[Fan27] Fan, pressure-controlled VSD bypass
Program block, name / node subtype: [Fan27] Fan, pressure-controlled VSD bypass
Library hierarchy: Ventilation and air conditioning equipment
Family: Fan
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Configurator
Program blocks are stored in the library without I/Os. Use the auto-create and auto-connect functions to create I/Os and/or to connect them to the interface blocks, e.g., R_A, CMD_B. Alternatively, take the I/Os from the folder containing the predefined I/Os in the library and/or from the plant and connect them to the interface blocks.
Controls a variable speed fan and performs pressure control.
The program block "VSD Bypass" (VsdBy21) performs a control of the ventilator with constant speed in case of a problem with the variable speed drive.
There is a filter function for the measured value for pressure. However, its time constant is set to a short value, e.g., 1 second. The reason for this is that there is already a pre-filtering with the setting for the COV for the predefined IO, e.g., 5 Pa, and, in addition, the PID controller has a preset neutral zone, e.g., 6 Pa.
A minimum speed, e.g., 10 %, is preset with the property "Controller output minimum" of the BACnet object of the controller. The speed can be adjusted.
In case of smoke extraction, the fan speed is defined by a parameter in the program and is independent of the pressure control. Another parameter in the program defines the reaction of the fan if an alarm occurs during smoke extraction and is preset in such a way that alarms from the fan itself do not stop it. The only exception is the maintenance switch.
All alarms generated from the following options, excluding "Fault" if the VSD bypass is enabled, stop the fan, block its outputs with high priority (priority 5), and shut down the plant.
This program block has the following optional functions:
Option: Air volume flow calculation
Measures the airflow and can generate an alarm (optional) if airflow is missing when the fan must run (AirFlCalc21).
Option: Command (1xBO)
Enables the variable speed drive.
Some fan control units, e.g., some EC motors, only need an analog signal, e.g., 0-10 V, and do not need a binary output.
Option: Differential pressure monitor (1xBI)
Reads the signal from a differential pressure monitor over the fan and generates an alarm if differential pressure is missing when the fan must run.
Option: Fault (1xBI)
Reads the fault signal from the fan control unit and generates an alarm.
Option: Feedback (1xBI)
Reads the feedback signal, e.g., from a fan control unit, and generates an alarm if feedback is missing when the fan must run.
A parameter in the program defines the source for the feedback (from the VSD or fan control unit or from an external source):
0 = Feedback from the VSD
1 = Feedback from external source
Option: Maintenance switch (1xBI)
Reads the signal from the maintenance switch and generates an alarm. If active, then the outputs of the fan are stopped with very high priority (priority 2).
Option: Maximum pressure monitor (1xBI)
Reads the signal from a maximum pressure monitor and generates an alarm.
Option: Pressure increase monitoring
Reads the value from the pressure sensor that is used for control and generates an alarm if differential pressure increase is missing when the fan must run.
Name | Description | Type | Alarm / Notification class | Trend / Type |
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VsdBy | Variable speed control (VSD) bypass | N/A | N/A | |
P | Pressure | AI: Analog input | Yes, 4 | Yes, 2 |
Spd | Speed | AO: Analog output | No | Yes, 2 |
PCtr | Pressure controller | Ctr: Controller | N/A | N/A |
SpP | Pressure setpoint | ACnfVal: Analog configuration value | No | Yes, 4 |
Name | Description | Type | Alarm / Notification class | Trend / Type |
|---|---|---|---|---|
DiffPMon | Differential pressure monitor | BI: Binary input | Yes, 4 | No |
Flt | Fault | BI: Binary input | Yes, 4 | No |
Fb | Feedback | BI: Binary input | Yes, 4 | No |
MntnSwi | Maintenance switch | BI: Binary input | Yes, 5 | No |
PMaxMon | Maximum pressure monitor | BI: Binary input | Yes, 4 | No |
Cmd | Command | BO: Binary output | No | Yes, 4 |
PIncrMon | Pressure increase monitoring | BCalcVal: Binary calculated value | Yes, 4 | No |
AirFlCalc | Air volume flow calculation | [AirFlCalc21] Air volume flow calculation, as a function of differential pressure | N/A | N/A |