Single Stage vs. Two Stage Geothermal Heat Pumps

A human heart beats constantly and, when it stops, that is a bad thing. The heart is designed to keep going and going and going.The compressor on a geothermal heat pump is designed to do the same thing. It works best when it can run for long periods of time without stopping and even better if it can go continuously. This constant cycle is not as damaging to the compressor as periodic starting-and-stopping is. The more the compressor starts and stops the more damage it takes and the shorter its life span will be.

A single-stage compressor in a geothermal heat pump was, for many years, the only option available. A single-stage compressor would function continuously only during periods of extreme temperature, or, in other words, when the house needed constant heating or cooling to compete with the harsh exterior temperatures. In more mild seasons, the compressor would be forced into start-stop operation as it was less difficult to heat and cool and the system did not need to be in constant operation. This led to shorter compressor lifespans and more frequent repairs.

The two-stage compressor is designed to combat this problem. A two-stage compressor keeps one stage operating almost continuously at lower capacity and rarely, if ever, enters a short-cycle. This helps increase the overall lifespan of the compressor despite the near-constant running time of at least part of the system. That means the compressor will last longer and remove another headache for owners.

Two-stage compressors are not yet installed in every geothermal system sold, since they are, relatively speaking, a new innovation. However, as the technology becomes more and more wide-spread we may eventually see a time in which a two-stage compressor is the default standard and yet another extension is added to the life of the average geothermal heat pump system.