Here's an update to our saga.
I chose the Grundfos Magna 3 circulator for the project. It feeds the Bowman heat exchanger from the geosource heat pump tank. A Pentair i2 then circulates spa [an Endless Pool E7000, 2000 gal.] water through the Bowman EC160 and back to the spa. Both pumps are on the RS-485 loop that is run by the NXP microcontroller.
Here are the pumps. The Grundfus is fed from the left, around the back, goes through the heat exchanger [center, with the red label] and back through the sight glass. There are two temperature probes, one before and one after the HX.
On the rear of the sled is the Pentair, fed from the spa into the right side. It loops up and around to feed the HX. The HX out does a loop-de-loop and goes back to the spa.The reason for the loops is to unload any tension on the HX piping as we had broken a
union earlier from thermal expansion/contraction issues. The output side has 2 more thermal probes.
We disconnected the spa's existing 4KW resistive heater, but sense when it got the call for heat; that tells the
NXP-based controller to initiate heating. [The temperatures shown are in centi-Kelvins; 29946 = 299.46K = 29.31C] With the Bowman HX, we were hoping to get 20KW of heat transfer with 8 gpm through the Magna3 and 52 gpm on the i2; we were pleased to see we got up to 24KW.
Getting the spa into place was another adventure:
60 ton crane. 120 ft boom.
Lift it through trees,
over the fishpond and house; and carefully
slide it into place, with
space to spare. We lowered it onto 1 ft^3 blocks of ice. That let us retrieve the lift straps from around the spa, and s..l..o..w..l..y let it seat itself into place.
Thus far, the only issues have been multiple piping leaks, and when they were fixed, failure to reseat the probes into the wells.
