A capacitor is an electric component that temporarily stores an electrical charge. A dual "run capacitor" supports two electric motors, such as in large air conditioner or heat pump units, with both a fan motor and a compressor motor. It saves space by combining two physical capacitors into one case. The dual capacitor has three terminals labeled "C", "FAN", and "HERM", which stand for the *C*ommon, Fan, and *HERM*etically sealed compressor. Dual capacitors come in a variety of sizes, depending on the capacitance (µF or MFD), such as 40 plus 5 µF, and also the voltage. A 440 volt capacitor can be used in place of a 370 volt, as it is build better, but the 370 can't be used in place of a 440 volt. It will work for a while and will fail prematurely, as exceeding the capacitor's rated voltage will cause the dielectric to break down and the capacitor to short out. Same as an electric wire- 600V rated wire is better than 300V one .The capacitance(µF or MFD) must be the same or stay within +10% or -10% of its original value . Example: 50 µF cap can be substituted by 45 to 55 µF with the same or better voltage ratings capacitor . Round cylinder-shaped dual run capacitors are commonly used for air conditioning, to help in the starting of the compressor and the condenser fan motor.Round capacitor can be used to substitute oval shape one with the same MFD AND Volt specs You will ask “Why I need a Cap that is rated 440V in my A/C?” Answer: You need to realize that a motor is an inductive device. When the supply voltage is applied to the motor run winding, the voltage across the start winding will be increased to a higher voltage value. A motor acts like a transformer with the run winding acting as the primary and the start winding acting as the secondary. This is why the capacitor has a much higher voltage rating than the 230 being the supply voltage.