Fan Motors And Drives; Junction Box Condensate Prevention; Motor Power Wiring; Motor Overload Protection - Carrier Aero 39MN Series Installation, Start-Up And Service Instructions Manual

Table 29 — Belt Drive Plenum Fan Dimensions (in.)
39M UNIT SIZE
FAN
WHEEL
SUPPLY RETURN
123 03W
153
06W,08W 06W,08W
163
08W
183Q 10W
12W,14W, 12W,14W,
223Q
17W
243Q
17W,21W 17W,21W
273Q
21W,25W 21W,25W
303Q
25W,30W 25W,30W
30W,36W, 30W,36W,
333Q
40W
36W,40W, 36W,40W,
363Q
50W
403Q
—
50W,61W
443Q 61W 50W,61W
493Q —
40 72W
44
72W,85W 72W,85W
85W,96W, 85W,96W,
49
110W
55 110W
Table 30 — Direct Drive Plenum Fan Dimensions (in.)
FAN
39M UNIT SIZES
WHEEL
105 03W
122 03W
135 06W
150 06W,08W
165
06W,08W
182
08W,10W,12W
200 10W,12W,14W,16T
12W,14W,16T,17W,
222
18T
14W,16T,17W,18T,
245
21W,22T,25T
17W,21W,22T,25W,
270 25T,27T,30W,30T,
35T
21W,22T,25W,25T,
300
30T,36W,37T
25W,30W,30T,35T,
330
40W
30W,35T,36W,37T,
365
40W,50W,61W
36W,37T,40W,50W,
402
61W

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.
LENGTH WIDTH HEIGHT
03W 41.0 23.4
42.5 36.0
08W 24.8 46.5
10W 26.3 53.3
29.6 58.3
17W
32.6 62.5
36.5 66.3
38.8 70.3
41.0 75.8
40W
48.9 91.4
50W
40W 48.9 91.4
50W 57.4 99.4
57.4 99.4
61W 57.4 99.4
72W 34.2 92.2
38.0 100.0
41.3 107.8
110W
110W 52.3 114.7
FAN SLED ASSEMBLY
LENGTH WIDTH HEIGHT
21.0 19.4
22.5 21.6
23.6 22.7
27.0 25.4
27.8 27.0
31.1 29.1
32.8 31.5
36.3 34.6
37.8 37.4
40.6 41.0
46.6 44.7
48.4 47.9
51.8 51.4
54.8 52.3
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
23.7
temperature is that of the cool supply air, so condensate can form
26.2
inside the junction box and, possibly, on the live terminal lugs.
29.1
To prevent the moist air from migrating through the conduit to the
31.3
motor, seal the power wires inside the flexible conduit at the motor
36.7
starter or fused disconnect (Fig. 53).
40.1
Use a nonconductive, non-hardening sealant. Permagum (manu-
41.4 factured by Schnee Morehead) or sealing compound, thumb grade
(manufactured by Calgon), are acceptable materials.
45.4
48.9
54.4
58.3
58.4
64.0
70.0
56.4
Fig. 53 — Sealing Power Wires in Flexible Conduit
61.4
68.9

Motor Power Wiring

76.4
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
18.2
will not be removed, such as the discharge panel.
20.2
21.0

MOTOR OVERLOAD PROTECTION

22.9
Fan-motor starters and overload protectors are field-supplied and
24.5
installed. A label on the fan motor indicates the correct size of the
26.8
overload protectors required to be installed in the motor starter.
29.5

Sheaves

32.0
Factory-supplied drives are pre-aligned and tensioned. However,
Carrier recommends checking the belt tension and alignment be-
34.9
fore starting the unit. Always check the drive alignment after ad-
justing belt tension.
34.7
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
40.9
of burrs. Add grease or lubricant to bore of sheave before install-
ing. Mount sheave on the shaft; to prevent bearing damage, do not
43.5
use excessive force (i.e., a hammer). Place sheaves for minimum
overhang (see Fig. 54).
46.7
Each factory-assembled fan, shaft, and drive sheave assembly is
precision aligned and balanced. If excessive unit vibration occurs
53.6
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.
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