ICC Residential Electrical Inspectors Practice Exam

A single motor supplied by a branch circuit shall have the branch circuit conductors sized not less than ____________ of the motor full load current rating.

1. 100%

2. 110%

3. 125%

4. 150%

The correct answer is: 125%

The requirement for sizing branch circuit conductors for a single motor is established to ensure that the conductors can handle the motor's full load current rating safely. The code specifies that the branch circuit conductors shall be sized not less than 125% of the motor full load current rating. This sizing takes into account the inrush current that occurs when the motor starts, which can be significantly higher than the full load current. By using 125% of the full load current, the conductors are adequately protected from overheating and potential damage, ensuring safe operation and longevity of both the motor and the electrical system. Choosing 100% or 110% would not provide sufficient capacity to accommodate the full load conditions the motor might experience under startup or overload situations. Selecting 150% would unnecessarily increase the conductor size and cost without providing additional safety benefits over the specified 125%. Thus, 125% is the optimal choice as it balances safety and efficiency in the sizing of branch circuit conductors for motors.