Top view of roof curb showing duct location – Twin City BCFS Centrifugal Filtered Supply Fans - IM-4300 User Manual
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Twin City IM-4300
4. Belt tension is adjusted at the factory. It should be
readjusted after a break-in period of 24 hours of
actual operation.
5. To adjust belt tension, loosen the hex head screw in
the tab of the motor plate. Snug belts by pulling on
the motor until the belt is tight. Tension is correct if
the belt can be twisted from
1
⁄
4
to
1
⁄
2
turn with mod-
erate pressure at a point midway between sheaves.
6. Belt condition and tension should be checked every
3 to 6 months depending on service. If belt tension
is too tight, there is a possibility of overloading the
motor as well as causing undue belt wear. If the belt
tension is too slack, then the wheel will fall off in
RPM, air delivery will decrease and the belts will wear
quite rapidly.
Figure 2. Opening Location of Duct Adapter Accessory
Figure 1. Typical Installation
X
L
Y
W
Duct
(Customer
Supplied)
Damper*
Duct Flange
By Customer
Duct Adapter
(Align this side with
inlet side of curb)
Apply foam tape to seal duct
to unit to prevent leakage
Roof
Curb
Nailer
Strip
Position duct adapter as shown and secure to nailer strip
with nails in holes provided in duct adapter.
*For a standard gravity (spring return) damper, recess the
damper a minimum of 2" inside the duct in order to clear the
fan outlet. For an optional motorized damper, the damper must
be recessed 12" to allow for clearance between the actuator
and fan outlet.
MODEL
DIMENSION (IN.)
BCFS
W
L
X
Y
140A
8
1
⁄
2
19
1
⁄
2
2
1
⁄
4
7
180A
10
1
⁄
2
22
1
⁄
2
1
7
⁄
8
9
240A
13
11
⁄
16
29
1
⁄
2
1
3
⁄
4
11
1
⁄
2
7. If the air handled by the unit is dust or grease laden,
a regular inspection and cleaning of the backdraft
damper and the wheel will ensure smooth, efficient
operation.
WARNING: Do not replace motor sheave with one larger
in diameter. Do not replace fan sheave with one smaller
in diameter. The sheave ratios are set so that the motor
will not be overloaded within the range of the adjust-
able sheave.
CHECK: Belt tension is adjusted at the factory, but it
should be readjusted after a break-in period of approxi-
mately 24 hours of actual operation.
Figure 3. Location of Fan Outlet
L
Fan Outlet
W
Y
X
Curb
Sq.
Inlet Side of Fan (Provide a min. of 15"
between inlet side and nearest obstruction)
Top View of Roof Curb Showing Duct Location
DIMENSIONS ARE NOT TO BE USED FOR CONSTRUCTION.
MODEL
DIMENSION (IN.)
CURB
SUPPLY
BCFS
W
L
X
Y
SQ.
DAMPER
140A
8
19 2
1
⁄
2
7
1
⁄
4
30 x 30
8 x 19
180A
10
22 2
1
⁄
8
9
1
⁄
4
36 x 36
10 x 22
240A
13
3
⁄
16
29
2
11
3
⁄
4
47 x 47
13 x 29