Siemens SIMATIC S7-1200 Function Manual page 200

Using PID_Temp
6.5 Multi-zone controlling with PID_Temp
Temporary deactivation of cooling
PID_Temp offers the possibility of deactivating cooling temporarily in automatic mode for
controllers with active cooling (Config.ActivateCooling = TRUE) by setting DisableCooling =
TRUE.
This ensures that this controller does not cool in automatic mode during commissioning while
the controllers of other zones have not yet completed tuning of heating. The tuning could
otherwise be influenced negatively by the thermal coupling between the zones.
Procedure
You can proceed as follows during the commissioning of multi-zone control systems with
relevant thermal couplings:
1. Set DisableCooling = TRUE for all controllers with activated cooling.
2. Set PIDSelfTune.SUT.AdaptDelayTime = 0 for all controllers.
3. Specify the desired setpoints (Setpoint parameter) and start pretuning for heating (Mode
= 1, Heat.EnableTuning = TRUE, Cool.EnableTuning = FALSE) simultaneously for all
controllers.
4. Wait until all the controllers have completed pretuning for heating.
5. Set DisableCooling = FALSE for all controllers with activated cooling.
6. Wait until the process values of all the zones are steady and close to the respective
setpoint.
If the setpoint cannot be reached permanently for a zone, the heating or cooling actuator
is too weak.
7. Start pretuning for cooling (Mode = 1, Heat.EnableTuning = FALSE, Cool.EnableTuning =
TRUE) for all controllers with activated cooling.
Note
Limit violation of the process value
If the cooling is deactivated in automatic mode with DisableCooling = TRUE, this can cause
the process value to exceed the setpoint and the process value limits while DisableCooling =
TRUE. Observe the process values and intervene, if appropriate, if you use DisableCooling.
Note
Multi-zone control systems
For multi-zone control systems, the thermal couplings between the zones can result in
increased overshoots, permanent or temporary violation of limits and permanent or
temporary control deviations during commissioning or operation. Observe the process values
and be ready to intervene. Depending on the system, it can be necessary to deviate from the
procedure described above.
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Function Manual, 03/2017, A5E35300227-AC
PID control