HVAC start capacitor and HVAC run capacitor used in HVAC system

HVAC capacitors are used in HVAC to help electrical motors to start and keep running smoothly. They are low-cost components that come in multiple packages, shapes, and sizes. There are also two types capacitor in the HVAC system. HVAC start and run capacitor.

What are HVAC start fun capacitors?

A start capacitor helps a motor start to turn, while a run capacitor helps it to operate more smoothly.

Motors used in HVAC, such as the condensing fan motors or blower fan motors, sometimes need help to start moving and to stay running at a steady pace, with no heavy up and down spikes.

To do this, HVAC units use what are called start and run capacitors which can add more amps or smooth out voltage spikes.


1. A start capacitor holds a charge to start a motor moving.

2. A run capacitor keeps a motor running smoothly with no big up and down spikes.

Not all motors will have a start or run capacitor, some can start and run by themselves.

Capacitors in HVAC can be separated with two capacitors or can be in a single package.

When they are separate, they are called “single”, and when they are combined into one package, they are called “Dual Round.

Example Dual Round HVAC Capacitor    Example single HVAC Oval Capacitor


Example Dual Round HVAC Capacitor Wiring Diagram

A dual capacitor will have one leg to start the compressor (labeled Herm) and another leg to start the condensing fan motor (Labeled Fan).