Unit installation

803 C – 01/05 A – pag. 13/17
When the evaporator pressure reaches 0,3 bar, move switch Q0 to the “off” position. Remove the jump.
Close the suction line valve. Remove and replace the filter-drier. Evacuate the lines through the liquid line manual
shutoff valve to remove non condensables that may have entered during filter replacement.
Open the suction line valve. A leak check is recommended before returning the unit to operation.
Electronic expansion valve
The PFS water cooled chiller is equipped with the most advanced electronic expansion valve to achieve precise
control of refrigerant mass flow. As today’s system requires improved energy efficiency, tighter temperature
control, wider range of operating conditions and incorporate new features like remote monitoring and diagnostics,
the application of electronic expansion valves becomes mandatory. PFS’s electronic expansion valve proposes
features that makes it unique: short opening and closing time, high resolution, positive shut-off function to
eliminate use of additional solenoid valve, highly linear flow capacity, continous modulation of mass flow without
stress in the refrigerant circuit and corrosion resistance stainless steel body.
Evaporator
Flooded shell-and-tube evaporator operating with refrigerant in shell and water in tubes. Replaceable water tubes
are fabricated from integral finned copper and mechanically bonded to steel tube sheets. Refrigerant side is
ISPESL, TUV or SDM designed, constructed, inspected and stamped. Water side working pressure is designed for
10,5 bar. Vessels include 1” FPT spring loaded pressure relief valves. Shell and non-connection water heads are
insulated with 3/4” thick closed cell insulation.
Condenser
Shell-and-tube type operating with refrigerant in shell and water in tubes. Replaceable water tubes are fabricated
from integral finned copper and mechanically bonded to steel tube sheets. Condenser is designed to conform
ISPESL. Water side working pressure is designed for 10.5 bar.
Lubrificating oils
Besides lubrificating the bearing and other moving parts, the oil has the equally important task of sealing the
clearances between the rotors and other potential leakage paths thereby improving pumping efficiency; the oil also
assists in dissipating the heat of compression. The amount of oil injected is therefore well in excess of that
required for lubrification alone.
Lubricating oil approved for use with McQuay Screw compressor is POE Emkarate RL220H.
The oil differential pressure switch monitors the pressure differential between oil injection pressure and
compressor suction pressure.
After the compressor has started and been in operation for a short time, allowing sufficient time for the system
pressure differential to become established, the oil differential pressure switch is brought into the safety trip circuit.
Oil is now being supplied to the compressor under the action of the system pressure differential, monitored by the
switch. If the pressure differential falls below the switch contacts ‘ break ’ setting and the oil differential pressure
switch trips and stops the compressor.
Because the oil pressure is generated by discharge pressure, a minimum discharge pressure must be maintained;
this minimum pressure increases as the suction pressure increases in order to maintain the pressure difference
required.
Crankcase and oil separator heaters
The function of the heaters is to prevent oil diluition with refrigerant during compressor shutdown, which would
cause foaming and consequent reduction in lubricating oil flow to the moving parts. Electric heaters are energized
every time the compressor shuts-down.
Warning: Verify the heaters have operated for at least 12 hours prior to start-up.