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As the pitch diameter is changed by adjusting the position of the
movable flange, the centerline on this pulley shifts laterally (along
the motor shaft). This creates a requirement for a realignment of
the pulleys after any adjustment of the movable flange. Reset the
belt tension after each realignment.
Check the condition of the motor pulley for signs of wear. Glazing
of the belt contact surfaces and erosion on these surfaces are signs
of improper belt tension and/or belt slippage. Replace pulley if
necessary.
FAN PULLEY
MOTOR AND
FANSHAFTS
MUST BE
PARALLEL
MOTOR PULLEY
Fig. 7 — Supply-Fan Pulley Adjustment
Changing the Fan Speed
1. Shut off unit power supply. Use proper lockout/tag-out
procedures.
2.
Loosen belt by loosening fan motor mounting nuts. See
Fig. 7.
3.
Loosen movable pulley flange setscrew. See Fig. 7.
4.
Screw movable flange toward fixed flange to increase speed
and away from fixed flange to decrease speed. Increasing fan
speed increases load on motor. Do not exceed the maximum
specified speed.
5.
Set movable flange at nearest keyway of pulley hub. Tighten
setscrew and torque to 65 to 70 in.-lb (7.4 to 7.9 Nm).
Aligning Fan and Motor Pulleys
1.
Loosen fan pulley setscrews.
2.
Slide fan pulley along fan shaft. Make angular alignment by
loosening motor mounting plate front and rear bolts.
3.
Tighten fan pulley setscrews and motor mounting bolts and
torque to 65 to 70 in.-lb (7.4 to 7.9 Nm).
4.
Recheck belt tension.
Bearings
The fan system uses bearings featuring concentric split locking
collars. A Torx
T25 socket head cap screw is used to tighten the
1
locking collars. Tighten the locking collar by holding it firmly
against the inner race of the bearing and tightening the socket head
cap screw. Torque the socket head cap screw 55 to 60 in.-lb (6.2 to
6.8 Nm). See Fig. 8.
1. Torx is a registered trademark of Acument Intellectual Properties
LLC.
MOVABLE
FLANGE
STRAIGHT EDGE
MUST BE PARALLEL
WITH BELT
SETSCREWS
FIXED FLANGE
SINGLE - GROOVE
Fig. 8 — Tightening Locking Collar
Motor
Always replace the external-tooth lock washer (star washer) under
the motor mounting base; this is part of the motor grounding sys-
tem. Ensure the teeth on the lock washer are in contact with the
motor's painted base. Tighten motor mounting bolts and torque to
120 ± 12 in.- lb (14 ± 1.4 Nm).
Change fan wheel speed by changing the fan pulley (larger pitch
diameter to reduce wheel speed, smaller pitch diameter to increase
wheel speed) or select a new system (both pulleys and matching
belt). The horsepower rating of the belt is primarily dictated by the
pitch diameter of the smaller pulley in the drive system (typically
the motor pulley in these units). Do not install a replacement mo-
tor pulley with a smaller pitch diameter than was provided on the
original factory pulley.
Before changing pulleys to increase fan wheel speed, check the
fan performance at the target speed and airflow rate to determine
new motor loading (bhp). Use the fan performance tables or use
the Packaged Rooftop Builder software program. Confirm that the
motor in this unit is capable of operating at the new operating
condition. Fan shaft loading increases dramatically as wheel speed
is increased.
To reduce vibration, replace the motor's adjustable pitch pulley
with a fixed pitch pulley (after the final airflow balance adjust-
ment). This will reduce the amount of vibration generated by the
motor/belt-drive system.
STAGED AIR VOLUME (SAV) CONTROL: 2-
SPEED FAN WITH VARIABLE FREQUENCY
DRIVE (VFD)
Staged Air Volume (SAV) Indoor Fan Speed
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 66% of the de-
sign 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 mo-
tor at 66% speed.
Identifying Factory Option
This section only applies to units that meet the criteria detailed in
Table 1. See Appendix A for the model number nomenclature
breakdown.
5
LOCKING COLLAR
T--- 25 TORX SOCKET
HEAD CAP SCREW
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Troubleshooting
