Refrigeration System; Suction Pressure; Discharge Pressure; Superheat - Emerson Liebert Challenger iCOM 3000 Operation & Maintenance Manual

3.4

Refrigeration System

Each month, the components of the refrigeration system should be inspected for proper function and
signs of wear. Since, in most cases, evidence of malfunction is present prior to component failure,
periodic inspections can be a major factor in the prevention of most system failures.
Refrigerant lines must be properly supported and not allowed to vibrate against ceilings, floors or the
unit frame. Inspect all refrigerant lines every six months for signs of wear and proper support. Also
inspect capillary and equalizer lines from the expansion valve and support as necessary.
Each liquid line has a sight glass that indicates liquid refrigerant flow and the presence of moisture.
Bubbles in the sight glass do not indicate a shortage of refrigerant or a restriction in the liquid line.
The moisture indicator changes from green to yellow when moisture is present in the system.
3.4.1

Suction Pressure

Suction pressure will vary with load conditions. The low pressure transducer will shut the compressor
down if suction pressure falls below the cut-out setting. High suction pressure reduces the ability of
the refrigerant to cool compressor components and can result in compressor damage.
NOTE
Liebert Challenger 3000 fan coil units do not monitor suction pressure using a transducer. On
these models, low-pressure management is accomplished using freeze stats located on the
evaporator coil. See the Liebert iCOM
Additional low-pressure management routines may apply during compressor start and normal
operation. See the Liebert iCOM user manual, SL-18835, for more information. The document is
available on Liebert's Web site:
3.4.2

Discharge Pressure

Discharge Pressure can be increased or decreased by load conditions or condenser efficiency. The high
pressure switch will shut the compressor down at its cut-out setting. Refer to Table 3, below.
Table 3 Discharge pressures
System Design
Air-Cooled
Water/Glycol-Cooled
Maximum
High Pressure Cut-Out
3.4.3

Superheat

Superheat can be adjusted by the Thermostatic Expansion Value (TEV). 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 bulb location and 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.
www.liebert.com
Discharge Pressure
° °
65-75 F (18-24 C) fluid
° °
85
F (29 C) fluid
115°F (46°C) fluid
Component Operation and Maintenance
user manual, SL-18835, for more information.
®
PSIG (kPa)
295 (2035)
239 (1650)
255 (1760)
335 (2310)
365 (2516)
400 (2760)
11
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Liebert ® Challenger 3000