What you need to know about circuit breakers
The purpose of circuit breakers is to protect the circuit by "breaking" the electric flow (or the "circuit"). A circuit breaker will trigger (or "trip") when the heat or current in the circuit has reached a certain pre-set level. The difference between a circuit breaker and a fuse is that fuses need to be replaced when triggered, and circuit breakers can often be reset by a simply flipping a switch.
Circuit breakers are absolutely required to protect any electrical system. For example, in every home, you will find an electrical enclosure that contains an array of circuit breakers that protect various circuits throughout the property. You might find a circuit breaker for kitchen, a circuit breaker for the furnace system, a circuit breaker for the air conditioner...etc.
External shell of circuit breakers
Depending on the size of the circuit and the current rating, different types of casings are used. For low voltage circuit breakers (less than 1,000 V-AC rating), molded case exterior is often used. For medium voltage circuit breakers (between 1,000 to 72,000 V-AC rating), insulated case exterior is often used. And for medium to high voltage circuit breakers (more than 72,000 V-AC rating), metal clad exterior is the safest choice.
The external shell of a circuit breaker is very important to the safety of the circuit's surroundings. When circuit breakers are triggered, the internal electrical contacts are separated and disconnected from each other. When these contacts are disconnected, electricity have the tendency to jump from these contacts, resulting in an "electrical arc". Such arc can generate a lot of heat and may melt the exterior shell of the circuit breaker if the material is not strong enough to withstand the high temperature. For additional safety and protection, most circuit breakers also use an arc quenching mechanism to eliminate or reduce the electrical arcs.
How do circuit breakers trip?
Every circuit breaker uses a tripping element that is calibrated to activate when the current and/or voltage in the circuit reach a certain point. For example, if a circuit breaker is designed to trigger on 10A AMP (10A rating), if you operate a machinery that draws more than 10A AMP, the circuit breaker will activate and cut the power to the machinery.
There are also circuit breakers that will trigger on heat and temperature. These thermal circuit breakers will disconnect the circuit once it detects temperature beyond the pre-configured level. This types of circuit breakers are designed for protection against overheating.
What to look for when buying circuit breakers?
If you are replacing an existing circuit breaker that is broken, it is best to purchase a replacement with matching brand and model numbers. This will ensure compatibility of the component with the existing circuit.
If you are not able to find a replacement with matching brand and model numbers, you can find a compatible one by another manufacturer. It is very important to make sure the circuit breaker type is correct (thermal or voltage/current circuit breakers) and the rating matches.
If you are replacing a 10A AMP circuit breaker with a 7.5A AMP one, you may find it tripping more often than before.
Do not replace a circuit breaker that has higher rating than the existing one. If you replace a 10A AMP circuit breaker with a 20A AMP circuit breaker, the circuit breaker will not trip until the circuit has exceeded 20A AMP current of electricity. Your circuit breaker can handle anything between 10 and 20A AMP, but the circuit itself may not.
For example, the wires used in the circuit may not be able to handle 20A AMP of current and will overheat and potentially result in fire damages before the circuit breaker trips.
Installation safety tips
1. Before you remove the existing circuit breaker, make sure it's in the "tripped" position. This can be easily identified by comparing with the breaker switches nearby.
2. Make sure the breaker is actually in the tripped position. Try to power on a machinery connected to the circuit to see if there's power to it. If not, okay to proceed.
3. Make sure that all of the machines connected to the circuit is "powered off".
4. Turn off the master power.
5. When removing a circuit breaker, make sure that you are wearing shock resistant gloves.
6. When installing a circuit breaker, make sure that the new circuit breaker is in the "tripped" position.
7. After the new circuit breaker is installed, turn on the master power. Confirm that there's no power in the circuit.
8. Flip the switch on the new circuit breaker. Confirm that there's power in the circuit.