Operation and Maintenance (Closed Loop)


After installation, flushing, and testing, and prior to operation, the geothermal heat pump system should be checked out. During its service life the equipment should be properly operated and periodic maintenance performed.

Follow the heat pump manufacturer's checkout list. A system operational checkout typically includes these steps:

Measure the rate of flow of water through the loop system. This can be done using one of two methods.

1. A calibrated flow meter, or

2. The Pressure Drop method. If the latter is used:

  • Measure the water pressure entering and leaving the heat pump's heat exchanger. There should be a small pressure drop or pressure difference.
  • Using manufacturer published data, find the measured pressure drop and read the corresponding flow rate. Typically this should be about 2 to 3 gpm per nominal ton of cooling capacity.

For example, a 3-ton heat pump typically will have about 6 to 9 gpm flow for correct operation. The temperature of the water entering the heat pump should be checked. During heating operation, this should be between 25 to 80°F. During cooling operation, it should be between 40 to 110°F. Once it has been determined that the flow rate and entering water temperature are acceptable, the heat pump system is ready to be turned on and checked for correct operation.

With the thermostat fan position "On," the blower should start. Set the room thermostat for the appropriate mode, cooling or heating, and measure the water and air temperatures. In the cooling mode, there should be about a 10°F difference between the entering and leaving water temperatures. The entering and leaving air temperature difference should be about 16 to 20°F.

In the heating mode, there should be a 4 to 8°F difference between the entering and leaving water temperatures. The air temperature difference in heating should be about 25 to 35°F.

Turn the thermostat to a higher heating setting and check to see that the emergency heat, if installed, operates.

Set the thermostat to maintain the desired comfort level.

Perform the following periodic maintenance procedures at the intervals indicated: Inspect the air filters every three months. The frequency of filter charge-outs depends on the type of occupancy. The units should never be operated without filters in place.

Check the condensate pans for proper drainage and algae growth every three months. When algae growth is apparent, consult a specialist for proper chemical treatment. Typically the application of an algaecide every three months will eliminate most problems.

Have the heat pump system serviced at least once a year. This should include a visual inspection, refrigerant leak test, cleaning the evaporator coil, and a check of the compressor amperage, fan and pump motors. Record these values in a log book so a deteriorating condition can be detected before component failure. Repair any deficiencies noted.

The refrigerant cycle should be serviced by a competent technician, preferably one who is factory-trained to service the actual equipment installed. In all cases, reference should be made to the equipment manufacturers' Operating & Maintenance Instructions - a copy of which should remain with the equipment owner or operator. For more detailed information, refer to the manufacturers' Service Instructions.

During the life of the system, emergency service will occasionally be required. Such servicing usually falls into one of three areas:

1. The electrical wiring and controls,

2. The heat pump unit, and

3. The Loop water system.

Electrical problems are the most common cause of emergency service calls. Trouble shooting a suspected electrical problem typically involves taking voltage readings at key points and comparing them to a normal reading. Non-electric service for Loop water systems should start with checking the flow rate and temperature as outlined in the checkout discussion. Leaks, proper pump operation, and scale in the refrigerant-to-water heat exchanger are the primary concerns. Any discrepancies discovered should be remedied before placing the system back in operation.