AUX EL Series Betriebsanleitung PDF herunterladen (Seite 14)

09/11/2014 12 NI401

Open Loop Well to Well – An open system gets its name from the open discharge of water after it has been

used by the heat pump. A well must be available that can supply all of the water requirements of the heat pump

along with any other water requirements drawing off that same well. The well must be capable of supplying the

heat pumps required flow rated for up to 24 hours per day for the coldest winter day.

Figure 6 shows the necessary components for water piping of an open system. First a bladder type pressure tank

with a “draw down” of at least 1-1/2 to 2 times the well pump capacity must be installed on the supply side of

the heat pump to prevent short cycling the well pump. Shut off valves and boiler drains on the entering and

leaving water lines are necessary for future maintenance. A screen strainer is placed on the supply line with a

mesh size of 40 to 60 and enough surface area to allow for particle buildup between cleanings. Pressure

temperature (P/T) plugs are placed in the supply and discharge lines so that thermometers or pressure gauges

can be inserted into the water stream. On the well water discharge side of the heat pump a flow control/shut off

valve must be mounted to regulate the maximum water flow through the unit. Remove handle to prevent

accidental change of flow.

A solenoid valve is then installed and wired to the compressor contactor terminal on the heat pump. This valve

will open when the unit is running and close when the unit stops. A visual flow meter is then installed to allow

visual inspection of the flow requirements. The flow meter can also be useful in determining when maintenance

is required. Schedule 40 PVC piping, copper tubing, polyethylene or rubber hose can be used for supply and

discharge water lines. Limit rubber hose to 10ft. (305 cm) to prevent excessive pressure drop. Make sure line

sizes are large enough to supply the required flow with a reasonable pressure drop (generally 1.00” diameter).

Water discharge is generally made to a drain field, stream, pond, surface discharge, tile line, or storm sewer.

CAUTION

Using a drain field requires soil conditions and adequate sizing to assure rapid percolation or the required flow rates will not be

achieved. Consult local codes and ordinances to assure compliance. Do not discharge water to a septic system. The heat pump should

never be operated with flow rates (GPM) less than specified. Operation of the unit with less than required flow rate or no flow may

result in freezing water in the water to refrigerant heat exchanger. This will cause the unit to shut down on low-pressure lockout. If the

unit locks out, verify that the unit has the required flow and reset the unit by shutting off power to the unit for one minute. Do not

continually reset the unit; if the unit locks out more than once call your service professional. Continued reset of the unit can freeze

water inside the water coil to the point of rupturing the water coil (Northern Heat Pump does not warranty frozen coils).

Solenoid Valve Wiring (for Open Loop

Systems)

Locate the compressor contactor in the right-

hand high-voltage side of the control panel.

Wire the solenoid valve as shown in this

diagram.

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AUX EL Series Betriebsanleitung Seite 14