Danfoss VLT FC 102 Programming Manual page 454

Programming Guide | VLT® HVAC Drive FC 102
Transmitted over various serial communication protocols.
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The drive can be configured to handle multi-zone applications. 2 different multi-zone applications are supported:
Multi-zone, single setpoint
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Multi-zone, multi-setpoint
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Examples 1 and 2 show the difference between the 2 applications.
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 parameter 20-20 Feedback Function to [3] Minimum
and entering the desired pressure in parameter 20-21 Setpoint 1. If any feedback is below the setpoint, the PID controller increases the
fan speed. If all feedbacks are above the setpoint, the PID controller decreases the fan speed.
Damper
Cooling/
heating coil
Damper
Damper
Figure 80: Example, Multi-zone, Single Setpoint
Example 2, multi-zone, multi-setpoint
The previous example illustrates the use of multi-zone, single-setpoint control. If the zones require different pressures for each VAV box,
each setpoint may be specified in
parameter 20-21 Setpoint 1
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parameter 20-22 Setpoint 2
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parameter 20-23 Setpoint 3
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By selecting [5] Multi-setpoint minimum in parameter 20-20 Feedback Function, the PID controller increases the fan speed if any of the
feedbacks are below their setpoints. If all feedbacks are above their individual setpoints, the PID controller decreases the fan speed.
20-21 Setpoint 1
Default value: 0 ProcessCtrlUnit
Setup: All setups
454 | © 2024.10
Supply
air fan
Return air fan
P P
VAV
Box
P P
VAV
Box
P P
VAV
Box
Parameter type:
Conversion index:
Parameter Descriptions
Zone 1
Zone 2
Zone 3
Range, -999999.999 -
999999.999 ProcessCtrlUnit
-3
AU430028034214en-001901 / 130R0310