A customer has a 45' deep well with a water level at 15'. The Geo system requires 8-15 GPM at 20 PSI. The house requires about 5 GPM at 50 PSI. Using the smallest pump that will deliver the flow required is the most efficient system. Also using a submersible with a good drop in horsepower at low flow rates will help with efficiency. A Grundfos 16S05-5 is a 1/2HP that can deliver 20 GPM at 20 PSI from a depth of 24' using a CSV set at 20 PSI and a 10/30 pressure switch setting. And when restricted with a CSV to supply the 8 GPM heat pump zone that pump will only be drawing about 1/3HP load. This would be the smallest pump using the least amount of energy possible for the Geo system.
When the house needs water an additional 1/2HP jet pump can draw from the same line as the heat pump. The jet pump will pick up the 20 PSI delivered by the well pump and boost the pressure to 50 PSI for the house. So both pumps will run when the house needs water, but the little well pump will be running by itself when only the heat pump is being used. The house will only use water maybe 30 minutes per day, which is the only time both pump will be running. The heat pump could run for many hours per day while the little 1/2HP will be easing along at a 1/3HP load.
This two pump system allows the heat pump to work at 20 PSI and use the smallest and most efficient pump, while the extra pump comes on to boost the pressure when the house needs water. See the following drawing.
When the house needs water an additional 1/2HP jet pump can draw from the same line as the heat pump. The jet pump will pick up the 20 PSI delivered by the well pump and boost the pressure to 50 PSI for the house. So both pumps will run when the house needs water, but the little well pump will be running by itself when only the heat pump is being used. The house will only use water maybe 30 minutes per day, which is the only time both pump will be running. The heat pump could run for many hours per day while the little 1/2HP will be easing along at a 1/3HP load.
This two pump system allows the heat pump to work at 20 PSI and use the smallest and most efficient pump, while the extra pump comes on to boost the pressure when the house needs water. See the following drawing.