Table of Contents
Advertisement
5. Install the new belt by gently sliding the belt over
both pulleys and then sliding the motor and plate
away from the fan housing until proper tension is
achieved.
6. Check the alignment of the pulleys, adjust if neces-
sary.
7. Tighten all bolts.
8. Check the tension after a few hours of runtime and
re- - adjust as required.
Adjustable- -Pitch Pulley on Motor
The motor pulley is an adjustable- - pitch type that allows a
servicer to implement changes in the fan wheel speed to
match as- - installed ductwork systems. The pulley consists
of a fixed flange side that faces the motor (secured to the
motor shaft) and a movable flange side that can be rotated
around the fixed flange side that increases or reduces the
pitch diameter of this driver pulley. See Fig. 7.
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. Also 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. Pulley replacement can be necessary.
FAN PULLEY
STRAIGHT EDGE
MUST BE PARALLEL
MOTOR AND
WITH BELT
FANSHAFTS
MUST BE
PARALLEL
MOTOR PULLEY
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 55- - 60
in- - lb (6.2- - 6.8 Nm). See Fig. 8.
MOVABLE
FLANGE
SETSCREWS
FIXED FLANGE
SINGLE - GROOVE
C07075
Fig. 8 - - Tightening Locking Collar
STAGED AIR VOLUME CONTROL (SAV) - -
2 SPEED FAN WITH VARIABLE
FREQUENCY DRIVE (VFD)
Staged Air Volume (SAV) Indoor Fan Speed
System
The Staged Air Volume (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. Per ASHRAE 90.1 2010standard 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
Position in
Model / Sizes
Model Number
48TC / 08--- 30
Unit Installation with SAV Option
Refer to the base unit installation instructions for standard
required operating and service clearances.
NOTICE: The remote VFD keypad is a field- - installed
option. It is not included as part of the factory- - installed
VFD option. See Figs. 9, 10 and 11 for locations of the
Variable Frequency Drive (VFD) as mounted on the
various 48TC models.
7
LOCKING COLLAR
T-25 TORX SOCKET
HEAD CAP SCREW
C11505
VFD FIOP
Indicator
17
G, J
Advertisement
Table of Contents
