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  1. 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