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Translation from original instructions
4.7 Air system
4.7.1 Unit fans
The units of the series are equipped with radial fans with reverse blades, with external rotor motor directly coupled to the
impeller. These fans do not need any special maintenance as they do not have any couplings (belts, pulleys).
The fans can be integrated in the unit or supplied in a separate section.
The fans are of two different types, referred to as "AC" and “EC":
- AC: alternating current motor, adjustable speed by means of autotransformer on board the machine. The autotransfor-
mer has different output voltages and can, by changing the wiring, power the motor at different voltages in order to
achieve the required airflow and static pressure performances. The units have a standard default connection which,
nevertheless, may need to be checked and adapted to the specific installation.
-
EC: electronically commutated "brushless” motor. The fan is powered by mains AC voltage, speed control is obtained
via control signal DC 0-10V coming from the microprocessor mounted on board the unit. It is thus possible to set the
required speed directly through the parameter being displayed.
Both motors are equipped with an alarm signal, which in the AC version is in fact equal to the thermal protection, whilst in
the EC version it includes thermal protection, overcurrent, under-voltage, the lack of one or more phases, rotor blockage.
The EC fan is not equipped with a remote control switch and is constantly under tension as soon as the
main switch of the unit is closed.
4.7.2 Air flow sensor / differential fan pressure
The units may be equipped, depending on the options or configurations, with a differential pressure transducer which de
-
tects the pressure difference between the inside and the outside (upstream) of the suction nozzle. The pressure difference
is proportional, for each fan/nozzle pair, to the square root of the pressure difference according to the equation:
Q = n • k • √ΔP
where
Q = total air flow [m3 / h]
n = number of fans in the unit
k = constant according to the fan nozzle
ΔP = pressure difference measured on the nozzle [Pa]
the differential pressure value or air flow rate can be seen directly on the microprocessor’s display. If the unit is equipped
with EC-type fans, the microprocessor will also automatically adjust the air flow.
