What does the symbol labeled "OL" represent as shown in the power circuit on lines T1 and T3 to the motor as shown in figure "A" of the illustration? EL-0011

Correct Answer: Option D — overload relay thermal heater

The OL symbol in the motor power lines represents the thermal heaters of the overload relay. These heaters monitor motor current and heat up proportionally, tripping the control contacts to protect the motor from sustained overcurrent, in compliance with 46 CFR 111.70 motor protection requirements.