Cooling control

The cooling coil normally receives its input signal from the control strategy and transfers it directly to the valve output.


Minimum and maximum limits for actuator position signal

The parameters CLG-02 and CLG-03 define the minimum and maximum valve positions during cooling control.

Set CLG-02 to a value > 0 when DX-expansion valves are used.

With the standard settings of 0 and 100%, the DX valves would close too early due to the supply air temperature minimum limitations and the room temperature would never cool down to the room setpoint.


The following functions override the minimum valve position to zero:



Dehumidification control

The decision for cooling or dehumidification is already made in the control strategy. If a separate dehumidification input is used, then the module will transfer the highest of the two signals (cooling or dehumidification) to the cooling valve output.


           


Ramped opening of the valve at cooling start

On plant start-up and each time the valve opens from 0%,it starts a ramp from 0% to the maximum valve position, with a time constant defined by parameter CLG-01.

The valve output signal will always by the minimum value between the internal cooling signal and the ramp function – see next figure.
This ramped opening prevents excessive disturbance of the chillers load, caused by sudden increases of chilled return water temperature.
The function is also useful when controlling cooling coils by 2-way valves with a high-pressure cooling medium.



Note: To disable this function set the value defined by parameter CLG-01 to 100%.


Description

Default value

CLG-01: valve increase per minute

10 %

CLG-02: valve minimum position

0 %

CLG-03: valve maximum position

100 %