The minimum chilled water flow through the chiller can be maintained by controlling the common bypass valve. When the flow through the chiller decreases, the bypass valve begins to close to force more water through the chiller and less water through the bypass valve. In case of multiple chiller applications, the common bypass valve output of each chiller add-on module must be connected to a MIN statement and the output of the MIN statement must be connected to the valve actuator. In this case, the common bypass valve is controlled by the largest deviation below the chiller flow setpoint. The design flow setpoint is defined by the parameter CBV-01.
The proportional band for the bypass valve is defined by the parameter CBV-02.
Fig. 1. Common bypass valve control
If the chiller is off, the bypass valve output is set to 100%.
If no flow sensor is connected, “ComBypValveCtrl” = 100.
Table 6. Parameter List
Description |
Value Range |
Default Value |
Unit |
CBV-01: chiller flow setpoint |
0...9999 |
10 |
kg/s |
CBV-02: P-band common bypass valve control |
0...9999 |
10 |
- |