Schneider Electric B40 Thermal Overload Relay

Schneider Electric's Square D B40 Thermal Overload Relay heater element unit is a plug-in heater element for Square D Type B and Type S overload relay frames that provides motor overload protection by converting motor current into heat to actuate a melting alloy/bimetal trip mechanism. The unit supports a full-load current range of 21.8–29.0 A (typical calibration varies with relay frame), and it is configured for Class 20 thermal protection. It is used inside Square D motor starters and overload relay assemblies in industrial motor control systems such as conveyors, pumps, compressors, HVAC systems, and heavy machinery, and is commonly installed in MCCs, OEM control panels, and industrial automation setups.