Technical data

2.9 Evaporator
The evaporator is a shell and tube, flooded type, heat
exchanger with a distributor trough providing uniform
distribution of refrigerant over the entire shell length to
ensure optimum heat transfer. A liquid level sight glass is
located on the side of the shell to aid in determining
proper refrigerant charge.A refrigerant charging valve is
provided.
2.10 Condenser
The condenser is a shell and tube, flooded type, heat
exchanger with a discharge gas baffle to prevent direct
high velocity impingement on the tubes. The baffle
distributes the refrigerant gas flow uniformly over the
entire shell length for optimum heat transfer.A subcooler
section is located in the bottom of the condenser to
provide effective liquid refrigerant subcooling, improving
cycle efficiency. The condenser shell also serves as a
refrigerant receiver to store the system charge during
servicing. Optional manually operated isolation valves
are located at the inlet and outlet of the condenser.
Valves are also provided to facilitate removal of the
refrigerant from the system.
2.11 Refrigerant Flow Control
Sub-cooled liquid refrigerant flows out of the condenser
via the liquid line into the evaporator by differential
pressure. A variable metering orifice controls refrigerant
flow to the evaporator. The orifice is selected based
upon the operating conditions of the unit.
The variable orifice actuator is controlled by the
differential pressure set point that is field programmable
in the control panel.
A liquid level sensor, located in the condenser, detects
the refrigerant level. The refrigerant level in the
condenser is expressed as 0% (minimum) to 100%
(maximum). While the chiller is shut down, an open
signal is applied to the actuator, driving the orifice to the
fully open position. When the chiller is started, a close
signal is applied to the orifice actuator for the duration of
the 'Start Sequence Initiated' period. This positions it to
approximately the 75% closed position prior to starting
the compressor motor. To allow for actuator timing
variances and assure the valve is positioned at the 75%
closed position, the duration of the 'Start Sequence
Initiated' period is programmable.
2.12 Capacity Control
Capacity control is accomplished by using differential
pressure to move the slide valve. As the slide valve is
moved axially between the compressor rotors the
volume of vapour pumped by the compressor is
changed to match the system requirements.
Leaving chilled liquid temperature (LCLT) is
continuously monitored and compared to the LCLT
Setpoint. When the LCLT is outside the range of the
setpoint value a signal is sent to energize the control
block directional solenoid valves.
A slide valve potentiometer is used to provide feedback
to display slide valve position as a percentage of full
load.
2.13 Water Boxes
Removable water boxes fabricated from heavy gauge
sheet steel are fitted to each end of both heat
exchangers, the design working pressure is 10 bar.
Integral steel water baffles are located and welded
within the water boxes to provide required pass
arrangements. Stub-out water nozzle connections with
victaulic grooves are welded to the water boxes. Drain
and vent connections are provided in each evaporator
and condenser water box.
2.14 Control Panel
The York OptiView control panel is a factory mounted,
wired and tested microprocessor based control system.
The panel automatically controls the operation of the
unit in meeting system cooling requirements while
minimising energy usage. For detailed information refer
to the YR OptiView Control Panel Operating
Instructions.
2-4 160.81-ICOM-GB0 (01/02)