Calibration And Regulation After Startup; Thermostatic Expansion Valve; 15.1.1 Determine Suction Superheat; 15.1.2 Adjust Superheat Setting With The Tev - Emerson Liebert CRV User Manual

15.0 C
ALIBRATION AND
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
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.
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.
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

Table 38 Calibrating electrical components
Refrigeration Circuit
Item No.
18-19
14
3
—
® ™
Liebert CRV
R
EGULATION AFTER
Component
High Pressure Range 045 barg
Transducer Output 05V
Low Pressure Range 017.3 barg
Transducer Output 05V
STOP 38.7±1 barg
High Pressure
START 30.0±1.5 barg
Switch (HP)
(fixed setting manual reset)
Clogged Filter
Setpoint range 0.54 mbar
Differential Pressure
Filter G4 = 2 mbar
Switch (CF)
160

Calibration and Regulation after Startup

S
TARTUP
manual, SL-18835. (To prevent erratic
®
Setting
See Liebert iCOM
User Manual, SL-18835
Notes Contact
—
®
—
Normally
Reset
Closed
Normally
Setting Ring
Closed