Square D B22 Thermal Overload Relay Heater Element Unit

The Square D B22 Thermal Overload Relay Heater Element Unit provides reliable motor overload protection by converting motor current into heat that activates a time-delayed thermal trip in Square D thermal overload relay systems. Manufactured by Square D (Schneider Electric) and designed as a plug-in heater element for overload relay bases, it is compatible with Square D Type B and Type S frames. The unit supports a Full Load Current Range of 12.1–16.5 A, as listed in Grainger, and uses a melting alloy / bimetal thermal sensing element to trigger protection with a Class 20 trip. It serves industrial motor protection in conveyors, pumps, compressors, HVAC systems, and manufacturing equipment, and is commonly installed in motor control centers (MCCs), OEM panels, and industrial automation systems where accurate motor protection is required based on motor full-load current ratings. The device functions as part of motor overload protection via its time-delayed thermal trip mechanism, ensuring protection for motors under overload conditions. Common replacements include Square D B21 Thermal Heater Element, Schneider Electric LRD Series Thermal Units, and Siemens 3RU11 Thermal Overload Heater Elements.