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WARNING:
!
To avoid electric shock, personal in-
jury, or death, disconnect the electric
power before performing any mainte-
nance.
Configuring the Blower
The variable speed blower kit is equipped with
a microprocessor-controlled variable speed
motor that is pre-programmed to deliver opti-
mum airflow in a variety of conditions and
system configurations. Before operation, the
variable speed blower kit must be configured
to match the unit with the system, system
options, and climatic conditions. With the vari-
able speed blower kit installed and configured
properly, the furnace will respond directly to
gradually change speed in response to changes
in system variables such as the thermostat
settings, duct static, filter, etc. The variable
speed blower kit is configured by setting the 7
switches located on the motor control board as
described below.
!
IMPORTANT:
The variable speed blower kit has been
designed to give the installer maxi-
mum flexibility to optimize system per-
formance, efficiency, and comfort.
Because there are so many ways to
configure the kit it is important to read
and follow these instructions carefully.
Selecting Heat Airflow
The heating airflow is selected by setting
switches 5, 6 , and 7. Refer to Table 1a and
select a nominal rise based on the furnace
nominal efficiency and input. Follow the table
column up to find the switch setting and nominal
air-flow. Be sure that the selected rise is within
the specification of the furnace as shown on the
furnace rating label. For single stage cooling,
reference the CFM in the high column.
Selecting The Cooling/Heat Pump
Airflow
In order to select the appropriate airflow for AC
and HP operation the nominal system capacity
must be known. The nominal system capacity
is ALWAYS the nominal capacity of the outdoor
unit. In some cases the nominal system capac-
ity is not the same as the nominal capacity of the
indoor coil.
The cooling/heat pump airflow is selected by
setting switches 1 through 4 on the motor control
board located in the blower control panel. All
airflows for other modes of operation (except
gas heat) are determined by this setting. Table
1 shows the airflow values versus the airflow
selector switch settings, and the range of airflow
settings recommended for each nominal sys-
tem capacity.
NOTE: The CFM values listed on Table 2 are
not dependent on duct static pressure. The
motor automatically compensates for
changes in duct static pressure (within the
limits of the motor).
For maximum capacity and energy efficiency,
generally, a selection at or near the top of the
CFM range for that nominal capacity is best. For
maximum dehumidification, select an airflow
near the middle or bottom of the CFM range for
that nominal capacity.
NOTE: If coil icing is observed, the cooling/
heat pump airflow selected may be too low.
Double-check to be sure the setting se-
lected is within the range shown in Table 1.
Also check to be sure the system is properly
charged (see outdoor unit installation in-
structions). If icing continues to occur,
raise the selected airflow one or two steps.
Verifying and Adjusting
Temperature Rise
Verify that the temperature rise through the
furnace is within the range specified on the
furnace rating plate. Temperature rises outside
the specified range could result in premature
heat exchanger failure.
Place thermometers in the return and supply air
stream as close to the furnace as possible. The
thermometer on the supply air side must be
shielded from direct radiation from the heat
exchanger to avoid false readings. Adjust all
registers and duct dampers to the desired
position and run the furnace for fifteen minutes
before taking any temperature readings. The
temperature rise is the difference between the
supply and return air temperatures.
35
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