Emerson Liebert CRV, User Manual

Page: 170 / 192

Calibration and Regulation after Startup
Liebert
®
CRV
™
160
15.0 C
ALIBRATION AND
R
EGULATION AFTER
S
TARTUP
The Liebert CRV has been factory-tested and calibrated, but it is very important to check, at startup,
the superheating of the thermostatic valve (A/W versions).
• For calibrations of instruments installed on the external condensers/drycoolers, refer to the
manual for the equipment.
• For control system calibrations, refer to the Liebert iCOM
®
manual, SL-18835. (To prevent erratic
operation, do not use temperature and relative humidity setpoints/proportional bands that differ
excessively from the default settings.)
15.1 Thermostatic Expansion Valve
The Thermostatic Expansion Valve (TEV) performs one function: It keeps the evaporator supplied
with enough refrigerant to satisfy load conditions. It does not effect compressor operation.
Proper valve operation can be determined by measuring superheat. The correct superheat setting is
between 10 and 20°F (-12 and -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.
15.1.1 Determine Suction Superheat
To determine superheat:
1. Measure the temperature of the suction line at the point the TEV 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.
15.1.2 Adjust Superheat Setting with the TEV
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.
15.2 Environmental Protection
Misuse or incorrect calibration of the unit leads to increased energy consumption, resulting in
economic and environmental damage.
15.3
Calibrating Electrical Components
NOTE
Make no more than one turn of the stem at a time. As long as thirty minutes may be required
for the new balance to take place.
Table 38 Calibrating electrical components
Refrigeration Circuit
Item No. Component Setting Notes Contact
18-19
High Pressure
Transducer
Range 045 barg
Output 05V
See Liebert iCOM
®
User Manual, SL-18835
—
14
Low Pressure
Transducer
Range 017.3 barg
Output 05V
—
3
High Pressure
Switch (HP)
STOP 38.7±1 barg
START 30.0±1.5 barg
(fixed setting manual reset)
Reset
Normally
Closed
—
Clogged Filter
Differential Pressure
Switch (CF)
Setpoint range 0.54 mbar
Filter G4 = 2 mbar
Setting Ring
Normally
Closed