128
Adjustments
RETURN/EXHAUST FAN MOTOR PLATE
Adjust using a 3/4-in. wrench on the adjusting bolts:
1. Loosen holddown bolts. (See Fig. 43).
2. Turn the adjusting bolts to move the motor mounting
plate toward or away from the fan to loosen or tighten the
belts. Make the same number of turns to each bolt.
3. Retighten holddown bolts.
SUPPLY FAN AND POWER EXHAUST MOTOR
PLATE — Adjust using a 15/16-in. wrench on the adjusting
bolts:
1. Loosen holddown bolts. (See Fig. 44.)
2. Turn the adjusting bolts to move the motor mounting
plate toward or away from the fan to loosen or tighten the
belts. Make the same number of turns to each bolt.
3. Retighten holddown bolts.
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.)
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.
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.
With the correct belt tension, belts may slip and squeal mo-
mentarily on start-up. This slippage is normal and disappears
after wheel reaches operating speed. Excessive belt tension
shortens belt life and may cause bearing and shaft damage.
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. 45. 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 (Supply
Fan Only) — 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 (All Units Except
050, 070, 075 Units with High-Capacity Evaporator Coil)
1. Turn off unit power.
2. Remove fan guard and loosen fan hub setscrew.
3. See Fig. 46 and adjust fan height using a straight edge
laid across the fan deck.
4. Tighten setscrew and replace rubber hubcap to prevent
hub from rusting to the motor shaft. Fill hub recess with
Permagum if hub has no rubber hubcap.
5. Replace fan guard.
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.
HOLDDOWN BOLTS
HOLD-
DOWN
BOLTS
Fig. 43 — Return/Exhaust Fan Motor
Plate Adjustment
Fig. 44 — Motor Plate Adjustment