6
surfaces are signs of improper belt tension and/or belt
slippage. Pulley replacement may be necessary.
Changing Fan Speed
1. Shut off the main unit power supply, and use the ap-
proved Lockout/Tagout procedures.
2. Loosen the belt by loosening the motor adjustment
bolts as described in the Belt Adjustment section
above.
3. Loosen the movable pulley flange setscrew. (See Fig.
6.)
4. Screw the movable flange toward fixed flange to in-
crease speed and away from fixed flange to decrease
speed. Increasing fan speed increases load on the mo-
tor. Do not exceed maximum speed specified in the
Product Data or motor amperage listed on the unit rat-
ing plate..
5. Set the movable flange at the nearest keyway or flat
of the pulley hub and tighten the setscrew to torque of
72 ± 5 in−lbs (8.14 ± 0.56 Nm).
Aligning the Fan and Motor Pulleys
1. Loosen the fan pulley setscrews.
2. Slide the fan pulley along the fan shaft. Make angular
alignment by loosening the motor from its mounting.
See Fig. 7.
3. Tighten the fan pulley setscrews and motor mounting
bolts to torque specifications.
4. Recheck the belt tension. See Fig. 6.
C07075
Fig. 7 − Supply−Fan Pulley Adjustment
Bearings
This fan system uses bearings featuring concentric split
locking collars. The collars are tightened through a cap
screw bridging the split portion of the collar. The cap
screw has a Torx T25 socket head. To tighten the locking
collar: Hold the locking collar tightly against the inner
race of the bearing and torque the cap screw to 65−70
in−lb (7.4−7.9 Nm). See Fig. 8.
LOCKING COLLAR
T-25 TORX SOCKET
HEAD CAP SCREW
C11505
Fig. 8 − Tightening Locking Collar
STAGED AIR VOLUME (SAV) CONTROL:
2−SPEED FAN WITH VARIABLE
FREQUENCY DRIVE (VFD)
Staged Air Volume (SAV) Indoor Fan Speed
System
NOTE: The SAV option is not available on units with
Humidi−MiZer adaptive humidification system.
The SAV system utilizes a Fan Speed control board and
Variable Frequency Drive (VFD) to automatically adjust
the indoor fan motor speed in sequence with the unit’s
ventilation, cooling and heating operation. Conforming to
ASHRAE 90.1 2010 Standard Section 6.4.3.10.b, during
the first stage of cooling operation the SAV system will
adjust the fan motor to provide two- thirds (2/3) of the
design airflow rate for the unit. When the call for the
second stage of cooling is required, the SAV system will
allow the design airflow rate for the unit established
(100%). During the heating mode, the SAV system will
allow total design airflow rate (100%) operation. During
ventilation mode, the SAV system will operate the fan
motor at 2/3 speed.
Identifying Factory Option
This supplement only applies to units that meet the
criteria detailed in Table 1. If the unit does not meet that
criteria, discard this document.
Table 1 – Model−Size / VFD Option Indicator
Model / Sizes
Position in
Model Number
VDP
FIOP Indicator
50TC 17 − 30 17 G, J
See Appendix I for the Model Number Nomenclature
breakdown.
Unit Installation with SAV Option
50HC Rooftop—Refer to the base unit installation
instructions for standard required operating and service
clearances.
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