Instruction Manual

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
Set
p
oint
Temperature
Undershoot
Set
p
oint
Overshoot