Capacitors

A capacitor is an electronic or electrical device that stores energy between a pair of conductors. These conductors are usually called "plates".  The way a capacitor behaves is dependant upon its makeup and materials used in construction. Basically, there are two types of capacitors used in HVAC equipment. These are start capacitors and run capacitors.

Capacitors are used in two ways:

• To give an initial start boost to a motor and generally used to start compressors
• To increase run efficiency of the motor on air handler blower motors, high efficiency furnaces and pumps for hot and chilled water.

Unless you are familiar with capacitors, it can be difficult to tell if yours has failed. Typically it will be bulged out on the top and sides and needs to be replaced. You risk electric shock even when your equipment has been turned off, so it is always better to have an experienced HVAC contractor check out the equipment.