What are two-stage compressors and variable speed motors?

HVAC manufacturers are constantly engineering new technologies to improve the efficiency of their equipment. Two of those technologies that help keep energy bills down are the two-stage compressors and variable-speed motors.

Two-stage compressor

Two-stage cooling means the air conditioner or heat pump has a compressor with two levels of operation: high for hot summer days and low for milder days. Since the low setting is adequate to meet household-cooling demands 80 percent of the time, a two-stage unit runs for longer periods and produces more even temperatures. This is extremely popular in areas where utility costs are high.

Longer run-times or cooling cycles also translate in to quieter, more efficient operation and enhanced humidity control. Compared to a single-stage unit, a two-stage air conditioner or heat pump can remove much more moisture from the air. This is important because when moisture levels are high, there's a higher potential for mold and other pollutant problems.

Variable speed motors

The indoor air handler (fan and motor) provides the energy to move air through the ductwork of a central air conditioning or heat pump system to the rooms of your house. In most standard central cooling and heating systems, the fan and motor runs at one speed, which means the system is either on or off. A variable speed motor (VSM) uses control technology, meaning the VSM automatically changes speed based on your home’s heating and cooling requirements. It slowly increases up to maximum speed instead of coming on at full capacity all at once. This eliminates the sudden blast of air you feel with a one-speed system and results in the system running at a lower speed most of the time. This eliminates noisy start up, while reducing wear and tear on the fan and motor, resulting in a substantial reduction in operating costs due to major energy efficiency improvements. Essentially, your AC system is going to run less and save you money.