Well Pump Sizing

Strictly speaking, sizing the well pump is the responsibility of the well drilling contractor. It is important, however, that the HVAC contractor be familiar with the factors that determine what size pump will be required. Rule of thumb estimates will invariably lead to under or oversized well pumps. Undersizing the pump will result in inadequate water to the whole plumbing system but with especially bad results to the heat pump – NO HEAT / NO COOL calls will result. Oversized pumps will short cycle and could cause premature pump motor or switch failures.

The well pump must be capable of supplying enough water and at an adequate pressure to meet competing demands of water fixtures. The well pump must be sized in such a way that three requirements are met:

1.Adequate flow rate in GPM.

2.Adequate pressure at the fixture.

3.Able to meet the above from the depth of the well-feet of lift.

The pressure requirements put on the pump are directly affected by the diameter of pipe being used, as well as, by the water flow rate through the pipe. The work sheet included in manual 2110-078 should guarantee that the well pump has enough capacity. It should also ensure that the piping is not undersized which would create too much pressure due to friction loss. High pressure losses due to undersized pipe will reduce efficiency and require larger pumps and could also create water noise problems.

SYSTEM START UP PROCEDURE FOR OPEN LOOP APPLICATIONS

1.Be sure main power to the unit is OFF at disconnect.

2.Set thermostat system switch to OFF, fan switch to AUTO.

3.Move main power disconnect to ON. Except as required for safety while servicing – do not open the unit disconnect switch.

4.Check system airflow for obstructions.

A.Move thermostat fan switch to ON. Blower runs.

B.Be sure all registers and grilles are open.

C.Move thermostat fan switch to AUTO. Blower should stop.

5.Fully open the manual inlet and outlet valves.

6.Check water flow.

A.Connect a water flow meter to the drain cock between the constant flow valve and the solenoid valve. Run a hose from the flow meter to a drain or sink. Open the drain cock.

B.Check the water flow rate through constant flow valve to be sure it is the same as the unit is rated for.

C.When water flow is okay, close drain cock and remove the water flow meter. The unit is now ready to start.

7.Start the unit in cooling mode by moving the thermostat switch to cool. Fan should be set for AUTO.

A.Check to see the solenoid valve opened.

8.Check the system refrigerant pressures against the cooling refrigerant pressure table in the installation manual for rated water flow and entering water temperatures. If the refrigerant pressures do not match, check for airflow problem that refrigeration system problem.

9.Switch the unit to the heat mode by moving the thermostat switch to heat. Fan should be set for AUTO.

A.Check to see the solenoid valve opened again.

10.Check the refrigerant system pressures against the heating refrigerant pressure table in installation manual. Once again, if they do not match, check for air flow problems and then refrigeration system problems.

NOTE: If a charge problem is determined (high or low):

A. Check for possible refrigerant loss.

B.Recover all remaining refrigerant from unit and repair leak.

C.Evacuate unit down to 29 inches of vacuum.

D.Recharge the unit with refrigerant by weight. This is the only way to insure proper charge.

Manual	2100-532B
Page	34 of 46