Indoor Airflow And Airflow Adjustments - Bryant 551B Series Installation, Start-Up And Service Instructions Manual

IV. INDOOR AIRFLOW AND AIRFLOW ADJUSTMENTS
CAUTION: For cooling operation, the recommended
airflow is 300 to 500 cfm per each 12,000 Btuh of rated
cooling capacity. For heating operation, the airflow must
produce a temperature rise that falls within the range
stamped on the unit rating plate.
Adjust evaporator-fan speed to meet jobsite conditions.
Table 4 shows fan rpm at motor pulley settings. Table 5 shows
maximum amp draw of belt drive motor. Refer to Tables 6-13
to determine fan speed settings.
For units with electric heating, required minimum cfm is 900
for 551B036; 1200 for 551B048; 1500 for 551B060; and 1800
for 551B072.
A. Belt-Drive Motors
Fan motor pulleys are factory-set for speed shown in Table 1.
Check pulley alignment and belt tension prior to start-up.
To change fan speed:
1. Shut off unit power supply.
2. Loosen belt by loosening fan motor mounting nuts. See
Fig. 26.
3. Loosen movable pulley flange setscrew (see Fig. 27).
4. Screw movable flange toward fixed flange to increase speed
or away from fixed flange to decrease speed. Increasing
fan speed increases load on motor. Do not exceed maxi-
mum speed specified in Table 1.
5. Set movable flange at nearest keyway 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 (see Fig. 27):
1. Loosen fan pulley setscrews.
2. Slide fan pulley along fan shaft.
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 ( 1 ⁄ -in. deflection with one finger).
2
UNIT
551B
0 1 ⁄
2
036 1090 1055
048 1185 1150
060 1460 1425
072 1585 1540
*Approximate fan rpm shown.
Table 4 — Fan Rpm at Motor Pulley Settings*
MOTOR PULLEY TURNS OPEN
1 1 1 ⁄ 2
2
1025 990 960
1115 1080 1045
1385 1350 1315
1490 1445 1400
CAPACITOR
(551B036, 048
SINGLE-PHASE
UNITS ONLY)
Fig. 26 — Belt Drive Motor Mounting
Fig. 27 — Evaporator-Fan Pulley Adjustment
3. Tighten motor mounting nuts.
4. Adjust bolt and tighten nut to secure motor in fixed
position.
2 1 ⁄ 3 3 1 ⁄
2 2
925 890 860
1015 980 945
1275 1240 1205
1350 1305 1260
—20—
4 4 1 ⁄ 5
2
825 795 760
910 875 840
1165 1130 1095
1210 1165 1120
5 1 ⁄ 6
2
— —
— —
1050 1020
— —