The capacitor is an electrical component of an HVAC system


The capacitor is an electrical component of an HVAC system. It is a medium by which energy is stored and either released suddenly or over a period of time.

A capacitor’s role is to ensure a motor starts spinning and spins in the proper direction.

Starting a motor takes more energy than sustaining its momentum once it is running. The capacitor is responsible for ensuring the unit receives that extra burst of electricity needed to get it going.

Capacitors can be made of mica, ceramic, porcelain, Mylar, Teflon, glass, or rubber.

Only the electrical components that cycle on and off in a typical HVAC system require a capacitor. These components include a compressor, condenser fan, and evaporator fan. These components may or may not be present depending on the type of system in place.

Often times a system will use what is known as a dual capacitor. Dual capacitors can run more than one component in an HVAC system; they often serve both the compressor and condenser fan motor. When talking to an HVAC technician, they will refer to the size of the capacitor in microfarads (μF), a unit of measure for electrical storage. This dual capacitor has two different capacitance measurements: 20 μF and 5 μF.

What is the life expectancy of a capacitor?

The life expectancy of a capacitor can vary dramatically. Some will last less than a year and some will serve their purpose for the life of the HVAC unit.

What causes a capacitor to fail?

There are a multitude of reasons why capacitors can fail. The most common is due to a bad power supply or changes and fluxes in power. Power issues will shorten the life of a capacitor. A high number of unit starts and stops can also shorten the life of a capacitor.

How do you repair a failed capacitor?

A failed capacitor is one of the most common issues in HVAC systems. As a result, technicians typically carry various sizes of wholesale capacitors in their service vehicles.

Replacing a capacitor is a fast and frequent job for contractors

Keep in mind: diagnosing and replacing a failed capacitor should take a contractor no more than an hour of labor.


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