Square D B4.15AK Overload Relay Thermal Heater Unit

The Square D B4.15AK Overload Relay Thermal Heater Unit is a thermal overload protection device for motor control circuits. It protects motors and motor starters by sensing heat generated by current and tripping the circuit when an overload condition is detected. As part of Square D's overload relay family, the B4.15AK is designed for use in industrial control panels to safeguard equipment such as pumps, fans, conveyors, and other electrically driven loads that rely on motor protection. Designed for integration with standard Square D motor starters, it provides a compact, reliable protection solution within typical panel layouts. In industrial settings, this thermal heater unit helps prevent winding damage and equipment downtime by providing fast automatic response to overheating conditions. Typical installation involves mounting adjacent to a compatible contactor and wiring per applicable electrical codes, with maintenance focused on ensuring secure connections and proper insulation in the control panel.