These units can increase starting torque from 300% to over 600% depending on the model used. They can be used on room A/C, all residential and commercial PSC A/C units and heat pumps. They can be used on units rated from 4,000 to 120,000 BTU’s and they can be used on 120 through 288 VAC units. All models are UL recognized and are for low voltage and hard starting compressors. All units contain a start capacitor and relay for extra starting torque. Installs in seconds across run capacitor terminals.