Can anyone come up with a good reason to use 2 condenser water pumps for each unit (on supply and return) on a water source heat pump system (geothermal)?
Pressure limitation on the geothermal source piping/tubing? I assume you mean a push-pull setup? Is this a loop in the ground? If so, it may have a significant pressure drop, and they don't want to put it under the high pressure needed to overcome the entire system pressure requirement. All I can come up with! More details please.
I second Ross on that. I've seen the same set up.
Try to select a pump and see what kind of efficiency you will get. Low flow/high head application territory, reduce the head for a better, more efficient pump.
If total system dP were 250 ft, and 125 ft of that were in the well tubing, the first pump only needs to be 125 ft. Pressure in the tubing (at the bottom) would be 125 ft + 250 ft static = 375 ft or 162 psi, which is getting up there. If you tried to push it thru the whole loop with just one pump ahead of the tubing, the pressure at the bottom of the loop would be 250 + 250 static = 500 ft or 220 psi. These are high numbers, but the point is, material limitations may govern.
