Hard start kits: improving energy efficiency after installation

Kickstart_grpby Farhang Biek

Even modern air conditioning units may not be as efficient as they can be because of the elimination hard start devices installed at the factory.  In the past all single-phase A/C, heat pump, and refrigeration compressors were equipped with hard start devices at the factory. Several years ago, manufacturers decided to discontinue that practice for most air conditioners and heat pumps in an effort to reduce costs.

A typical start-up requires four to eight times more current to actually start the compressor than what’s required to run it. With this burst of power comes a surge of heat that accompanies the electrical current. This heat damages the compressor, the terminals, the windings and run capacitor.

However, efficiency can be improved for compressors with the installation of a hard start kit. A hard start kit consists of a mechanical potential relay and a start capacitor that is wired to the A/C and heat pump compressor to aid its startup with maximum efficiency so reaching normal rated speed at up to ten times faster than compressors without hard start device.

During start-up, a typical compressor without a hard start device has an electrical efficiency rating of less than 50%. The compressor has to work much harder and is exposed to a lot of excess heat that is generated with each and every start. With a hard start device installed, the electrical efficiency is boosted to more than 98%, enabling all of the available power to reach the compressor for smooth and fast starts.

The benefits of installing a hard start device are:

  • Extend the life of compressors considerably by bringing them up to full speed much more quickly and efficiently.
  • Assist compressors in starting under very harmful ambient conditions such as low voltage, high head pressures or undersized wiring.
  • Reduced “light flicker” during compressor start-up
  • Lower electric bills for the home owners

The average life of Hard Start Devices is generally 5-7 years or 500,000 starts. Most of hard start devices currently come with a two (2) year warranty.