Common bypass valve control

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

-