Replies

1. GBA Editor
   Martin Holladay|Mar 07, 2014 04:43pm|#1

   Charles,
   Contact the manufacturer of your ground-source heat pump (sometimes called a "geothermal" system) to ask whether your equipment is compatible with a desuperheater to supply domestic hot water. Some systems are; others aren't.

2. 
   Charles Rusinak|Mar 08, 2014 06:27am|#2

   martin
   i have a desuperheater in my system, it was my understanding that the superheater only provided hot water in the heat cycle ie winter.
   thanks
   chuck

3. GBA Editor
   Martin Holladay|Mar 08, 2014 07:09am|#3

   Chuck,
   You have it backwards. During the summer, the heat pump tries to get rid of extra heat from the house, so that is when heat is available to heat domestic hot water. Most ground-source heat pumps don't produce any "extra" heat during the winter, since (during the winter season) the heat that is transferred by the heat pump goes to space heating.

   Here is an explanation froma website maintained by the U.S. Department of Energy:

   "For water heating, you can add a desuperheater to a geothermal heat pump system. A desuperheater is a small, auxiliary heat exchanger that uses superheated gases from the heat pump's compressor to heat water. This hot water then circulates through a pipe to the home's storage water heater tank.

   "...In the summer, the desuperheater uses the excess heat that would otherwise be expelled to the ground. Therefore, when the geothermal heat pump runs frequently during the summer, it can heat all of your water.

   "During the fall, winter, and spring -- when the desuperheater isn't producing as much excess heat -- you'll need to rely more on your storage or demand water heater to heat the water. Some manufacturers also offer triple-function geothermal heat pump systems, which provide heating, cooling, and hot water. They use a separate heat exchanger to meet all of a household's hot water needs."