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Reco-Boxx ZXR / ZXA / Flat – Operation and maintenance instructions
[03/
2022 ]
6.0 Functions
6.1 Operating mode
There are five main operating modes. The operating mode determines how the airflow or the fan torque is
modulated. The default operating mode is Airflow control. Exceptions are units equipped with backwards
fans without the Constant Air Kit or if Constant Torque mode has been selected in the product setup menu,
in both cases it is the fan torque that will be controlled and modulated.
In all the operating modes, the supply fan(s) will operate as per the assigned mode and parameters. The
exhaust fan(s) will operate according to the chosen percentage of the supply fan (%EXH/SUP ratio). The five
main operating modes are:
• 1 – Airflow control:
Flow control involves operating the air handling unit to keep the pre-set airflow constant. The speed of
the fans is automatically regulated to provide correct airflow even if the filters begin to become clogged,
air terminals are blocked, etc. Airflow control mode is advantageous, since the airflow always is exactly
as it was from the beginning. It should however be noted that everything that increases the pressure drop
in the ventilation system, such as blocking of air terminals and dust accumulating in filters, causes the
fans to run at a higher speed. This results in higher power consumption and may also cause discomfort in
the form of noise. There are three airflow setpoints to be configured by the user (m h K1, m h K2, m h K3).
• 2 – Torque control:
3 torque setpoints to be configured by the user (%TQ K1, %TQ K2, %TQ K3). The setpoint is configured
in % of the maximal torque.
• 3 – Demand control 0 –10 V:
The airflow is controlled by a 0-10 V signal. The control signal is connected to terminals K2&GND. The
assigned supply airflow is set as a percentage of a linear 0-10 V signal. The user defines the link with
4 parameters: Vmin, Vmax, m h Vmin and m h Vmax, applied to the following diagram. The demand con-
trol mode is also available for modulating fan torque instead of airflow (relevant for backwards fans units
without Kit CA). The principle is identical to the demand control mode operation with the difference that
Vmin and Vmax are connected to a %TQ instead of m /h.
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• 4 – Pressure control:
The airflow automatically varies to provide constant pressure in the ducting system. This type of con-
trol is also called VAV control (Variable Air Volume). Pressure on supply: the airflow of the supply fan(s)
is modulated to maintain a certain pressure Setting constant. The pressure is measured by a pressure
sensor located in the supply air duct. Pressure on exhaust: the airflow of the exhaust fan(s) is modulated
to maintain a certain pressure Setting constant. The pressure is measured by a pressure sensor located
in the extract air duct.
• 5 - MODE AUS:
This stops the AHU.
