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Supply
air
Ductwork
The ductwork dimensions should be determined in accordance
with the air flow to be carried, and the available static pressure
of the unit. The different air flows and power input values for
each unit are shown in the fan performance curves.
It is recommended to observe the following considerations:
a)
Whatever type of ductwork is used, it should not be made
of materials which are flammable, or which give off toxic
gases in the event of a fire. The internal surfaces should be
smooth, and not contaminate the air which passes through.
b)
At the points where the ducts join the unit, it is
recommended to use flexible connections which absorb
vibrations, prevent noise inside the ductwork and allow
access to the unit (see Fig. 36).
c)
Bends near the unit outlet should be avoided as much as
possible. If unavoidable, they should be as slight as
possible, and internal deflectors should be used when the
duct has large dimensions.
d)
The installation of baffles in the supply air outlet ducts
significantly dampens the noise created by the air flow.
e)
The ratio between the duct sides should not exceed 1:3
(rectangular ducts).
Flexible joint
Return air
Fig. 36 - Side view
f)
Adjust the belts and pulleys to obtain air flows and static
pressures that differ from the nominal values, if required.
The units are factory-set to supply nominal air flow and
nominal static pressure, as shown in Figs. 10 to 16.
Return
air
NO
YES
Fig. 35
Supply air
Unit
When indoor pressure and air flow requirements differ from
nominal ratings, the motor pulley can be adjusted for different
available static pressure values :
1.
Move the motor along its track in order to remove the belt
(ver Fig. 37).
2.
Loosen the pulley setscrews
3.
Tighten the setscrews
4.
Replace the belt(s) in the channel of the pulley.
5.
Tighten the belt(s), using the tension screw nut and washer
(see Fig. 38).
6.
Check the new fan speeds with a tachometer.
7.
After the first operating hours, check the belt tension and
if necessary retighten the belts (see Fig. 38).
Setscrews
Motor pulley
Motor
Belt
Tensioning screw
Align the pulleys using a ruler.
To align fan and motor pulleys:
1.
Loosen fan pulley setscrews. Slide fan pulley along the
pulley shaft and align with the motor using a ruler, making
sure that it is parallel to the belt.
2.
Tighten the fan pulley setscrews.
To adjust the belt tension, loosen the motor mounting plate
bolts and slide the motor mounting plate until the belt is
tight.
and rotate as necessary.
.
Motor support
Fig. 37
1
Fixed flange
2
Setscrews
3
Movable flange
4
Straight-edge must be parallel with belt
5
Motor and fan shafts must be parallel
6
Pulleys
7
Motor and fan shafts must be parallel
Fig. 38
27
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