Free hot water is possible in the summer with our heat pump.
Free hot water actually exists in the summer, but first I want to explain how we cool our floors in the summer.
I will have to do some fast talking to explain this free hot water claim, but it really is true. The summer heat brings with it the need for cooling a home. We have found that we can cool our home with cold water circulating in our radiant floors. My wife calls this “Floor Conditioning” instead of air conditioning.
We accomplish this feat by using our heat pump to keep the buffer tank temperature to about 60 degrees. That temperature keeps us above the dew point virtually all the time, so we don’t worry about condensation. What we are really doing is pulling heat out of the floor which is typically in the low to mid seventies that time of year. As the buffer tank rises from the floor water, the aquastat calls for the heat pump to cool the tank water. So you can see that we are reversing the operation of the heat pump by transferring heat from the floor. That heat actually warms the well water going through heat pump primary. The heat pump primary output port dumps the heated well water into the discharge well.
We committed to using the heat pump expecting free hot water to be a nice byproduct.
We ordered our heat pump with a special option called by ClimateMaster the “Desuperheater” or Hot Water Generator. Basically, the hot water generator is a separate heating circuit that always transfers heat from a built-in heat exchanger into an external water circuit. We plan to plumb this feature into our domestic hot water tank soon.
The heat pump transfers heat from cold well water in the winter to heat both the buffer tank and the hot water tank. The heat pump works harder and longer to provide this extra heat to the hot water tank. However, the heat pump heats the hot water tank with about 1/3 as much energy for us as the heating elements in the hot water tank. But even this little energy cost only applies in the home heating season.
A hot water generator option also transfers heat from the buffer tank water when it is being cooled for floor conditioning . This is heat that otherwise goes into heating the well water. In this mode, that heat instead heats the hot water tank “for free!” That means that the energy we are expending to cool the floors is a sunk cost. However, the energy that is heating the hot water tank costs nothing extra.
I have not yet installed this system. You should contact the manufacturer of your heat pump BEFORE you order. You will need to ask them and your installer lots of questions to be sure you understand what is involved. I did not do much of this and am not totally familiar with everything that will be done.