jbcapacitors blog

A dual run capacitor supports 2 electric motors, such as in large air conditioner or heat pump units, with both a fan motor and a compressor motor. The dual capacitor has 3 terminals labeled "C", "FAN", and "HERM" for the common, fan, and hermetic compressor connections.

Round dual run capacitors (shaped as round cylinders) are commonly used for air conditioning, to help in the starting of the compressor and the condenser fan motor. Dual capacitors come in a variety of sizes, depending on the capacitance (µF), such as 40 plus 5 µF, and also the voltage. A 440 volt capacitor can be used in place of a 370 volt, but not a 370 in place of a 440 volt. The capacitance must stay the same within 5% of its original value. An oval dual run capacitor could be used instead of a round capacitor, but the mounting strap should be changed to better fit the oval shape.

http://www.jbcapacitors.com/Plastic-Film-Capacitors/JFS-Motor-Capacitor.html

IEC/EN 60252-1 2001 specifies levels of protection for motor run capacitors
• P0 - no protection
• P1 - fail open circuit or short circuit
• P2 - fail open circuit only