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

Description

This function block set is mainly used to control an analog cooling/heating valve. In a two-pipe air conditioning unit coil application, cold water passes through the independent cooling coil in summer to cool space down; hot water passes through the independent heating coil in winter to heat the space up. The valve generates PID output based on the current temperature and setpoint. The function block set also has a low limit temperature protection function, which 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. Once there is such an alarm, the PID-calculated output is 0 %.

This set also has a manually override function. If "Valve Mode Select" is "0 - MAN (manual)", the output is "Valve Manual Setpoint". If "Valve Mode Select" is "1 - AUTO", the output is the automatic logic value of the application.

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

Function

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

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

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

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

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