If a motor's full-load current is known, what percentage can be used to determine the maximum branch circuit size?

To determine the maximum branch circuit size for a motor based on its full-load current, the full-load current is typically multiplied by a factor of 125%. This percentage accounts for the additional capacity needed to prevent overheating and ensure reliable operation of the motor under varying load conditions.

Using 125% allows for a safety margin that compensates for potential starting currents, inrush currents, and other factors that may cause the motor's current draw to exceed its full-load current momentarily. This is important for circuit design, as it helps to prevent nuisance tripping of circuit breakers and ensures the motor can operate effectively without risking damage or failure.

The other percentages presented in the choices would not provide the necessary safety margin for maximum branch circuit sizing:

• A factor of 100% would only accommodate the full-load current, leaving no allowance for those additional current demands.

• An 80% factor is often used for continuous loads, indicating a focus on sustained use rather than accounting for the peak demands of a motor starting up or varying under load.

• A 150% factor, while perhaps seeming generous, would unnecessarily increase the size of the branch circuit, leading to inefficient use of materials and space without justifiable need for such a large capacity.

Thus, using a