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Configuring the Fixed Speed Blower
The fixed speed blower assembly has been designed to
give the installer maximum flexibility for optimizing system
performance, efficiency, and comfort. It is equipped with
a microprocessor-controlled motor when coupled with a
fixed speed motor control board delivers constant torque
to optimize airflow in a variety of conditions and system
configurations. Because the blower can be configured in
many ways, it is important to read and follow all instructions
carefully.
Upon initial start up, the fixed speed blower must be
checked so that the factory settings match the unit with
the system, climatic conditions, and other system options.
With the blower installed and configured properly, the
furnace will change speed in response to changes in
system variables such as Heat/Cool setting, Fan Auto/
On, or 2 Stage furnace High/Low Heat. The fixed speed
blower is configured by setting the 8 switches for heating
and cooling operation located on the blower control board.
Use pins 1 to 4 to set the blower speed for heating and
pins 5 to 8 to set the speed for cooling. To determine the
appropriate switch settings for your installation, see Tables
9-13 (pages 24-28) for heating or Table 8 (page 24) for
cooling. See Figure 10 (page 31) for switch locations.
NOTE: For change in blower speed selection to take
effect, system power must be cycled off then restored
after 10 seconds.
Selecting Cooling Airflow
(Switches # 5, 6, 7, & 8)
The COOLING airflow is selected by setting switches #
5, 6, 7, & 8 on the motor control board (Figure 10, Page
31). Table 8 (page 24) lists the recommended airflow
values (CFM) and switch settings for each nominal cooling
system capacity. All airflows for other modes of operation
are determined by these basic settings. For maximum
capacity, generally, a selection near the middle or top of
the CFM range for that nominal capacity is used. Factory
settings are displayed in BOLD ITALICS
Selecting Heating Airflow
(Switches # 1, 2, 3, & 4)
The HEATING airflow is selected by setting switches #
1, 2, 3, & 4 on the motor control board (Figure 10, Page
31). Tables 9-13, (pages 24-28) lists the recommended
airflow values (CFM) and switch settings for each heat
exchanger capacity. All airflows are determined by these
basic settings. For most applications the factory heat
setting will operate at a nominal rise based on the furnace's
nominal efficiency and firing input. Follow across the table
row to find the switch setting and nominal air-flow. Verify
the selected rise is within the specification shown on the
furnace rating label or Tables 9-13.
Dehumidification Options
The fixed speed motor control board has a DEHUM
connection that allows the system to increase the amount
of humidity that is removed from the circulating air. This
is accomplished by reducing the CFM and allowing the
cooling coil to become colder. This function is only available
when there is a call for cooling. There are many ways this
function can be electrically wired.
When 24VAC is present at the DEHUM terminal of the
blower control board the airflow requirements will be
reduced to approximately 75% of the nominal airflow
requirements. If the humidity level of the conditioned space
decreases during the cycle and the humidistat opens, the
airflow will be restored to 100% of the selected value.
• If the room thermostat incorporates a humidity sensor
and DEHUM output, connect the DEHUM on the
thermostat to the DEHUM terminal on the motor control
board. See Figure 10 (page 31).
• If using a separate humidistat, connect the DEHUM & R
terminals on the humidistat to the DEHUM & R terminals
on the motor control board. In this option, the DEHUM
output of the humidistat must be set to be normally open
and closed when there is a call for humidification.
If a humidistat is not available, it is an acceptable option
to directly jumper the R & DEHUM on the blower control
board. NOTE: This option will always operate the blower
at 75% the rated airflow for the first 10 minutes of every
cooling cycle no matter what the humidity level of the
home is. See Figure 10.
CAUTION:
To avoid personal injury or property damage,
make sure the motor leads do not come into
contact with any uninsulated metal components
of the unit.
O p t i o n a l F u r n a c e C o n t r o l B o a r d
Connections
Electronic Air Cleaner
The furnace control board provides output terminals
for an optional electronic air cleaner (EAC) that can be
installed in the return air duct of your system. The EAC
output is energized any time the HEAT or COOL blower
speed is energized. Control ratings are 1.0 Amp. @ 240
VAC. Output connections are made via board terminals
labeled EAC and NEUTRAL.
Humidifier
The furnace control board provides output terminals for
an optional humidifier (HUM) that can be installed on
your system. The HUM output is energized any time the
furnace inducer motor is energized. Control ratings are
1.0 Amp. @ 240 VAC. Output connections are made via
board terminals labeled HUM and NEUTRAL.
Check all factory wiring to the units wiring diagram (Figure
12, page 32). Inspect the factory wiring connections to
be sure none loosened during shipping or installation.
11
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