PID problem with CP1L

[Mbel 0]

I am using a CP1L-M. I have a TS001 temp expansion module attached with a J type thermocouple set to deg F and 0-700 (rotary switch to 3). I am trying to control a water heater with the PID in conjunction with the TPO instruction. Problem: My manipulated variable continues to rise in value till it reaches the max value in C+6. EX: If I have 0494 in C+6 then my MV in the PID instruction will climb till it reaches 0FFF then stop. Forever. I have to clear the data area and re-execute the PID instruction. Temps read out fine on my HMI. C to C+8 data as follows: 012C 0064 012C 00C8 0032 0008 1494 0000 1D4C Anyone have similar problem? Fix? Thanks All

[pfort 20]

You say that you have 494 in C+6 and it rise until it reach it. Then you say it reach 0FFF. When you monitor the output of the TPO instruction, it should pulse when your MV is low, then stay ON when your MV is high. What do you see there? And when the output of your TPO is ON you should have your ...SSR??, contactor ??? ON. Does it? If yes, does the PV rise ? It is normal that the MV rise if the PV doesn't react. Is it possible for you to post your code? Edited 4 Sep 2013 by pfort