Step coupler for heat elemets based on % input

Codesys V2.3 🇬🇧
joggvald
2017-07-28
2017-09-15

  • joggvald - 2017-07-28

    Im upgrading a HVAC control system, i found a decent macro but the macro is for liquid heat battery, and this application has electrical.

    I would like to use the % output from the valve controller to trigger the heat elemets. Total heat is 110kw (2 x 7kW + 1x14kW + 1x27kW + 1x55kW)

    All 5 heat elemets ar triggered by DO, what function could i use to calculate wich outputs at a given time will give the most correct DO to activate?

    Example:
    0% = 0kW
    25% = 27kW (only 27kW aktice)
    50% = 55kW (Only 55kW active)
    75% = 82kW (Only 55kW + 27kW) active
    100% = 110kW (all active)

     

  • Anonymous - 2017-08-15

    Originally created by: scott_cunningham

    A late answer, but here is a basic FB that will do it (assumes your command is 0 to 100):

    FUNCTION_BLOCK HeatControl
VAR_INPUT
   CmdSignal : INT := 0;
END_VAR
VAR_OUTPUT
   Heat7KwA : BOOL := FALSE;
   Heat7KwB : BOOL := FALSE;
   Heat14Kw : BOOL := FALSE;
   Heat27Kw : BOOL := FALSE;
   Heat55Kw : BOOL := FALSE;
END_VAR
VAR
END_VAR
(*
0% = 0kW
25% = 27kW (only 27kW aktice)
50% = 55kW (Only 55kW active)
75% = 82kW (Only 55kW + 27kW) active
100% = 110kW (all active)
*)
//turn all off first
Heat7KwA := FALSE;
Heat7KwB := FALSE;
Heat14Kw := FALSE;
Heat27Kw := FALSE;
Heat55Kw := FALSE;
//now see which should be on
IF CmdSignal >= 100 THEN
   Heat7KwA := TRUE;
   Heat7KwB := TRUE;
   Heat14Kw := TRUE;
   Heat27Kw := TRUE;
   Heat55Kw := TRUE;
ELSIF CmdSignal >= 75 THEN
   Heat27Kw := TRUE;
   Heat55Kw := TRUE;
ELSIF CmdSignal >= 50 THEN
   Heat55Kw := TRUE;
ELSIF CmdSignal >= 25 THEN
   Heat27Kw := TRUE;
ELSE
   ; //none
END_IF
 
     

  • joggvald - 2017-08-24

    Thanks for your reply.

    Im sorry if my question wasn't crystal clear.

    I would like a function that calculate all the time and then find the nearest combination to match the requested input.

    Is there any pre-made function for this?

     

  • Anonymous - 2017-08-26

    Originally created by: scott_cunningham

    That is what my function block will do based on your information. Call it every scan with your input and it will turn on or off whatever heaters you need.

     

  • joggvald - 2017-09-15

    This is the solution i came up with, in case someone else need this.
    This function calculates the remaining kW wich are given by Heat7KwA with TRIAC.

    FUNCTION_BLOCK HeatControl
VAR_INPUT
   CmdSignal : INT := 0;
END_VAR
VAR_OUTPUT
   Heat7KwA : BOOL := FALSE;
   Heat7KwB : BOOL := FALSE;
   Heat14Kw : BOOL := FALSE;
   Heat27Kw : BOOL := FALSE;
   Heat55Kw : BOOL := FALSE;
  Triacscaled: INT := 0;
END_VAR
VAR
   Triac : INT := 0;
END_VAR

    Triacscaled := (CmdSignal - Triac) * 100 / 7;
IF CmdSignal >= 103 THEN
   Heat7KwB := TRUE;
   Heat14Kw := TRUE;
   Heat27Kw := TRUE;
   Heat55Kw := TRUE;
   Triac := 103;
ELSIF CmdSignal >= 96 THEN
   Heat14Kw := TRUE;
   Heat27Kw := TRUE;
   Heat55Kw := TRUE;
   Triac := 96;
ELSIF CmdSignal >= 89 THEN
   Heat7KwB := TRUE;
   Heat27Kw := TRUE;
   Heat55Kw := TRUE;
   Triac := 89;
ELSIF CmdSignal >= 82 THEN
   Heat27Kw := TRUE;
   Heat55Kw := TRUE;
   Triac := 82;
ELSIF CmdSignal >= 76 THEN
   Heat7KwB := TRUE;
   Heat14Kw := TRUE;
   Heat55Kw := TRUE;
   Triac := 76;
ELSIF CmdSignal >= 69 THEN
   Heat14Kw := TRUE;
   Heat55Kw := TRUE;
   Triac := 69;
ELSIF CmdSignal >= 62 THEN
   Heat7KwB := TRUE;
   Heat55Kw := TRUE;
   Triac := 62;
ELSIF CmdSignal >= 55 THEN
   Heat55Kw := TRUE;
   Triac := 55;
ELSIF CmdSignal >= 48 THEN
   Heat7KwB := TRUE;
   Heat14Kw := TRUE;
   Heat27Kw := TRUE;
   Triac := 48;
ELSIF CmdSignal >= 41 THEN
   Heat14Kw := TRUE;
   Heat27Kw := TRUE;
   Triac := 41;
ELSIF CmdSignal >= 34 THEN
   Heat7KwB := TRUE;
   Heat27Kw := TRUE;
   Triac := 34;
ELSIF CmdSignal >= 27 THEN
   Heat27Kw := TRUE;
   Triac := 27;
ELSIF CmdSignal >= 21 THEN
   Heat7KwB := TRUE;
   Heat14Kw := TRUE;
   Triac := 21;
ELSIF CmdSignal >= 14 THEN
   Heat14Kw := TRUE;
   Triac := 14;
ELSIF CmdSignal >= 7 THEN
   Heat7KwB := TRUE;
   Triac := 7;
END_IF
     

Log in to post a comment.