Easy Wiring of the iFLOW Heat Pump L1 & L2 @ 120VAC each legOnly 3 x 24V Control Wires to iFLOW Heat Pump ODU (Y, C, O/B) Wiring of the iFLOW Smart Hybrid Heating Controller Use any thermostat (do not need a heat pump thermostat);3 Wire Thermostat (iFLOW can operate even with only 3 wires in the wall (R, W, Y); no need to rewire;Only 3 Wires to iFLOW Heat Pump ODU (Y,C, O/B)