Sequence of Operation for Chillers

Inputs:

• Chilled water supply temperature sensor
• Chilled water return temperature sensor
• Condenser water supply temperature sensor
• Condenser water return temperature sensor
• Ambient air temperature sensor
• Humidity sensor
• Chiller status switches
• Pump status switches

Outputs:

• Chilled water valve actuator
• Condenser water valve actuator
• Chiller compressor control relay
• Chiller fan control relay
• Pump motor control relay
• Alarm and fault signal outputs

Control sequence:

1. The controller reads the input signals from the various sensors to determine the current conditions in the system.
2. If the chilled water supply temperature is above the desired setpoint, the controller opens the chilled water valve to allow more flow through the chiller.
3. If the chilled water supply temperature is below the desired setpoint, the controller closes the chilled water valve to decrease flow through the chiller.
4. If the condenser water supply temperature is above the desired setpoint, the controller opens the condenser water valve to increase flow through the cooling tower or heat exchanger.
5. If the condenser water supply temperature is below the desired setpoint, the controller closes the condenser water valve to decrease flow through the cooling tower or heat exchanger.
6. If the ambient air temperature is below a certain setpoint and the humidity level is within acceptable limits, the controller turns on the chiller fan and allows outside air to be used for cooling instead of mechanical cooling.
7. If the chilled water supply temperature is still above the desired setpoint after step 2, the controller turns on the chiller compressor and begins mechanical cooling.
8. The controller adjusts the speed of the chiller compressor and fan motors based on the load and operating conditions.
9. The controller monitors the status of the pumps and triggers alarms or fault signals if any issues are detected.
10. The controller also monitors the temperature and pressure levels in the system and adjusts the control valves to maintain proper flow and pressure.