in some instances to tell a subpanel from a service panel by only looking at it, especially if you haven’t located all the electrical panels in a house. But here is what you can tell without having to remove the dead front (cover plate) of the panels:
•• If there is a panel on the outside wall of the home next to or near the electrical meter, and another inside, then the outside panel is typically the service, and the inside one is a subpanel. There can be further subpanels behind a subpanel, such as a pool panel. The 2020 edition of the National Electrical Code now requires a service panel at the exterior of new homes. See What is the fireman’s switch emergency disconnect requirement for residential electrical service? for more on that.
•• The service panel for a mobile/manufactured home will be on a post, either near the home or next to an exterior wall. Also see What is the difference between the electric service to a mobile home and a site built home?
•• The service panel for most condominiums is in a small box with only a main breaker switch, next to the unit's meter in a cluster at ground level at the side of the building or in a meter room. Go to for photos Where do I find the the main electrical breaker/disconnect to shutoff power for a condominium? and details.
•• If it’s a larger home (over about 3,000 sq ft) and has two identical panels next to each other, they are both main panels.
•• Because sometimes the original service panel has been converted to a subpanel as part of a service upgrade, a large breaker marked MAIN does not automatically mean you have found the service panel.
There is also an easy way to be verify that you got it right—as long as you are positive you have located all the panels in the house. Shut off the main breaker at the panel you think is the main/service. If you have the correct panel, then any other panels around the house, along with all electrical appliances, receptacles, and fixtures, will be dead. You can confirm that a panel is dead with a tic-tracer held against the surface of a circuit breaker switch in the panel. See How does a home inspector use a tic-tracer (non-contact voltage tester)? for more on this.
Subpanels are required to be wired in a slightly different configuration than a service panel, with the neutral wires isolated on a separate bus from the bonded ground wires. To learn more, go to Why is it unsafe to bond neutral and ground wiring at subpanels?
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