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VII. STEP 7 — ADJUST EVAPORATOR-FAN SPEED
Adjust evaporator-fan speed to meet jobsite requirements.
Table 6 shows fan rpm at motor pulley settings, Table 7
shows motor efficiencies and Table 8 gives accessory static
pressure drop. Table 9 shows motor performance. Refer to
Tables 10-29 to determine fan speed settings. Fan motor pul-
leys are factory set for speed shown in Tables 1A and 1B.
To change fan speed:
1. Shut off unit power supply and install lockout tag.
2. Loosen belt by loosening fan motor mounting plate
nuts (see Fig. 34 and 35).
3. Loosen movable pulley flange setscrew (see Fig. 36).
4. Screw movable flange toward fixed flange to increase
speed and away from fixed flange to decrease fan
speed. Increasing fan speed increases load on motor.
Do not exceed maximum speed specified in Tables 1A
and 1B.
5. Set movable flange at nearest flat of pulley hub and
tighten setscrew (see Tables 1A and 1B 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.
3. Make angular alignment by loosening motor from
mounting plate.
To adjust belt tension (see Fig. 34 and 35):
1. Loosen fan motor mounting plate nuts.
2. Units 090,091,102,103 — Slide motor mounting plate
away from fan scroll for proper belt tension (
1
/
2
-in.
deflection with 8 to 10 lb of force) and tighten mount-
ing nuts (see Fig. 34).
Units 120,121,150,151 — Slide motor mounting plate
downward to tighten belt tension (
1
/
2
-in. deflection
with 5 to 10 lb of force). Secure motor mounting plate
nuts. See Fig. 35.
3. Adjust bolt and nut on mounting plate to secure
motor in fixed position.
4. Check pulley alignment and realign pulleys if
necessary.
MOTOR MOUNTING
PLATE NUTS
Fig. 34 — Typical Belt-Drive Motor
Mounting for Sizes 090,091,102,103
Fig. 35 — Typical Belt-Drive Motor
Mounting for Sizes 120,121,150,151
Fig. 36 — Evaporator-Fan Pulley Adjustment