035-20499-001 Rev. B (1004)
Unitary Products Group
21
CFM Board - Delay Taps Selection
The set of jumper pins on the CFM board labeled "DELAY" are used to
set the delay profiles for the furnace. These can be chosen so as to
maximize the comfort and sound levels for various regions of the coun-
try.
Tap A
is the default profile. It provides a 30-second ramp-up from zero
airflow to full capacity and a 30-second ramp-down from full capacity
back to zero airflow. Whenever there is a change in airflow mode, such
as from low heat to high heat, the motor will take 30 seconds to ramp
from one speed to the other.
Tap B
is the humid profile. This profile is best-suited for installations
where the humidity is frequently very high during cooling season, such
as in the southern part of the country. On a call for cooling, the blower
will ramp up to 50% of full capacity and will stay there for two minutes,
then will ramp up to 82% of full capacity and will stay there for five min-
utes, and then will ramp up to full capacity, where it will stay until the
wall thermostat is satisfied. In every case, it will take the motor 30 sec-
onds to ramp from one speed to another.
Tap C
is the dry profile. This profile is best suited to parts of the country
where excessive humidity is not generally a problem, where the sum-
mer months are usually dry. On a call for cooling the motor will ramp up
to full capacity and will stay there until the thermostat is satisfied. At the
end of the cooling cycle, the blower will ramp down to 50% of full capac-
ity where it will stay for 60 seconds. Then it will ramp down to zero. In
every case, it will take the motor 30 seconds to ramp from one speed to
another.
Tap D
is the normal profile, best suited for most of the country, where
neither excessive humidity nor extremely dry conditions are the norm.
On a call for cooling, the motor will ramp up to 63% of full capacity and
will stay there for 90 seconds, then will ramp up to full capacity. At the
end of the cooling cycle, the motor will ramp down to 63% of full capac-
ity and will stay there for 30 seconds, then will ramp down to zero. In
every case, it will take the motor 30 seconds to ramp from one speed to
another.
Continuous Blower Operation
The blower will run continuously whenever the wall thermostat fan
switch is in the "ON" position. The furnace blower will run at the speed
selected on the "FAN SPEED" jumpers on the main control board (HI
COOL, LO COOL, HI HEAT or LO HEAT). When the jumper is in the
"VS G" position, the blower will run at 50% of the high cool speed.
Intermittent Blower Cooling
On cooling/ heating thermostats with a fan switch, when the fan switch
is set in the auto position and the thermostat calls for cooling, a circuit is
completed between the R, Y and G terminals. The motor is energized
through the Y1 cool terminal and runs on the speed selected on the
COOL tap of the CFM Timer board. The fan off setting is fixed at 60
seconds for SEER enhancement. The control board can accommodate
two-stage cooling. When a two-stage cool thermostat is connected to
the Y1 and Y2 terminals on the board, the blower will operate on LOW
COOL speed when Y1 is energized and on HI COOL speed when Y1
and Y2 are energized.
Intermittent Blower Heating
On cooling/ heating thermostats with a fan switch, when the fan switch
is set in the auto position and the thermostat calls for heating, a circuit is
completed between the R and W terminals. The indoor fan motor is
energized through the W1 heat terminal and runs on the speed selected
on the HEAT tap of the CFM Timer board.
Humidistat
When a humidistat is installed in the system, the “Humidistat Installed?”
jumper on the CFM board should be moved to the “YES” position. The
cooling CFM will then be reduced by 15% whenever the humidistat indi-
cates high humidity.
FIGURE 27:
CFM / Timer Board
CFM
TIMER
BOARD
HEA
T
PUMP
HUMIDIST
AT
