Thermcraft XST-6-0-36-3V User Manual
Page 79
Installation and Operation Handbook
Tuning
2408 and 2404 Controller
4-5
Setting the cutback values
The above procedure sets up the parameters for optimum steady state control. If unacceptable
levels of overshoot or undershoot occur during start-up, or for large step changes in
temperature, then manually set the cutback parameters ‘
Lcb’ and ‘Hcb’.
Proceed as follows:
1. Set the low and high cutback values to three proportional bandwidths (that is to say, Lcb
= Hcb = 3 x Pb).
2. Note the level of overshoot, or undershoot, that occurs for large temperature changes (see
the diagrams below).
In example (a) increase ‘
Lcb’ by the overshoot value. In example (b) reduce ‘Lcb’ by the
undershoot value.
Example (a)
Example (b)
Where the temperature approaches setpoint from above, you can set ‘
Hcb’ in a similar
manner.
Temperature
Time
Setpoint
Temperature
Undershoot
Setpoint
Overshoot