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Variable Speed Features
This furnace is equipped with a variable speed circulation
air blower motor that will deliver a constant airflow within a
wide range of external static pressures. Other features of
this variable speed motor include:
Soft Start - The variable speed motor will slowly
•
ramp up to normal operating speed. This minimiz-
es noise and increases comfort by eliminating the
initial blasts of air encountered with standard mo-
tors.
•
Soft Stop - At the end of a cooling or heating cycle,
the variable speed motor will slowly ramp down af-
ter a short blower "off" delay. If continuous blower
operation has been selected, the variable speed
motor will slowly ramp down until it reaches the air-
flow for that mode.
•
Passive Dehumidification - For situations where
humidity control is a problem, a dehumidification
feature has been built into the variable speed mo-
tor. At the start of each cooling cycle, the variable
speed motor will run at 82% of the rated airflow
for 7.5 minutes. After 7.5 minutes has elapsed, the
motor will increase to 100% of the rated airflow.
•
Active Dehumidification - To achieve additional
dehumidification, clip the jumper located near the
DEHUM terminal on the integrated ignition/ blower
control board and connect a humidity control that
opens on humidity rise to the DEHUM and R ter-
minals. The DEHUM terminal on the control board
must be connected to the normally closed contact
of the humidity control so that the board senses an
open circuit on high humidity. In this setup, the vari-
able speed motor will operate at a 30% reduction in
the normal cooling airflow rate when there is a call
for dehumidification.
Both the passive and active dehumidification methods de-
scribed above can be utilized on the same furnace.
Circulating Airflow Adjustments
Heating Mode - These units are factory set to run at
the middle of the heating rise range as shown on the
unit rating plate. See TABLE 16 for allowable heating
speeds. If higher or lower rise is desired, reposition DIP
switches 3 and 4. To determine what CFM the motor
is delivering at any time, count the number of times
the green LED on the control board flashes. Each flash
signifies 100 CFM; count the flashes and multiply by
100 to determine the actual CFM delivered (for exam-
ple: 10 flashes x 100 = 1000 CFM).
Heat Air Flow
High
Med-High
Med-Low
Low
Cooling Mode - The units are factory set for the high-
est airflow for each model. Adjustments can be made
to the cooling airflow by repositioning DIP switches 5
and 6. To determine what CFM the motor is delivering
at any time, count the number of times the green LED
on the control board flashes. Each flash signifies 100
CFM; count the flashes and multiply by 100 to deter-
mine the actual CFM delivered (for example: 10 flash-
es x 100 = 1000 CFM).
Cool Air Flow
High
Med-High
Med-Low
Low
Adjust Tap - Airflow amounts may be increased or de-
creased by 10% by moving the ADJUST DIP switches
7 and 8 from the NORM position to the (+) or (-) posi-
tion. Changes to the ADJUST tap will affect both cool-
ing and heating airflows. The TEST position (DIP7 and
DIP8 both ON) shall not be used for normal furnace
operation.
Adjust Tap
10%
Normal
-10%
Do Not Use¹
¹ When DIP7 and DIP8 are both on, the blower will not run
Continuous Blower Operation FIGURE 32
The comfort level of the living space can be enhanced
when using this feature by allowing continuous circu-
lation of air between calls for cooling or heating. The
circulation of air occurs at 38% the full cooling airflow
rate.
Page 27
TABLE 8
Heating Mode
DIP3
OFF
ON
OFF
ON
TABLE 9
Cooling Mode
DIP5
DIP6
OFF
OFF
ON
ON
TABLE 10
Adjust Tap
DIP7
DIP8
ON
OFF
OFF
ON
DIP4
ON
OFF
OFF
ON
OFF
ON
OFF
ON
OFF
OFF
ON
ON
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