6. Slide the blower/sled assembly from unit after ensuring that the refrigerant and water piping
are protected from damage.
7. Reinstall by reversing this procedure.
11.2.5 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. Inspect the capillary and equalizer
lines from the expansion valve.
Suction Pressure
Suction pressure will vary with load conditions. Suction pressure normally ranges from 58 psi to 75 psi
(405 kPa to 517 kPa).
Discharge Pressure
The discharge pressure will vary greatly with load and ambient conditions (Table 11.1 below). The high-
pressure switch will shut the compressor down at its cut-out setting.
System Design Discharge Pressure, psig (kPa)
Air-Cooled 200-300 (1380-2070)
Water-Cooled 65 to 85°F water
(18 to 29.4°C)
200-250 (1380-1725)
Glycol-Cooled 250-350 (1725-2415)
High-Pressure Cut-Out 400 (2760)
Table 11.1 Typical discharge pressure
Thermostatic Expansion Valve
The thermostatic expansion valve keeps the evaporator supplied with enough refrigerant to satisfy load
conditions. Proper valve operation can be determined by measuring superheat level. If too little refrigerant
is being fed to the evaporator, then the superheat will be high. Conversely, if too much refrigerant is being
supplied, then the superheat will be low. The correct superheat setting is between 10 and 15°F (5.6 and
8.3°C).
Air-Cooled Condensing Units
Restricted airflow through the condenser coil will reduce the operating efficiency of the unit. Additionally,
it can result in high compressor head pressure and loss of cooling. Using compressed air or commercial
coil cleaner, clean the condenser coil of all debris that will inhibit airflow. In winter, do not permit snow to
accumulate around the side or underneath the condenser. At the same time check for bent or damaged
coil fins and repair as necessary. Check all refrigerant lines and capillaries for vibration and support as
necessary. Carefully inspect all refrigerant lines for signs of oil leaks.
Vertiv | Liebert Mini-Mate2—5 ton User Manual| 77
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