Home Circuit Breakers Safety

Guide to Types of Circuit Breakers

A circuit breaker is an automatic electrical shutoff switch that protects circuits from overcurrent. Overcurrent, or excess amperage, can come from an overload of the circuit, short-circuiting, an arc fault or a ground fault. Circuit breakers make use of the increased heat or magnetic field from the current and use it to trip the circuit.

Circuit breakers have been in widespread use for nearly a century and are one of the most important fire safety tools in modern homes, buildings and appliances. Although they perform the same essential function as a fuse, they have the benefit of not needing to be replaced when overcurrent occurs, which saves money and allows for quick fixes

In this article, we will take a look at the different types of circuit breakers and what applications they’re best suited for. They vary according to what class of voltage they handle, how they’re constructed, what type of interruption they offer and what type of structural attributes they feature.

Low-Voltage Circuit Breakers

These are one of the most common types of circuit breaker on the market and can be found in homes, businesses and industries. They include the following models:

Miniature Circuit Breakers (MCB): Miniature Circuit Breakers do not handle currents higher than 100 amps, which makes them suitable for many home and business applications. Once installed, they’re simple to use but not very tunable — you can’t usually adjust their trip settings, for instance. They operate on thermal or thermal-magnetic properties.

Molded Case Circuit Breakers (MCCB): These circuit breakers can handle currents up to 2,500 amps, making them a more robust choice for higher-power residential and industrial purposes. With higher amp ratings, their trip load can typically be tuned.

What is the difference between MCB and MCCB circuit breakers? MCCBs can handle more voltage, and because of the different requirements set on them, they come in different casing and with different components. Low-voltage circuit breakers are designed to be easily serviced. They’re often easily disassembled for repairs without a user having to take the switchgear apart. Some assemblies are automatic, allowing an operator to open and close them remotely. These circuit breakers can also be used on direct current applications


As shown in Figure H20 the circuit-breaker/ disconnector is the only item of switchgear capable of simultaneously satisfying all the basic functions necessary in an electrical installation. Moreover, it can, by means of auxiliary units, provide a wide range of other functions, for example: indication (on-off – tripped on fault); undervoltage tripping; remote control… etc. These features make a circuit-breaker/ disconnector the basic unit of switchgear for any electrical installation.

Figure H21 shows schematically the main parts of a LV circuit-breaker and its four essential functions:

The circuit-breaking components, comprising the fixed and moving contacts and the arc-dividing chamber

The latching mechanism which becomes unlatched by the tripping device on detection of abnormal current conditions

This mechanism is also linked to the operation handle of the breaker.

A trip-mechanism actuating device:

Either: a thermal-magnetic device, in which a thermally-operated bi-metal strip detects an overload condition, while an electromagnetic striker pin operates at current levels reached in short-circuit conditions, or

An electronic relay operated from current transformers, one of which is installed on each phase

A space allocated to the several types of terminal currently used for the main power circuit conductors

Some models can be adapted to provide sensitive detection (30 mA) of earth-leakage current with CB tripping, by the addition of a modular block, while other models (RCBOs, complying with IEC 61009 and CBRs complying with IEC 60947-2 Annex B) have this residual current feature incorporated as shown in Figure H23.

Apart from the above-mentioned functions further features can be associated with the basic circuit-breaker by means of additional modules, as shown in Figure H24; notably remote control and indication (on-off-fault).

A Guide to Circuit Breakers and What They Do

What Are Circuit Breakers?

A circuit breaker is an automatically operated electrical switch designed to regulate the flow of electricity throughout your home or business. Just as the name implies, a circuit breaker is designed to cut or “break” the flow of electricity in the event of a fault or an overloaded current on a specific circuit. This is critical as it eliminates the risk of fires, burned wiring, and ruined appliances from an overloaded circuit.

Circuit breakers perform 3 key functions: protection, switching, and monitoring. Unlike a fuse, which operates and fails once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. A fuse is the simplest circuit protection device; it has a thin wire, enclosed in a casing, that plugs into and becomes part of the circuit. All the electrical charge and current flows through the fuse wire when the circuit is closed. If the current in this circuit climbs too high and becomes too hot, it burns the wire in the fuse, cutting the current. A circuit breaker does the exact same thing but doesn’t need replacing after it’s tripped.

A tripped breaker is easily fixed by simply pushing the switch back to the “On” position in the breaker panel. A circuit breaker panel contains the circuit breakers for each of the electrical circuits within a building. Before flipping the breaker back on, be sure to turn off light switches and unplug major appliances in the affected location. Continuing to overload the circuit will result in constant power outages.

How a Circuit Breaker Works

Circuit breakers consist of a simple switch, connected to either a bimetallic strip or an electromagnet, with a hot wire within the circuit connecting the two ends of the switch. With the switch flipped to the “On” position, electricity flows from the bottom terminal, through the electromagnet, up to a moving contact, and then across to a stationary contact and out to the upper terminal.

As it flows, electricity magnetizes the electromagnet and the increasing current boosts the electromagnet’s magnetic force. Conversely, decreasing current will lower the magnetism. If the current reaches unsafe levels, the electromagnet has enough strength to pull down a metal lever that’s connected to the switch linkage. This causes the entire linkage to shift, which tilts the moving contact away from the stationary contact, breaking the circuit. With this break, the electricity shuts off, preventing an overloaded circuit and potential damage.

An Easy Guide to Understanding Your Breaker Panel

Still scared of that big gray and black box in your utility room? It’s time to face your fear. Why should you get to know this mystery box? It receives and distributes electricity through your home, and without a little breaker panel know-how, you could end up in a dark or dangerous situation. Luckily, it’s not as complicated to understand and operate as you might think.

How’s It Work?

Your breaker panel is just a big switch, filled with other smaller switches. Like your living room light, flip them one way and you’ve got power, flip them the other and its lights out. As an added bonus, these switches, called breakers, perform an array of safety services, protecting your wiring from overload and your home and its inhabitants from fire and shock.

What Am I Looking At?

The ‘Big’ One – The Main Breaker

This switch is serves as the on/off for electricity in your entire home. 200-amps is typical for homes around 2,000 square feet, with smaller homes utilizing 150 or 100-amp varieties. In the case of an emergency, you can turn off power to your entire home by flipping this switch.

Two ‘Thingies’ – Double-Pole Breaker

Double-pole breakers come in different amperages, which are typically noted on the switch. Common household electronics use 15 and 20-amp, while larger appliances require higher amperage breakers: 30-amps for water heaters and clothes dryers; 40-50-amp for stoves; 70-amp breakers for an HVAC unit, etc.

One ‘Thingy’ – Single-Pole Breaker

These all-purpose breakers are capable of running lots of stuff in your home, from lights to garage door openers. 

AFCI-What? – Arc Fault Circuit Interrupters

These handy little breakers prevent fires in the case of accidental electrical discharge/arcing that normally won’t pull enough power to trip a regular breaker.

Huh? Empty Slots

These allow for additional circuits for today’s homeowners to add increasingly more ‘stuff’.

Why Do I Have 2? – Sub Panels

Sub panels (smaller breaker boxes) are often used with additions. Again, it’s a good idea to know what these panels run in case of emergency.

What On Earth Do These Breakers All Operate?

It’s a good idea for you to find out. Fumbling in dark is never good. Flip your switches on and off as needed to identify the zones/appliances in your home they serve – labeling your breaker box by room and area so you won’t have to play guessing games in an emergency.

What Do I Do If I Need to Reset One?

If a breaker trips in your home due to electrical overload, it’s usually easily identified, resting in a different position than others in the box (halfway between ‘off’ and ‘on’). To reset and restore power to the circuit, move the breaker to the fully ‘off’ position, then flip it back to the fully ‘on’ position.

A Quick Guide to Circuit Breakers

In the world of electronics, there are multiple cases and situations where unforeseen mishaps can take place. These disasters can lead to drastic damage and destruction of physical structures such as offices, homes, schools, industries, etc. A prominent case of such an accident is during a short-circuit or any other type of electrical blunder (electric cable faults), when high-fault current flows through the equipment as well as the power network grid itself.

This high current potentially damages the equipment connected in the system and the networks permanently. In order to safeguard these devices from damage, these fault currents must be removed from the grid as fast as possible. Even once it is removed, the system must be restored to its normal working conditions quickly in order to supply a reliable quality of power

In order to ensure timely disconnection and reconnection of various parts of a power system network for protection and control, there must be a unique type of device that can ensure operational safety and control under immense current-carrying conditions. This device is known as a circuit breakers: a special tool which performs the function of switching operations during current-carrying conditions.

Air Circuit Breaker

This type of circuit breaker, which functions in the air at atmospheric pressure, is known as an Air Circuit Breaker. These breakers have completely replaced oil circuit breakers. Their process of arc quenching control is completely different from that of oil circuit-breakers. They are normally used for a low-voltage interruption.

Miniature Circuit Breaker

An MCB is one of the most common devices used to safeguard electrical appliances from potential damages. Using an MCB is electrically reliable, especially when compared to a fuse. A swift restoration of electrical supply is possible as the switch has to be switched on, parallel to a fuse – a one-time device that subsequently needs replacement after accomplishing its purpose.