For a circuit that requires 60 amps using a 240-volt supply, what rule is applied for sizing the circuit breaker?

The reason for sizing the circuit breaker using the load multiplied by 1.25 is based on the National Electrical Code (NEC) guidelines, which provide safety margins to account for potential overloads. In this scenario, with a circuit requiring 60 amps at a 240-volt supply, the recommended approach is to size the breaker at a higher rating than the actual load to ensure it can handle temporary overload conditions without tripping unnecessarily.

By applying the 1.25 multiplier to the actual load of 60 amps, one calculates the required breaker size as follows:

1.25 x 60 amps = 75 amps.

This means the circuit breaker should be rated for at least 75 amps to accommodate any fluctuations or surges in the current without risking tripping the breaker, which could compromise the circuit's performance and safety. This rule allows for more reliable operation while still protecting the circuit from faults or short circuits.

Using only the actual load, adding a percentage such as 10%, or considering only minimum load results in insufficient protection against overloads, which could lead to circuit failure or hazards. Therefore, the safest and most compliant method requires using the load multiplied by 1.25 for breaker sizing.