How to Choose the Right HVAC Capacitor: MFD, Voltage & Dual vs Single Run

Choosing the correct HVAC capacitor is mostly about matching the electrical rating on the original part. The two numbers that matter most are the capacitance rating in MFD (µF) and the voltage rating.

Match the MFD rating exactly

The MFD value tells you the capacitor's capacitance. A replacement should match the required MFD rating shown on the original capacitor or the equipment documentation. For example, a dual-run capacitor marked 45/5 MFD has one section for the compressor and one for the fan motor.

Voltage can be equal or higher, not lower

A replacement capacitor can generally use the same or a higher voltage rating when the physical size and application are compatible. For example, a properly specified 440V capacitor can replace a 370V capacitor, but a 370V capacitor should not be used where 440V is required.

Dual-run vs single-run capacitors

A dual-run capacitor combines two capacitance values in one can, commonly serving both the compressor and condenser fan motor. A single-run capacitor provides one capacitance value for one motor circuit.

Before ordering

Check the MFD rating, voltage, terminal layout, physical dimensions and equipment requirements. Do not choose a capacitor only because it looks similar.

Shop HVAC capacitors, including dual-run capacitors and single-run capacitors.