Correcting System "Sluggishness - McQuay MicroTech II Operation Manual

"hunting", generally the first step is to slow down the
response by increasing the Integral Time until the system
becomes stable. This may, however, cause "sluggishness" in
the controlled variable approach to the set point during tran-
sient conditions (such as at unit start up).
gishness" occurs after the Integral Time is adjusted, it means
the overall control response is now too "slow" and the
response must be speeded up by reducing the Proportional
Band. When the Proportional band is changed so that the
controlled variable approach to the set point is acceptable, it
may then be necessary to readjust the Integral Time to re-sta-
bilize the control action.
When in doubt, these parameters should be set to the factory
default setting.

Correcting System "Sluggishness"

If the system control is "sluggish", meaning in the controlled
variable approach to the set point during transient conditions
(such as at unit start up) is too slow, this generally means the
overall control response is too "slow."
"sluggishness", the first step is to speed up the overall sys-
tem response by decreasing the Proportional Band so that the
1. Once operating, the system can be checked for sluggish-
ness by changing the set point and measuring the time it
takes for the controlled variable to reach the set point.
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1
If system "slug-
2
To correct system
controlled variable approach to the set point is acceptable.
This may, however, result in system instability ("hunting").
If system instability occurs, the Integral Time should be
increased to slow down the control response and stabilize the
control action.
When in doubt, these parameters should be set to the factory
default setting.
CAUTION
Grossly misadjusting PID parameters can
cause erratic unit operation and equipment
damage.
PID control parameters should only be adjusted
by trained personnel having a thorough under-
standing of how the parameters affect overall
system operation. Generally these parameters
do not need to be adjusted from the factory
default settings.
2. Once operating, the system can be checked for sluggish-
ness by changing the set point and measuring the time it
takes for the controlled variable to reach the set point
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