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Exhaust Fans and Auxiliary Airflows
Each Exhaust Fan and Auxiliary Airflow can be configured to be present on the BACnet
interface or not. By default all Exhaust Fans and Auxiliary Airflows are enabled on the
BACnet interface and will populate as a separate Device Object with a DNET matching
the configured “BACnet DNET” for the system. The Exhaust Fans and the Auxiliary
Airflows have the same Object list. Below is a description of each fan’s Objects.
Operation Status
The Operation Status is a Binary Value that reports whether the fan is running or stopped.
If the Binary Value is active, then the fan is running.
Fault Active
The Fault Active reports whether there is an active VFD fault on the VFD used for this fan.
If this value is active, then the VFD has tripped due to a fault and is not running.
Clear VFD Fault
If the situation resulting in a VFD fault has been resolved, the VFD still will need its VFD
fault cleared before the VFD will power a fan. The Clear VFD Fault Binary Value can be
used to attempt to clear a VFD Fault. If the Clear VFD Fault Binary Value is set to 1
(active), then the system will attempt to clear the fault on the associated VFD. Reading
the Clear VFD Fault will always return inactive.
NOTE: Clearing a VFD fault when the problem responsible for the VFD fault has not been
resolved can lead to VFD, motor or fan damage.
Maximum Output Frequency
The Maximum Output Frequency lists the maximum speed the fan is allowed to run in
Hertz. This can be used in conjunction with the % Commanded Speed and % Actual Speed
to determine the commanded and actual speed in Hertz.
% Commanded Speed
This is the speed at which the system is commanding the fan to run as a percentage.
% Actual Speed
This is the speed at which the fan is currently running as a percentage. Note there will be
a difference between % Commanded Speed and % Actual Speed during normal operation
due to the ramp up and ramp down timing for the VFD.
