Circulating Pump

In selecting the circulating pump, remember it must have enough power to overcome the resistance to flow through the:

  • Ground heat exchanger and headers,
  • Heat pump ground water heat exchanger, and
  • Equipment room piping, including all fittings and hoses.

The circulating pump selected should provide a flow of fluid through the ground source loop adequate to maintain good heat transfer in both cooling and heating modes.

For Residential and small Commercial Installations, many heat pump manufacturers offer standardized pump modules that include the circulator and the necessary valves for system charging, maintenance, and operation.

Proper hookup of the circulating pump, single heat pump, and ground heat exchanger is important. The two ball valves with barbed adapters are included to fill, flush, and pressurize the system.

Temperature and pressure ports should be included at the heat pump inlet and outlet. "Pete's Port" taps are often used to reduce the cost and number of fittings needed.

Where multiple heat pumps are used, multiple circulating pumps, or a single pump with a standby pump can be used. Plotting the curves of the loop and loop plus heat pump, with the circulating pump performance, help in understanding the relationships. The flow rate must be kept out of the laminar flow region and within the manufacturer's data range.

Here, a nominal 33,000 BTUH heat pump system with water at 60°F and 20% calcium chloride at 30°F are plotted against two possible pump selections. The smaller CIR 26-64 would be selected, if the minimum temperature was such that water would be used. If antifreeze must be used, either one would work. In this case, the larger CIR 26-96 is recommended since the capacity of the heat pump increases about 3% when the flow is increased from 7 to 9 gpm.