Lennox Prodigy 2.0 Application Manual page 48

9.4.2.5. Tuning
In the event that the PID loop requires tuning, the following two methods are recommended depending on the severity of the
problem:
1. In most cases the parameters will only need a small adjustment. In that case use the following table as a basic guide.
Change Desired
Reduce Response time
Reduce Overshoot
Reduce Settling Time
Reduce Offset (steady state error)
2. If method 1 adjustment does not stabilize the system, you may use the following tuning method:
NOTE ­ To use this method the system must be allowed to operate at the manual reset value (% output) without damaging
the system.
A Set the Parameters 31, 32 and 33 blower PID constants to 0 (OFF).
B Start system. Analog output value will be at the Parameter 41 (BLOWER MANUAL RESET) value (%).
C Monitor system. System should be stable. If system is not stable at this point check for other problems. Adjusting
the PID parameters will not solve this problem.
D If system is stable, gradually increase the Parameter 31 (BLOWER PID P CONST) until system starts oscillating
(moving above and below set point, continuously).
E Reduce the Parameter 31 (BLOWER PID P CONST) to 40­70% of the value set in step D.
F Gradually start adding some Parameter 32 (BLOWER PID I CONST) by setting to 127 and reduce setting until the
steady state error (offset) is reduced to an acceptable level.
G If necessary, increase the Parameter 33 (BLOWR PID D CONST) to reduce overshoot. Use of Parameter 33 (D)
can increase settling time and/or lead to instability.
NOTE ­ In most cases, it is best to not use any Parameter 33 (BLOWR PID D CONST).
Table 41. Tuning
Parameter 31
PID P
Increase
Decrease
­
Increase
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Parameter 32
PID I
Decrease
Increase
Decrease
Decrease
Parameter 33
PID D
Decrease
Increase
Decrease
­