SL2640-MO is suitable for normal temperature or low temperature air source heat pump or hot water module unit. this controller can control 1 to 4 compressor systems, with 1 auxiliary electric heating, 1 chassis heating, 4 low temperature increase enthalpy, 1 crankshaft heating control, and supports main and auxiliary circuit electronic expansion valve control. the controller can expand up to 16 modules, and has the functions of built-in phase sequence protection, remote monitoring, antifreeze, intelligent defrosting and module equalization. 

NO is the relay normally open contact, NC is the relay normally closed contact, and COM is the common terminal.