Hello, I´m trying to simulate the control of a heating system. Then end of the control is a PID of the error between a power reference I generated internally for the heating system and the actual power consumption of the heating system. To test this control I want to implement a retard transfer function that simulates the power consumption. The idea is that the power consumption of the heating system will be the output of the PID with a retard of, for example, 5 second. The thing is that I don´t know how to implement this in CODESYS or if it is possible. Any ideas?
Any help will be appreciated.

What about this :
This will introduce some filtering on your value.

rActualPower := rActualPower * 0.99 + rPidOutputPower * 0.01;

You may also do this, but it will surely oscillate and tends not to reflect any real system:

aRrBuffer : ARRAY 1..100 OF REAL; 
---
'Cycle index value
index := index + 1;
If index > 100 Then
    index := 1;
End_If
'Recover stored value
rPidInputPower := aRrBuffer[index];
'Place new command in buffer
aRrBuffer[index] := rPidOutputPower;

Both examples need to be called in a cyclical task, where if we want 5s filtering/delay and 100 records, then the cyclical call time should be 5s/100samples so every 50ms.