How to Make Hot Water With a Geothermal System

Many know that geothermal systems can make hot water but no one seems to understand how it works. Very simply – geothermal systems have a compressor. Whenever the compressor is operating, there is waste heat produced in the refrigeration cycle.  That waste heat can be used to produce domestic hot water.

The hot water generating component of a geothermal system is called a desuperheater. It is merely a pump and a heat exchanger that is plumbed in such a way so as to carry waste heat away from the refrigeration cycle and into your water heater. It does not affect the heat output of the geothermal system in the winter. Geothermal systems have safeguards that prevent the desuperheater from operating when that heat is needed for heating the building.  (For a more vigorous description of superheat, you might enjoy this article.)

A little circulator pump pulls water out of the water heater and pumps it through a heat exchanger where it picks up heat. The warmer water is then pumped back into the water heater.  Here is a very basic sketch showing how a desuperheater works:

When operating, a desuperheater is capable of producing hot water with a temperature of 120F to 150F.  When the compressor is not operating, the system doesn’t make any hot water. The balance of the hot water needs must be made up with gas, electric or some other fuel.  Under typical conditions, a geothermal system will produce about 50% of a home’s annual hot water needs resulting in significant savings over traditional water heating fuels.

Still have questions about geothermal hot water production? Want to know what kind of water heater it will work with? Call or email us for more information.