VLV_CTL Valve Control - Operation Manual - EM1.8U - ELC.E14 - EM1.8D - EM1.8R

Description

VLV_CTL controls an analog cooling/heating valve. In a two-pipe air conditioning unit coil application, cold water passes through the cooling coil in summer to cool the space, and hot water passes through the heating coil in winter to heat the space. The valve generates a PID output based on the current temperature and setpoint. The function block set also has a low limit temperature protection function that requires the heating valve to be fully open for winter heat and freeze protection.

Of all the inputs, Fault Alarm is generated from a PID-adjustable primary sensor. The PID-calculated output is 0 % in the event of a Fault Alarm.

The set also has a manual override function: The output is "Valve Manual Setpoint" if "Valve Mode Select" is "0 - MAN (manual)" and the automatic logic value of the application if "Valve Mode Select" is "1 - AUTO".

Note: PID control of cooling in summer is direct-proportional and that of heating in winter is inverse-proportional.

Function

"Valve Adjustment Control" is calculated based on PI control, ranging from "Minimum Output" to "Maximum Output" when "Fan Command" is "1" (0-OFF/1-ON) and "Sensor Fault Alarm" is "0" (0-OK/1-FLT).

"Valve Adjustment Control" is "Valve Manual Setpoint" when "Valve Mode Select" is "0" (0-MAN/1-AUTO).

"Valve Adjustment Control" is 0 % when "Fan Start/Stop" is "0" (0-OFF/1-ON) or "Sensor Fault Alarm" is "1" (0-OK/1-FLT).

"Valve Adjustment Control" is 100 % when heating valve is working and "Low Limit Temperature" is "1".

Note: PID control of cooling in summer is direct-proportional and that of heating in winter is inverse-proportional.

The output priority is: Low limit temperature protection > Manual mode > Sensor fault alarm > Winter/Summer selection in automatic mode > Normal PID calculation output.

Internal logic

Input

Output

Example