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Important Refrigeration Components
Expansion Valves
Thermal Expansion Valve
Each refrigerant circuit has an adjustable thermal expansion valve (TXV). These are factory
adjusted to their normal rating. Any field adjustment should be to “fine tune” a system that has
stabilized and already has acceptable operating parameters. Adjusting a TXV to produce large
swings in superheat is not recommended.
Proper TXV operation can be determined by measuring superheat. The correct superheat
setting is between 8 to 15°F (4.4 to 5.6°C). If too little refrigerant is being fed to the evaporator,
the superheat will be high; if too much refrigerant is being supplied, the superheat will be low.
To adjust the superheat setting:
1. Remove the adjustment cap from the valve.
2. Turn the adjusting stem counterclockwise to lower the superheat.
3. Turn the adjusting stem clockwise to increase the superheat.
NOTICE: Make no more than one turn of the stem at a time. As long as thirty
minutes (30) may be required for the system to re-stabilize.
Electronic Expansion Valve (Optional)
The Electronic Expansion Valve (EEV) is an option available for this unit. This high efficiency
option provides an Electronic Expansion Valve (EEV) on each circuit in place of the standard
thermal expansion valve (TXV). The EEV controls superheat through the dap4 controls by
actively measuring suction pressure via a transducer attached to the suction line and suction
temperature via a thermal transducer strapped to the suction line. The EEV actively adjusts
the orifice size and resulting mass flow of refrigerant to maintain the superheat set-point.
See Section 7.3 Electronic Expansion Valve Drive (EDV) for detailed information regarding the
EEV.
High Pressure Cutout Switch
Each refrigerant circuit is protected by a high-pressure cutout switch (non-adjustable) with
manual reset button. The switch is typically located in the evaporator near the compressor. The
high-pressure switch rating is:
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