16
K VALUES – AIR FLOW MEASUREMENT
Roof fans are equipped with measuring tubes. The pressure difference
Δpm (Pa) measured from them can, together with the fan-specific k
factor, be used to determine the air flow qv (dm³/s) of the roof fan. The
measuring tubes are in the vertical bracket behind the protective cover
of the fan’s control unit. A manometer can be connected to them. The
measuring tubes are marked with + and -. The k factors specified in
the table apply to air density 1.2 kg/m3 (+20°C). The air flow can be
calculated by using the following formula:
If the temperature of the air to be extracted deviates from +20 °C, the
air flow can be calculated by using the following formula:
air density in the
temperature of the air that
is to be extracted
r
20
= 1.2 kg/m³, r
op
=
qv(dm
3
/s) = k *
√
∆pm
r
op
√
r
20
qv(dm
3
/s) =
* k *
√
∆pm
K value
(r = 1,2 kg/m³)
Vallox Exxeo 150
12,5
Vallox Exxeo 300
16,7
Vallox Exxeo 700
22,2
Vallox Exxeo 1400
44,4
Vallox Exxeo 2100
66,7
Vallox Exxeo 2500
147,2
Vallox Exxeo 4100
147,2
K VALUES
SETUP
Before the starting the fan, ensure that the fan wheel can rotate freely
and that there are no loose or extra objects inside the duct system or
the roof fan. Switch the fan on briefly to check its stable operation. If
everything is OK, the roof fan can be started up.
An uninterrupted power supply to the roof fan (Vallox Exxeo
700–4100) is essential to ensure safe operation to the allowed
minimum temperature of the environment. If the motor does not start
although the power supply is working properly (no setting signal,
mains connection via the activation circuit), heating of the motor is
automatically switched on when the inside temperature of the control
unit goes down to -19°C, and when the temperature has risen to -15°C,
it is switched off again. Heating is implemented with a motor coil; the
power is standardised so that it is not sufficient to run the motor (about
five revolutions per hour). In this way, freezing of the rotor can be
prevented.
SETUP
NOTE
There is a separate
instruction manual
for the control panel
of the Vallox Exxeo
basic and DPC
models.
NOTE
The control voltages
of the Vallox Exxeo
DS (dual speed
converter) model can
be adjusted, when
necessary, from the
potentiometers of
the roof fan control
panel (see the
internal electrical
connections of
the DS model) The
factory settings are 5
V and 10 V.