Unit Operation; General; Control System; Optiview™ Lt Panel - York YGWH 115 Installation, Commissioning & Operation

6.

Unit Operation

General

Units are designed to work independently, or in
conjunction with other equipment via Modbus building
management systems or other automated control
systems.

Control System

The microprocessor control system is capable
refrigerant circuit control to maintain liquid temperature
within programmed limits, as well as system safeties,
displaying status, and daily schedules.
Remote starting and flow and equipment interlock can
be accomplished by field supplied contacts.
Remote indications of alarms, run status and pump
control are available as outputs.
Compressor starting/stopping and loading/unloading
decisions are performed by the microprocessor to
maintain leaving liquid temperature.
OptiView™ LT Panel
The OptiView™ LT panel enables the user to control
the unit operation either manually or automatically or
via remote communications. In addition, it provides
access to view, change and program parameters and
system commands and view faults through an LCD
touch screen.
All the data is displayed in metric values, in English or
Chinese.
The following sections give an overview of the operation
of the unit and the use of the OptiView™ LT panel.
EN
Form 6S6I-B01C-EOMA-EN (0318)
Start-up
Check the main power supplies to the unit are 'ON', all
refrigerant service valves are open (anti-clockwise one
turn short of fully open) and both chilled and cooling
liquid have a regular flow rate, then press the 'ON/OFF'
key on the OptiView™ LT panel.
The controller will perform a pre-check to ensure that
if there is any the daily/holiday schedule or remote
interlocks to prohibit the unit to run, and all safety
cut-outs are satisfied and the cooling or heating load
is required (i.e. that the chilled liquid temperature is
outside the set limits). Any problems found by the pre-
check will be displayed. If no problems are found and
cooling/heating load is required, the compressor will
start.
Normal Running and Cycling
Once the unit has been started, all operations are fully
automatic. After an initial period at minimum capacity
on the compressor, the control system will adjust the
unit load depending on the chilled liquid temperature
and rate of temperature change. If very little heat load
is present, the compressor will continue at minimum
capacity or perform a cycling shutdown to avoid
overcooling the liquid. In that case, the compressor will
restart automatically when the liquid temperature rise
again.
Once the compressor is running, the evaporated
refrigerant vapour is pumped into the water cooled
condenser, which results in the rise of discharge
pressure.
Once the compressor is running the controller monitors
oil pressure, motor current, and various other system
parameters such as discharge pressure, chilled liquid
temperature, etc. Should any problems occurs, the
control system will immediately take appropriate action
and display the nature of the fault.
After the unit stops, the check valve of compressor may
send out some noises, which is caused by the internal
refrigerant equalizing due to the pressure differential. It
is a normal phenomenon and has no influence on the
performance and reliability of unit.
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