157
BELT INSTALLATION AND TENSIONING
1. Turn off unit power.
2. Adjust motor plate so belts can be installed without
stretching over the grooves of the pulley. (Forcing the
belts can result in uneven belt stretching and a mis-
matched set of belts.) See Fig. 53.
3. Before tensioning the belts, equalize belt slack so that it is
on the same side of the belt for all belts. Failure to do so
may result in uneven belt stretching.
4. Tighten belts using the motor plate adjusting bolts.
5. Adjust until proper belt tension (
1
/
2
-in. [13 mm] deflec-
tion with one finger centered between pulleys) is
obtained. Be sure to adjust both adjusting bolts the same
number of turns. Excessive belt tension shortens belt life
and may cause bearing and shaft damage.
NOTE: Check the tension at least twice during the first
day of operation, as there is normally a rapid decrease in
tension until the belts have run in. Check tension periodi-
cally thereafter and keep it at the recommended tension.
PULLEY ALIGNMENT — For proper belt life, the motor
and fan pulleys must be properly aligned. To check, first turn
off unit power. Place a straightedge against the motor and fan
pulleys. See Fig. 54. If the pulleys are properly aligned, the
straightedge should be parallel to the belts.
If they are not parallel, check that the motor shaft and fan
shaft are parallel. If they are not, adjust the motor plate adjust-
ing bolts until they are.
After verifying that the shafts are parallel, loosen the set-
screws on the motor pulley. Move pulley on the shaft until the
pulleys are parallel. To move the sheave on the shaft, loosen the
belts. If necessary, blower sheave can also be moved on the
shaft.
INSTALLING REPLACEMENT MOTOR PULLEY — To
install a field-supplied replacement pulley:
1. Turn off unit power.
2. Loosen belts using motor adjusting bolts until belts can
be removed without stretching them over the grooves of
the pulley.
3. Remove belts.
4. Loosen setscrews on motor pulley.
5. Slide pulley off motor shaft. Make sure setscrews on new
pulley are loose.
6. Slide new pulley onto fan shaft and align it with the fan
pulley as described in Pulley Alignment section above.
7. Tighten setscrews.
8. Install belts and tension properly as described in Pulley
Alignment section above.
CONDENSER FAN ADJUSTMENT (Metal Fans)
1. Turn off unit power.
2. Remove fan guard and loosen fan hub setscrew.
3. See Fig. 55 and adjust fan height using a straight edge
laid across the fan deck.
4. Tighten setscrew to 12.5 to 13.75 ft-lb and replace rubber
hubcap to prevent hub from rusting to the motor shaft.
Fill hub recess with Permagum if hub has no rubber hub-
cap.
5. Replace fan guard.
CONDENSER FAN ADJUSTMENT (Plastic Fans) —
Each fan is supported by a formed wire mount bolted to a fan
deck and covered with a wire guard. The exposed end of the
fan motor shaft is protected from weather by grease. If the fan
motor must be removed for service or replacement, be sure to
regrease fan shaft and reinstall fan cover, retaining clips, and
fan guard. For proper performance, the fans should be posi-
tioned as shown in Fig. 56. Tighten setscrews to 14 1 ft-lb
(18 1.3 N-m).
Check for proper rotation of the fan(s) once reinstalled
(counterclockwise viewed from above). If necessary to reverse,
switch leads at contactor(s) in control box.
AIR PRESSURE TRANSDUCER FIELD ADJUST-
MENT — All transducers have been factory calibrated and
should not require field adjustment. If field adjustment is
necessary, follow the instructions below. To re-calibrate a
transducer:
1. Shut the unit power off.
2. Take the wiring and pressure tubing off the transducer.
Take the transducer out of the unit.
3. Connect a 24-vdc power supply to transducer terminals
EXC(+) and COM(–). See Fig. 57.
4. Using a digital multimeter measure the current between
terminals EXC(+) and OUT.
5. With both pressure ports open to atmosphere adjust the
Zero (Z) screw potentiometer on the transducer and read
the multimeter until the desired current output at 0 in. wg
pressure is obtained (see Fig. 57).
6. Reinstall the transducer in the unit.
7. Restore power to the unit.
IMPORTANT: When installing or replacing belts,
always use a complete set of new, matched belts to pre-
vent potential vibration problems. Mixing belts often
results in premature breakage of the new belts.
Fig. 53 — Motor Plate Adjustment
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