Siemens SIMATIC S5 Manual page 104

Calculation of the response value:
Note: despite "residual value processing" the response value should not be more
than 10%. If a greater value is used, unwanted temperature fluctuations can occur,
depending on the controlled system.
Guide values for the response value:
– when using solid state switching devices (triac etc.):
response value = 0%
– when using mechanical switching devices:
response value 3 to 6%
– with 3-step controllers and air cooling (even when using solid state
switching devices):
response value 3 to 10% (to reduce wear on the fans)
Byte 30 Minimum jump for 3-step controllers
In this byte, you can read the minimum jump for the temperature setpoint if no
cooling parameters could be calculated during the self-tuning phase of
3-step controllers (see byte 23).
Byte 31 Message number
IP244
C79000–B8576–C860–02
Data Exchange with the Central Controller
4–37