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0.5
0.4
0.3
0.2
0.1
0
0
200
400
600
FLOW (CUBIC FEET/MINUTE)
Fig. 32 — Barometric Relief Capacity
VII. STEP 7 — ADJUST INDOOR-FAN SPEED
Adjust indoor-fan rpm to meet jobsite conditions. See Table 5
for fan rpm at motor pulley settings. See Table 6 for motor
performance data. See Table 7 for static pressure drops.
Refer to Tables 8-29 to determine fan speed settings.
For units with electric heating, required minimum cfm is 900
for 548F036; 1200 for 548F048; 1500 for 5548F060 and 1800
for 548F072.
A. Direct Drive Motors
The indoor-fan motor factory speed setting is shown on label
diagram affixed to base unit. If other than factory setting is
desired, refer to label located on motor for motor reconnec-
tion. Insert wire into the speed tap corresponding to desired
speed.
B. Belt-Drive Motors
Fan motor pulleys are factory-set for speed shown in Table 1.
See Fig. 33.
To change fan rpm:
1. Shut off unit power supply. Install lockout tag.
2. Loosen belt by loosening fan motor mounting nuts.
3. Loosen movable pulley flange setscrew (see Fig. 34).
4. Screw movable flange toward fixed flange to increase
fan rpm and away from fixed flange to decrease fan
rpm. Increasing fan rpm increases load on motor. Do
not exceed maximum speed specified in Table 1.
5. Set movable flange at nearest flat edge of pulley hub
and tighten setscrew. (See Table 1 for speed change
for each full turn of pulley flange.)
To align fan and motor pulleys:
1. Loosen fan pulley setscrews.
2. Slide fan pulley along fan shaft.
800 1000 1200 1400 1600
3. Make angular alignment by loosening motor from
mounting.
To adjust belt tension:
1. Loosen fan motor mounting nuts.
2. Slide motor mounting plate away from fan scroll for
proper belt tension (
of force).
3. Tighten nuts.
4. Re-check pulley alignment.
Fig. 33 — Belt-Drive Motor Mounting
Fig. 34 — Indoor-Fan Pulley Adjustment
—
20
—
1
/
-in. deflection with 5 to 10 lbs
2
MOTOR MOUNTING
NUTS AND BOLTS
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