Fact Sheet: Oversized Circuit Breaker

To ensure electrical safety and proper functionality, it is essential to match the ampacity of the incoming mains cable with the rating of the circuit breaker. 

If the incoming mains cable has a lower ampacity (current-carrying capacity) than the circuit breaker, it can lead to the following consequences:

Overloading the cable: The circuit breaker is designed to protect the electrical wiring from carrying more current than it can handle safely. If the incoming cable has a lower ampacity than the circuit breaker, the cable may be subjected to excessive current, which can cause it to overheat and potentially lead to a fire hazard.

Tripping the circuit breaker: If the circuit breaker detects that the current flowing through it exceeds its rated capacity, it will trip or shut off the electrical circuit to prevent overheating and potential damage. In this case, the circuit breaker may frequently trip because the cable's lower ampacity cannot handle the current demands of the connected devices or appliances.

Voltage drop: When the current passing through a conductor encounters resistance, it results in a voltage drop. If the incoming cable has a lower ampacity than the circuit breaker, the cable's higher resistance can cause a significant voltage drop. This voltage drop may lead to reduced voltage levels at the connected devices, affecting their performance and potentially causing damage.

Electrical hazards: Inadequate current-carrying capacity can lead to various electrical hazards, including overheating, insulation breakdown, and electrical fires. The mismatch between the cable and the circuit breaker's ampacity ratings increases the risk of these hazards.


Was this article helpful?