EDMMT712101 Appendix
VAM-HVE/HVLT Series 175
17.3 Fan Type and Features
17.3.1 Axial and Centrifugal Fans
Ventilators employ both axial and centrifugal fans, and the fans are used separately according to conditions and application.
Axial fans are propeller type fans that can obtain a large airflow rate but they have weak pressure and are used for static pressure of
0-30 Pa. Centrifugal fans are sirocco and turbo types. Both have strong pressure and are used in duct type ventilation.
17.3.2 Model Selection by Impeller Features
Propeller-type ventilators are weak against wind pressure (static pressure) and the airflow rate decreases remarkably when against
the wind.
Differences for changes in airflow rate for wind pressure propellers and sirocco are expressed in a table below.
Although there are differences according to regions and environments, the general aim for propeller type is up to 2 steps and a
pressure type ventilator for above that should be used.
*Even for detached houses, a pressure-type is necessary for rooms that don’t face exterior walls or places in which the outside wind
is strong.
Air Velocity and Wind Pressure (Reference Values)
Propeller Fan
• The axial blower is extremely small and
simple. Although airflow rate is large,
because static pressure is relatively low
at 0-30 Pa, airflow rate substantially
decreases when airflow encounters
resistance such as from a duct.
Sirocco Fan
• Sirocco fans have multiple blower
impellers facing forward in a vane wheel
as shown in the drawing and operate on
a principle similar to water mills. They are
used in all kinds of blowers and are
suitable for high static pressure.
<Features>
• Airflow rate is greater than that of sirocco
and turbo fans and suitable for low static
pressure.
<Installation Place>
• Exterior wall such as for a detached
house
<Application>
• General ventilator • Window ventilator
• Living room ventilator
<Features>
• More suitable than propeller fans for high
static pressure and low airflow rate
<Installation Place>
• Apartment complexes
• Ventilator for ducts
<Application>
• Air conditioning ventilator
• Ventilator for ducts
• Deep range hood
• Intermediate duct fan
• Sirocco fan
Motor
Blade
Axial direction
Blade
Outdoor air velocity V (m/sec)
0
3
5
7
10
15
20
Wind pressure P (Pa)
0
3.9
10.8
20.6
43.1
96.0
171.5
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