Parts of a Breaker Box – Labeled Electrical Panel Diagram

All 11 parts on the diagram

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Door open 5

Door The door closes over the breaker handles. A list of the circuits is usually kept inside it.
Dead front cover The cover closes the front of the box. The live parts stay behind it. That is why it is called a dead front.
Main breaker The main breaker is the largest switch in the box. It switches the power to all the other breakers on or off at once.
Two-pole breaker It takes two slots in the box and has one wide handle. It feeds a large 240-volt circuit.
Branch circuit breakers Each branch circuit breaker guards one circuit in the building. It switches itself off when too much current flows.

Cover off 6

Enclosure The enclosure is a sheet-metal box fixed to the wall. It is also called the cabinet or simply the box.
Service conductors They bring the power into the box from outside. There are two hot lines, which end at the main breaker, and one neutral.
Bus bars They carry the current from the main breaker down the box. The branch breakers clip onto their tabs.
Neutral bar A metal strip with a row of screw terminals. The neutral wire of every circuit ends here.
Ground bar A strip of screw terminals fixed to the metal box. The ground wire of every circuit ends here.
Knockouts A knockout is a round disk cut part way through the metal. One is knocked out to make a hole where a cable enters the box.

How this list was compiled: Part names checked on 2026-09-30; a name is kept only when two independent sources use it. (1) Wikipedia, Distribution board, text only, https://en.wikipedia.org/wiki/Distribution_board (the sheet-metal enclosure; circuit breakers in two columns; the door over the breaker handles; dead front; bus bars that carry current from the incoming hot conductors to the breakers; the neutral bus and its screw terminals; the ground bar; the three service conductors, two hot and one neutral; the main breaker above the two bus bars; a two-pole breaker taking two slots for 240 V). (2) US Occupational Safety and Health Administration, 29 CFR 1910.399, Definitions, https://www.ecfr.gov/current/title-29/section-1910.399 (circuit breaker, which opens a circuit automatically on overcurrent; panelboard with its buses; cabinet and enclosure; dead front; service-entrance conductors; branch circuit). (3) A panel maker's catalog, Square D Digest 152, https://archive.org/details/squareddigest152 (load centers: main breaker, branch breakers, main bus bars, solid neutral bar, ground bar kit, door, cover, knockouts, two-pole breakers, dead front construction). (4) Two installation manuals by makers of other equipment that names the parts of the house load center: Generac, https://archive.org/details/manualzilla-id-7283077 (main breaker, branch circuit breakers, neutral bar, ground bar, knockout, dead front cover, 2-pole breaker) and GenTran, https://archive.org/details/manualsbase-id-439092 (main breaker, branch circuit breakers, neutral bar, ground bar, knockouts, 2-pole breaker). Makers and the agency are named here only; the page names none. Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; own work, no maker's panel copied. Licence: own work

How it works

These are the parts of a breaker box in a North American home, also called an electrical panel. The first view has the door open. The second shows what an electrician sees with the cover off. Names only.

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From the door inward

Behind the door is the dead front cover, with the main breaker at the top and the branch circuit breakers in two columns. A two-pole breaker fills two places. With the cover off, the service conductors come into the enclosure at the top. Two bus bars run down from the main breaker, and the breakers clip onto them. The neutral bar and the ground bar are strips of screw terminals. Knockouts are the round disks in the metal.

Breaker box, electrical panel, load center and panelboard are names for the same thing.

Questions and answers

What are the parts of an electrical panel called?

On the front: the door, the dead front cover, the main breaker and the branch circuit breakers. Behind the cover: the enclosure, the service conductors, two bus bars, the neutral bar and the ground bar.

What is the big switch at the top of a breaker box?

The main breaker. It is the largest switch in the box, and it switches the power to all the other breakers on or off at once.

What is a bus bar in a breaker box?

A long metal strip that carries the current from the main breaker down the box. A home panel has two, and the branch breakers clip onto them.

What is the difference between the neutral bar and the ground bar?

Both are metal strips with a row of screw terminals. The neutral wires of the circuits end at the neutral bar. The ground wires end at the ground bar, which is fixed to the metal box.