and V12 models

Built for non-reversing operation

brass flare fitting designed for high-pressure refrigeration and HVACR service

Automatic Reset: Eliminates nuisance manual resets by restoring the circuit once temperatures drop below the 140°F cutout threshold

Lennox 15D57 Defrost Board R-410A and V12 modelsThe Lennox 15D57 Defrost Board is a high performance OEM defrost control kit specifically engineered for direct replacement in Lennox heat pump systems. As a veteran grade HVAC replacement part, this kit integrates a demand defrost control logic that actively monitors outdoor coil temperatures via the included 28W71 ambient sensor harness. This prevents excessive frost accumulation and optimizes system efficiency during low ambient operation. The