ActronAir Crankcase Heater 50W (Metal) maintains compressor oil temperature during off-cycle periods on mid-capacity Classic Series and ESP Plus residential split ducted systems, preventing refrigerant from migrating into the compressor sump and diluting the oil -- which causes bearing damage and premature compressor failure on the first start after a cold soak. The 50W crankcase heater bridges the gap between the 30W residential and 75W commercial variants for systems in moderate-ambient conditions. Isolate power at mains before replacing any crankcase heater components.