Vertiv Liebert CRV - Thermostatic Expansion Valve (TXV) Maintenance; Determining Suction Superheat; Adjusting Superheat Setting with the TXV

COMPONENT
MAINTENANCE PERIOD
MONTHLY BY
USER
EVERY
3MONTHS
EVERY
6MONTHS
ANNUALLY
Refrigerating Circuit
Check compressor noise/vibrations X
Check oil level through compressor sight
glass
X
Adjust/tighten compressor/functional
elements
X
Check sight glass for problem detection X
Check starting/running amps X
Check refrigerating circuit main pressures X
Check compressor suction superheat X
Check discharge temperature X
Check subcooling X
Air-cooled
Condenser/Drycooler
(if applicable)
Check fan bearings X
Check fan motor mounts for tightness X
Check coil condition X
Check pipeline supports X
Check fan speed controller operation X
Water/Glycol Pump See manual for the pump
Table 13.1 Maintenance schedule (continued)
13.5.1 Thermostatic Expansion Valve (TXV) Maintenance
The TXV performs one function: It keeps the evaporator supplied with enough refrigerant to satisfy load
conditions. It does not affect compressor operation.
Proper valve operation can be determined by measuring superheat. The correct superheat setting is
found in Superheat and Refrigerant Charge Optimization on page50. 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.
13.5.2 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.
13.5.3 Adjusting Superheat Setting with the TXV
To adjust the superheat setting:
1. Remove the valve cap at the bottom of the valve.
Vertiv | Liebert CRV Installer/User Guide | 136