Circuit Breaker Types

Standard circuit breakers monitor the flow of electricity as it enters your home and makes its way through your electrical wiring system to outlets, light fixtures, appliances and electronics. As long as the electrical current operates within levels determined by the breaker’s ratings, the flow of electricity continues unhindered. However, in the event of an overload or short circuit — caused when a hot wire touches a neutral wire, ground wire or another hot wire — the breaker trips and breaks the current to prevent wires from overheating and diminish the potential for electrical fires.

Single-pole breakers protect one energized wire and supply 120V to a circuit.

- Standard single-pole breakers are generally 15 or 20 amps.

- Single-pole units, which occupy one slot on a breaker panel, are the most common breakers in a home.

- Three types of single-pole breakers are available:

    · Full size, which is 1 in. wide;
    · Half size, which is 1/2 in. wide; and
    · Twin or tandem, which is 1 in. wide, has two switches and controls two circuits.
Double-pole breakers typically occupy two slots on a breaker panel and consist of two single-pole breakers with one handle and a shared trip mechanism. They

- Supply 120V/240V or 240V to a circuit;

- Protect two energized wires;

- Range in capacity from 15 to 200 amps; and

- Are required for large appliances like dryers and water heaters.

Ground fault circuit interrupter (GFCI) circuit breakers cut power to the circuit when they are tripped by an overload of current, a short circuit or a line-to-ground fault, which occurs when an unwanted path forms between an electrical current and a grounded element. All GFCI breakers have test buttons on the front and coiled wires. They function in the same way as GFCI receptacles, but protect an entire circuit, eliminating the need for GFCI receptacles on that circuit. Both GFCI circuits and receptacles should be installed as recommended by the National Electrical Code (NEC). GFCIs are:

Required in kitchens, bathrooms, outdoor areas, basements and garages; and
Recommended for workshops and areas where power tools are in use.

GFCI protection is not recommended for appliances that must run all the time, such as refrigerators or medical devices, because the breaker may trip without your knowledge.

Arc-fault circuit interrupter (AFCI) breakers

AFCI breakers protect against an unintentional electrical discharge in an electrical cord or wiring that could cause a fire. Once the breaker senses the electrical jump and abnormal path, it instantly disconnects the damaged circuit before the arc builds enough heat to catch fire. Arcs generally occur due to worn or damaged electrical cords and wiring. Regular circuit breakers don’t always trip in these instances because standard breakers are designed to respond to a sustained amount of heat, not a quick surge. In new construction or renovation, the 2008 NEC requires an AFCI breaker for any 15 or 20 amp 120V circuit that includes a receptacle or light fixture, other than GFCI protected outlets in kitchens, bathrooms, unfinished basements and outdoors.

Arc faults occur most often in one of two situations:

In older homes where the insulation around the wiring becomes cracked or damaged, and
During new construction, when insulation surrounding wiring is pierced or nicked.

Arc-fault circuit-interrupter (AFCI) breakers look very much like GFCI breakers, right down to the test buttons and coiled wires. In fact, often the only way to tell them apart is to read the fine print on the breaker. Because the two function in different ways, be sure to read the fine print on the breaker to ensure you’re buying the correct breaker for the correct application.

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Considerations
Load capacity — When adding a new circuit and new circuit breaker, determine the amp size of the circuit breaker you need to install, based on the total circuit load. Keep in mind that the safety rating for circuit breakers is 80% of the maximum load. So you can only safely operate appliances rated at a total of 12 amps on a 15-amp breaker or 16 amps on a 20-amp breaker. Most appliances have the amp rating listed on them. Permanently installed large appliances, such as A/C units, washing machines and ovens, require their own dedicated circuit. Consult an electrician if you are unsure of your total circuit load.

Compatibility — Always install the correct brand of breakers in your breaker panel. While some breakers are interchangeable, many are not, even if they look the same. Replacing one brand of breaker with another can be dangerous, may void your breaker or panel warranty and may cause you to fail an electrical inspection. Look on your breaker panel door for information about which breakers are compatible with your panel. Breakers continue to be manufactured for most panels, including older models.

Refer to the table below for a list of panels and compatible circuit breakers. Do not rely solely on this table. To ensure compatibility, consult the manufacturer of your breaker panel when possible as well as an electrician before installing any circuit breakers.

Limitations

Circuit breakers are designed to protect home and building wiring, not appliances. They generally will not trip if a short or fire occurs in an appliance, or if an appliance or fixture overheats.
Standard breakers do not protect against surges, such as from lightning, which can damage electronics. To learn how to protect against surges, see our Surge Protector Buying Guide.

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Safety
Working within a breaker panel and installing new circuit breakers is very dangerous and best left to licensed electricians. Even minor electrical work may require a permit, so be sure to check local building codes before having any work done. In addition, keep the following things in mind when replacing or installing new circuit breakers:

Always shut off the main breaker before beginning any work in a breaker panel.
Be sure the device you choose matches the wiring, load requirements and type of breaker panel you have. The information should be on the breaker panel door.
Never replace a circuit breaker with one of a higher amperage rating.
Only add an additional breaker if you have an open slot in your breaker panel.
The bus bar in the electrical panel may still be hot even if the main power is off.
The wires leading into the electrical panel are always energized and should never be touched.
Always have new electrical work inspected to ensure that it's properly installed and meets code requirements.
Test AFCI and GFCI breakers every month to ensure they are in good working condition.