The difference between the two is illustrated by the following examples:
Example 1 – Multi zone, single setpoint
In an office building, a VAV (variable air volume) TR200 system must ensure a minimum pressure at selected
VAV boxes. Due to the varying pressure losses in each duct, the pressure at each VAV box cannot be assumed
to be the same. The minimum pressure required is the same for all VAV boxes. This control method can be set
up by setting par. 20-20
Feedback Function to option [3], Minimum, and entering the desired pressure in
par. 20-21
Setpoint 1. The PID Controller will increase the speed of the fan if any one feedback is below the
setpoint and decrease the speed of the fan if all feedbacks are above the setpoint.
Example 2 – Multi zone, multi setpoint
The previous example can be used to illustrate the use of multi zone, multi setpoint control. If the zones require
different pressures for each VAV box, each setpoint may be specified in par. 20-21
Setpoint 1, par. 20-22 Setpoint
2 and par. 20-23 Setpoint 3. By selecting
Multi setpoint minimum
, [5], in par. 20-20 Feedback Function, the PID
Controller will increase the speed of the fan if any one of the feedbacks is below its setpoint and decrease the
speed of the fan if all feedbacks are above their individual setpoints.
20-21 Setpoint 1
Range: Function:
0.000
Proc-
essCtrlU-
nit*
[-999999.999 - 999999.999
ProcessCtrlUnit]
Setpoint 1 is used in Closed Loop Mode to enter a setpoint reference that
is used by the frequency converter’s PID Controller. See the description
of par. 20-20
Feedback Function.
Setpoint reference entered here is added to any other references that are
enabled (see par. group 3-1*).
20-22 Setpoint 2
Range: Function:
0.000
Proc-
essCtrlU-
nit*
[-999999.999 - 999999.999
ProcessCtrlUnit]
Setpoint 2 is used in Closed Loop Mode to enter a setpoint reference that
may be used by the frequency converter’s PID Controller. See the de-
scription of
Feedback Function
, par. 20-20 Feedback Function.
The set-point reference entered here is added to any other references that are enabled (see par. group 3-1*).
How to program the Frequency Converter
6-50 BAS-SVX19C-EN
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