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An electrical circuit breaker panel is also commonly referred to as a distribution board, breaker panel, or panel board. A circuit breaker is a component of a supply system that divides electrical power into branch or secondary circuits.
In the United States, an electrical circuit breaker panel is normally housed in a sheet metal enclosure. The circuit breakers are aligned in two columns with switches numbered left-to-right, at each row from top to bottom. The position numbers are universal with various manufacturers in the U.S. In this article, we’ll discuss the ins and outs of how a standard electrical circuit breaker panel is designed and its function.
From your utility service lines, power is sent to the electrical meter at the exterior of your home or building, continues at your service panel. The main breaker is used to turn the power on or off to all branch circuits wired into your property.
Electrical Circuit Breaker Design
The sheet metal enclosure that houses a circuit breaker panel is vertical, placed at or near the electrical main to a home or commercial property. Each row of the breaker panel is fed from a dedicated two or three phase pole. In the U.S., it is common to wire larger permanently installed equipment from line-to-line. This takes two slots in the panel and gives a voltage of 240 V for two-phase power, or 208 V for three-phase. The standard voltage for an American home is 240 V. For commercial property, the standard is 208 V.
The panel housing has three service conductors – two positive lines connect to the main breaker and one neutral line connects to the busbar. The busbar functions as a junction between in-coming and out-going currents. Following U.S. National Electric Code standards, the main panel must have a grounding conductor, a necessary part of the electrical path to the circuit breaker.
Each circuit breaker services a dedicated line to different rooms and areas of the building. Each breaker can be flipped to the ON or OFF position. The main switch is connected to all panel breakers. It’s recommended to label each circuit breaker for the room or appliance it services. If a repair or upgrade is needed, labeling the breakers also helps your electrician identify if there’s an issue with either the circuitry or at a specific outlet point.
Typically, the main panel services the entire home, but may include a subpanel to service an in-law unit or detached garage.
The face of the panel is normally called the dead front cover. Opening the dead front gives a technician access to wiring and components inside the panel after turning off the power at the main circuit breaker. It is recommended to only have a licensed electrician deal with issues related to the main breaker.
For your reference, the two black wires at the main circuit breaker carry 120 V from your meter to the hot busbar. From here the power leaves the service panel and does its work at devices such as light bulbs and outlet points. The current then returns to the neutral circuit wire. The circuit breaker is the link to each electrical circuit in your home or building. If a circuit becomes too hot it could be a potential fire hazard. Therefore, circuit breakers are designed to fail safely with over-current safety devices, which essentially is what a breaker is (electrical panels manufactured before 1965 were made to house fuses).
Common Types of Circuit Breakers
There are various types of circuit breakers and capacities. Below is a checklist of what is commonly used:
- Single-pole/120 V with ratings at 15 – 20 amps. These are the types of breakers commonly used in an American home to service smaller appliances.
- Double-pole/240 V with ratings between 15 – 50 amps. These are commonly used for a dedicated circuit to a large appliance.
- Ground-fault circuit interrupter (GFCI) is used to protect a circuit and is required for homes or buildings near bathrooms or areas with unfinished concrete floors.
- There are also dual GFCI and arc-fault circuit interrupters (AFCI) available.
It is recommended to have your electrical circuit breaker panel inspected every three to five years. If you experience repeated circuit tripping, outlets not functioning properly, or lights flickering an inspection is also warranted.