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110
Table 29 —
Belt Drive Plenum Fan Dimensions (in.)
Table 30 —
Direct Drive Plenum Fan Dimensions (in.)
Fan Motors and Drives
When installing motors in the field, locate the electrical junction
box toward the center of the unit. This arrangement is required for
correct belt tension. Use the smallest mounting holes in the
mounting base that will accommodate the motor and provide min
-
imum overhang.
Tighten the motor holddown bolts. Refer to Table 6 for fan scroll
inlet cone dimensions.
JUNCTION BOX CONDENSATE PREVENTION
When air handlers are installed outdoors in a high humidity envi
-
ronment or indoors where the apparatus room is used as a fresh air
plenum, precautions must be taken to prevent condensation from
forming inside the junction box of the internally mounted motor.
Standard installation practice is to mount the motor starter or fused
disconnect box adjacent to the air handler and enclose the power
wiring to the motor in flexible conduit.
The sheet metal housing of the disconnect switch or motor starter
is not airtight (even when a box meeting NEMA [National Electri
-
cal Manufacturers Association] IV standards is used). Thus, warm
moist air can migrate through the flexible conduit to the junction
box on the motor. With the motor located inside the unit, the motor
temperature is that of the cool supply air, so condensate can form
inside the junction box and, possibly, on the live terminal lugs.
To prevent the moist air from migrating through the conduit to the
motor, seal the power wires inside the flexible conduit at the motor
starter or fused disconnect (Fig. 53).
Use a nonconductive, non-hardening sealant. Permagum (manu
-
factured by Schnee Morehead) or sealing compound, thumb grade
(manufactured by Calgon), are acceptable materials.
Motor Power Wiring
The fan section is provided with a decal indicating the recom
-
mended location to drill or punch hole(s) to accommodate an elec
-
trical conduit for the fan-motor wiring. The decal is located on the
motor side, approximately 4 in. in from the side and 4 in. down
from the top of the corner above where the motor will be installed.
Where possible, the conduit should be installed in a panel which
will not be removed, such as the discharge panel.
MOTOR OVERLOAD PROTECTION
Fan-motor starters and overload protectors are field-supplied and
installed. A label on the fan motor indicates the correct size of the
overload protectors required to be installed in the motor starter.
Sheaves
Factory-supplied drives are pre-aligned and tensioned. However,
Carrier recommends checking the belt tension and alignment be
-
fore starting the unit. Always check the drive alignment after ad
-
justing belt tension.
To install sheaves on the fan or motor shaft, remove any rust-pre
-
ventive coating on the shaft. Make sure the shaft is clean and free
of burrs. Add grease or lubricant to bore of sheave before install
-
ing. Mount sheave on the shaft; to prevent bearing damage, do not
use excessive force (i.e., a hammer). Place sheaves for minimum
overhang (see Fig. 54).
Each factory-assembled fan, shaft, and drive sheave assembly is
precision aligned and balanced. If excessive unit vibration occurs
after field replacement of sheaves, the unit should be rebalanced.
To change the drive ratio, reselect and replace the motor sheave,
not the fan sheave.
After 24 hours of unit operation, the drive belts may stretch.
Check the belt tension after 24 hours of operation and adjust if
necessary. Periodically check belt tension throughout the run-in
period, which is normally the initial 72 hours of operation.
FAN
WHEEL
39M UNIT SIZE
LENGTH WIDTH HEIGHT
SUPPLY
RETURN
123
03W
03W
41.0
23.4
23.7
153
06W,08W
06W,08W
42.5
36.0
26.2
163
08W
08W
24.8
46.5
29.1
183Q
10W
10W
26.3
53.3
31.3
223Q
12W,14W,
17W
12W,14W,
17W
29.6
58.3
36.7
243Q
17W,21W
17W,21W
32.6
62.5
40.1
273Q
21W,25W
21W,25W
36.5
66.3
41.4
303Q
25W,30W
25W,30W
38.8
70.3
45.4
333Q
30W,36W,
40W
30W,36W,
40W
41.0
75.8
48.9
363Q
36W,40W,
50W
36W,40W,
50W
48.9
91.4
54.4
403Q
—
40W
48.9
91.4
58.3
50W,61W
50W
57.4
99.4
58.4
443Q
61W
50W,61W
57.4
99.4
64.0
493Q
—
61W
57.4
99.4
70.0
40
72W
72W
34.2
92.2
56.4
44
72W,85W
72W,85W
38.0
100.0
61.4
49
85W,96W,
110W
85W,96W,
110W
41.3
107.8
68.9
55
110W
110W
52.3
114.7
76.4
FAN
WHEEL
39M UNIT SIZES
FAN SLED ASSEMBLY
LENGTH
WIDTH
HEIGHT
105
03W
21.0
19.4
18.2
122
03W
22.5
21.6
20.2
135
06W
23.6
22.7
21.0
150
06W,08W
27.0
25.4
22.9
165
06W,08W
27.8
27.0
24.5
182
08W,10W,12W
31.1
29.1
26.8
200
10W,12W,14W,16T
32.8
31.5
29.5
222
12W,14W,16T,17W,
18T
36.3
34.6
32.0
245
14W,16T,17W,18T,
21W,22T,25T
37.8
37.4
34.9
270
17W,21W,22T,25W,
25T,27T,30W,30T,
35T
40.6
41.0
34.7
300
21W,22T,25W,25T,
30T,36W,37T
46.6
44.7
40.9
330
25W,30W,30T,35T,
40W
48.4
47.9
43.5
365
30W,35T,36W,37T,
40W,50W,61W
51.8
51.4
46.7
402
36W,37T,40W,50W,
61W
54.8
52.3
53.6
Fig. 53 —
Sealing Power Wires in Flexible Conduit
a39-1108tf