Determining Suction Superheat; Adjusting Superheat Setting With The Txv; Electronic Expansion Valve (Eev) Maintenance - Liebert PX018 Installer's/User's Manual

9.8.1 Determining Suction Superheat

To determine superheat:
1. Measure the temperature of the suction line at the point the TXV bulb is clamped.
2. Obtain the gauge pressure at the compressor suction valve.
3. Add the estimated pressure drop between the bulb's location and the suction valve.
4. Convert the sum of the two pressures to the equivalent temperature.
5. Subtract this temperature from the actual suction line temperature. The difference is
superheat.

9.8.2 Adjusting Superheat Setting with the TXV

To adjust the superheat setting:
1. Remove the valve cap at the bottom of the valve.
2. Turn the adjusting stem counterclockwise to lower the superheat.
3. Turn the adjusting stem clockwise to increase the superheat.
NOTE: Make no more than one turn of the stem at a time. Allow up to 15 minutes of fully loaded
compressor operation before checking superheat or making additional stem adjustments.

9.9 Electronic Expansion Valve (EEV) Maintenance

The EEV controls superheat through the Liebert iCOM™ controls by actively measuring suction pressure
via a transducer attached to the suction-line rotalock and suction temperature via a thermister strapped
to the suction line. The EEV actively adjusts the orifice size and resulting mass flow of refrigerant to
maintain the superheat setpoint (set in Liebert iCOM). The EEV is used in place of the standard thermal
expansion valve (TXV).
WARNING! Risk of electric shock. Can cause serious injury or death. The Liebert iCOM
microprocessor does not isolate power from the unit, even in the "Unit Off" mode. Some internal
components require and receive power even during the "unit off" mode of the Liebert iCOM
control. Open all local and remote electric power disconnect switches and verify with a
voltmeter that power is Off before working on any component of the system.
NOTE: Intermittent loss of subcooling may result in EEV/superheat instability. If superheat instability is
observed, check for proper refrigerant level in receiver (see
for Air-cooled Systems
and superheat remains unstable, then increase superheat setting in the Liebert iCOM to 15°F (8.49°C).
Vertiv | Liebert® PDX™ and PCW™ Installer/User Guide |
on page 35 for the proper charge level). If proper charge is observed in receiver,
Refrigerant Piping Guidelines
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