[FanGrp24] Fan group, pressure-controlled, 2 fan
Program block, name / node subtype: [FanGrp24] Fan group, pressure-controlled, 2 fan
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 two variable speed fans and performs pressure control.
The fans are preset to be of type 25. We do not recommend changing them to an alternative.
FanGrp24 can be used in two ways:
- If, e.g., Fan 1 has a problem, Fan 2 also stops. The whole fan group reports that there is a fault, and the air handling unit stops. In this case, set "Minimum number of fans in operation" to "2". This is the recommended behavior if there is no mechanical check damper or an optional damper controlled by the program.
- If, e.g., Fan 1 has a problem, Fan 2 continues to operate. Only if both fans have a problem, the whole fan group reports that there is a fault, and the air handling unit stops. In this case, set "Minimum number of fans in operation" to "1". In this case, there must be an equipment part that closes the stopped fan (mechanical check damper or optional damper controlled by the program).
If one of the fans is running and is stopped manually (priority 8), the damper does not close automatically and must be closed manually (priority 8).
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 in every fan and is independent of the pressure control. Another parameter in the program defines the reaction of the fan group in the event of an alarm during smoke extraction and is preset in such a way that alarms from the fan group itself do not stop it. The maintenance switch is the only exception.
All alarms generated from the following options stop the fan group, 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).
Options "Damper 1" and "Damper 2"
Shutoff dampers that block the air flow through the fan (Dmp21). Both options belong together. Select or deselect both options together.
Option: Differential pressure monitor (1xBI)
Reads the signal from a differential pressure monitor over the fan group and generates an alarm if differential pressure is missing when the fan group should run.
Option: Maintenance switch (1xBI)
Reads the signal from the maintenance switch and generates an alarm. If active, then the outputs of the fan group are stopped with very high priority (priority 2).
If the fan group (this option) has one maintenance switch, we recommend deleting the optional maintenance switches on both fans. If each fan has its own maintenance switch, disable this option.
Option: Maximum pressure monitor (1xBI)
Reads the signal from a maximum pressure monitor and generates an alarm.
This is a differential pressure switch mounted near the air handler. It prevents damage to the air ducts.
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 group must run.
Name | Description | Type | Alarm / Notification class | Trend / Type | |
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FanGrpFlt | Fan group fault | BCalcVal: Binary calculated value | Yes, 4 | No | |
Fan1 | Fan 1 | N/A | N/A | ||
Fan2 | Fan 2 | N/A | N/A | ||
P | Pressure | AI: Analog input | Yes, 4 | Yes, 2 | |
SpP | Pressure setpoint | ACnfVal: Analog configuration value | No | Yes, 4 | |
PCtr | Pressure controller | Ctr: Controller | N/A | N/A | |
Name | Description | Type | Alarm / Notification class | Trend / Type | |
|---|---|---|---|---|---|
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Dmp1 | Damper 1 | N/A | N/A | ||
Dmp2 | Damper 2 | N/A | N/A | ||
MntnSwi | Maintenance switch | BI: Binary input | Yes, 5 | No | |
DiffPMon | Differential pressure monitor | BI: Binary input | Yes, 4 | No | |
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 | |
PMaxMon | Maximum pressure monitor | BI: Binary input | Yes, 4 | No | |
In case of missing pressure increase within a defined period, a monitoring event is generated (if this optional element is available).