TO SWITCH TO A GEOTHERMAL HEAT PUMP
I had wanted a geothermal heat pump for
a long time. I wanted the savings on my electrical bill that
could be realized from geothermal. I sure didn't want to pay a
driller to put in injection wells, so I did it myself, using the
techniques described on these pages.
Using three injection wells drilled using this technique, I installed an open loop
geothermal heat pump system for a for about
$1,000 plus the cost of the heat pump. I already had a supply well
that I used to water the yard. I drilled three injection wells and
installed PVC to run the water from the supply well to the heat pump,
and then on to the injection wells.
In October of 2009 the primary heat heat pump we
use to heat and cool our house died. It had to be replaced. We had
been studying geothermal heat pumps for years and wantedto realize the
savings on our electrical bill that geothermal would provide. We had
already decided on geothermal but if we needed any prodding, the $652 electrical
bill (heat strips only) we got for November certainly helped to solidify our
already had an excellent well. It would produce plenty of water to run a
geothermal heat pump but we needed injection wells to return the water to the
ground after it passed through the heat pump. Here is a crude drawing of the layout of
I needed to install pipe to get water from the
well to the new geothermal heat pump. Then I needed to pipe that same
water to an injection well. I had heard of some injection wells getting
plugged up and losing some efficiency as they aged. To avoid that I
drilled three injection wells using the techniques described in this site.
Two of the injection wells had sufficient capacity to accept the full 12 GPM the
heat pump used. One had 5 GPM capacity. I'm hoping that by
putting in three injections wells, I have a bit of insurance against any
reduction in performance. Too much capacity would be a lot better
in the long run than too little.
Here is a schematic of the piping that
Obviously anyone who says a picture is worth a
thousand words hasn't seen one of my drawings. Hopefully you get the
picture. It was necessary to trench the yard to put the
PVC pipe in. Here are some photographs
You may notice in the photograph
below that I have not filled in the annular space with cement. This was
dumb and because I failed to do it I had to go back and do it later. On an
injection well for a geothermal heat pump system always fill in around the
annular space with cement. This will keep the water that is being
injected back into the ground from coming up around the well pipe.
I finished all the trenching one night about 7:30 pm. That night,
right on schedule, it rained. I was at the point where I was ready to put the PVC pipe in but my
trenches were full of water. My yard has a little tiny bit of topsoil
perched on top of ten feet of clay. It perks almost as slow as a clay bowl.
The next morning I was ready to proceed with the installation of the PVC. I needed to get that water out of the
trenches so I could install the pipe, so...
OK, so I made a
slight mess. Hey, I got the water out of there, didn't I?
Next: I've got some pipe to
put in the trenches. Come on to Part 2 and the story continues. We
are going to save some serious money here soon.