Example 1 – Multi zone, single setpoint
In an office building, a VAV (variable air volume) VLT HVAC Drive 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
Feedback Function
, par. 20-20 to option [3], Minimum, and entering the desired pressure in par.
20-21. 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, par. 20-22 and par. 20-23. 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
*
[Ref
MIN
par.3-02 - Ref
MAX
par. 3-03 UNIT (from par. 20-12)]
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
Feedback Function
, par. 20-20.
NB!
Setpoint reference entered here is added to any other references that are enabled (see par.
group 3-1*).
20-22 Setpoint 2
Range:
Function:
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 description of
Feedback Function
, par. 20-20.
0.000
*
[Ref
MIN
- Ref
MAX
UNIT (from
par. 20-12)]
NB!
The setpoint reference entered here is added to any other references that are enabled (see
par. group 3-1*).
20-23 Setpoint 3
Range:
Function:
0.000
*
[Ref
MIN
- Ref
MAX
UNIT (from
par. 20-12)]
Setpoint 3 is used in Closed Loop Mode to enter a setpoint reference that may be used by the frequency
converter’s PID Controller. See the description of par. 20-20 Feedback Function.
VLT
®
HVAC Drive Programming Guide
3. Parameter Description
MG.11.C5.02 - VLT
®
is a registered Danfoss trademark
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