Changing The Fan Speed; Aligning Blower And Motor Pulleys; Identifying Factory Option; Unit Installation With Sav Option - Carrier 50HC Series Service And Maintenance Instructions

around the fixed flange side that increases or reduces the
pitch diameter of this driver pulley. (See Fig. 8.)
FAN PULLEY
MOTOR AND
FANSHAFTS
MUST BE
PARALLEL
MOTOR PULLEY
Fig. 8 - - Supply- - Fan Pulley Adjustment
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.
Inspect 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 wear is excessive.

Changing the Fan Speed:

1. Shut off unit power supply. Use proper lockout/tagout
procedures.
2. Loosen belt by loosening fan motor mounting nuts.
(See Fig. 6.)
3. Loosen movable pulley flange setscrew. (See Fig. 8.)
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- - 70 in- - lb (7.4 to 7.9
Nm).

Aligning Blower and Motor Pulleys:

1. Loosen blower pulley setscrews.
2. Slide blower pulley along blower shaft. Make angular
alignment by loosening motor mounting plate front
and rear bolts.
3. Tighten blower pulley setscrews and motor mounting
bolts. Torque bolts to 65- - 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 T- - 25 socket head cap screw is
used to tighten the locking collars. Tighten the locking
collar by holding it tightly against the inner race of the
bearing. Tighten the socket head cap screw. Torque cap
screw to 65- - 70 in- - lb (7.4- - 7.9 Nm). See Fig. 9. Check the
MOVABLE
FLANGE
STRAIGHT EDGE
MUST BE PARALLEL
WITH BELT
SETSCREWS
FIXED FLANGE
SINGLE - GROOVE
C07075
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.
Fig. 9 - - Tightening Locking Collar
STAGED AIR VOLUME CONTROL - -
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 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 3. If the unit does not meet that
criteria, discard this document.
Table 3 – Model- - Size / VFD Option Indicator
Model / Sizes
50HC / 08--- 28
NOTE: See Fig. 57 for an example of Model Number
Nomenclature.

Unit Installation with SAV Option

50HC Rooftop — Refer to the base unit installation
instructions for standard required operating and service
clearances.
7
LOCKING COLLAR
T--- 25 TORX SOCKET
HEAD CAP SCREW
Position in VFD FIOP
Model Number Indicator
17 G, J
C11505