Unit operation
General
Units are designed to work independently, or in conjunction with other equipment through the
Modbus building management systems (BMS) 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 and pump control are available as outputs.
Compressor starting/stopping and loading/unloading decisions are performed by the
microprocessor to maintain leaving liquid temperature.
Unit operating sequence
The following sequence describes the start-up process after unit power up. When a compressor
starts, internal timers limit the minimum time before another compressor can start.
1. After starting the system, the microprocessor performs a pre-check to ensure that the daily
or holiday schedule and any remote interlocks allow the unit to run, all safety cut-outs are
satisfied, and no faults are unsettled. Any problems identified during the pre-check are
shown on the HMI display.
2. The unit can start automatically based on an internal schedule function, without user or
building management system (BMS) input. When the unit is on, the water pump starts
working instantly and the water valves open. The unit then detects the status of the flow
switch to ensure sufficient liquid flow is supplied. Ensure the water pump is controlled by the
leader chiller unit.
3. If there are no problems, the control system adjusts the unit load depending on the liquid
temperature and temperature change rate. If operating at a high load demand, the controller
increases the speed of the inverter compressor or turns on more compressors. If there is
a low load demand, the inverter compressor may continue to operate at low speed or may
simply stop. If the latter is the case, one compressor restarts automatically when needed.
4. When a compressor is running, the controller monitors discharge and suction pressure and
various other system parameters such as liquid temperature, ambient temperature, and heat
exchanger temperature. If any problems are detected, the control system takes appropriate
action and displays the related fault message on the HMI display.
5. The corresponding EC fans cycle on when the compressor starts in cooling and heating
mode. Fan speed is automatically adjusted based on system pressure, ambient temperature,
and other key parameters.
6. Each system is configured with a main EEV in the liquid line between the condenser and
the evaporator. The device automatically adjusts opening steps to satisfy refrigerant flow
demand, mainly based on the difference between the actual and target suction superheat.
YMAE Air-Cooled Inverter Scroll Chiller and Heat Pump100
To Next Page
Loading...
