Hello !
The idea is to heat greenhouse with stable temp at 13*C.
Heating method is with circulating hot water(80*C) true pipe, and open/close three-way valve.
Output 1 is for open big circul
Output 2 is for close big circul
valve is 50 mm , step is 10 mm per minute
In theory water heater start at temp 15*C to be prepear and for about 40 min is ready with 80*C .
Temp is continue droping and at 14*C three-way valve start to open circul 1(big one) and need to open 10 mm
After 0.2*C drop down open 10mm again ...
and when temp is drop to 13*C 3-way valve need to be open at all 50mm ...
So the greenhouse is big ( arount 10.000 sq.m. )
And temp continue drop(or not) but in fact is drop to arount 12,5*C to 12*C and stop.
When greenhouse start heating. Temp is start to go up.
3-way valve need to start closeing,and at temp 13*C need to be fully close.
Problem is that : when temp is going up Delta DT320 is operating at the same time OUT1(because temp is lower then 13) and the same time OUT2 is try to close, so the 3-way valve stay at the same place and not closing because is have "line" on open and "line" for close.
setting from Delta DT320
Control
Ctrl Method : PID
RUN/STOP : RUN
Heat/Cool : Heat(out1)/Cool(out2)
Com Write : enable
Lock status : normal
AT : Stop
SV control : Const SV
Input
Type : 4-20mA
Unit : EU
SV : 13.0
Range Hi : 50
Range LO : -20
Pointer : 1
PID Parametyer
Pb : 0.2
Ti : 787
Td : 196
Ctrl Period : 20
I offset : 0.0
PID set : AUTO
PID SV(auto) : 100.0