Auto-Zone Control Systems Auto-Zone Plus Systems Installation & Operation (Version 03A) - Manual (Page 110)

Section 3 Auto-Zone Plus
3-24 Programming
Setpoint Screen #8
Setpoint Screen #9
CW VALVE SETPOINTS
PID Calculation Rate
Enter Period: 15 Sec
CW VALVE SETPOINTS
Kp Constant..: 20
Ki Constant..: 5
Kd Constant..: 20
If you have configured your unit for a Cooling Valve this
screen will appear. The PID control positions the chilled
water valve based on how far the supply air is from setpoint
and the current position of the valve. It looks at the position
of the valve at timed intervals, this interval is set by the PID
Calculation Rate.
Minimum Default Maximum
Calculation Rate 5 Sec 15 Sec 60 Sec
If you have configured your unit for a Cooling Valve this
screen will appear. The Kp Constant is “proportional”
constant which means how many degrees from setpoint will
make the valve open 100%. For example if the Kp is set for
10 then a 10
° temperature rise above setpoint, would cause
the chilled water valve to go 100% open. Ki Constant is the
“integral” constant which prevents the valve from stopping at
a point where the proportional error is not changing. The
amount of the Integral can have is limited by the Ki constant.
Kd Constant is the “derivative” constant. This is used to
track the rate of change in temperature error from setpoint. If
the last change was small, the derivative would have very
little effect since the (error – old error) subtraction would be
a small value. If the last error was large, indicating the
temperature was rapidly moving toward or away from the
setpoint, the valve position would make a large adjustment.
Minimum Default Maximum
Kp Constant 1 20 100
Ki Constant 1 5 100
Kd Constant 1 20 100