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Adjust Tap
Airflow amounts may be increased or decreased by 10% by
moving the ADJUST jumper plug (see Figure 54) from the
NORM position to the (+) or (-) position. Changes to the
ADJUST tap will affect both cooling and heating airflows.
The TEST position on the ADJUST tap is not used.
Continuous Blower Operation
The comfort level of the living space can be enhanced when
using this feature by allowing continuous circulation of air
between calls for cooling or heating. The circulation of air
occurs at half the full cooling airflow rate.
To engage the continuous blower operation, place the
fan switch on the thermostat into the ON position. A call
for fan from the thermostat closes R to G on the ignition
control board. The control waits for a 1 second thermostat
debounce delay before responding to the call for fan by
ramping the circulating blower up to 50% of the cooling
speed. When the call for continuous fan is satisfied, the
control immediately ramps down the circulating blower.
ADJUST, HEAT, and COOL Taps
on Integrated Ignition/Blower
Control Board
Page 40 of 58
Figure 54
Sequence of Operation
Heating
On a call for heat from the room thermostat, the control board
performs a 1 second self check. Upon confirmation that the
pressure switch contacts are in an open position, the control
energizes the combustion blower on high speed. The control
then checks for adequate combustion air by making sure
the low-fire pressure switch contacts are closed.
The igniter energizes and is allowed to warm up for 20
seconds before the gas valve energizes on 1
burners ignite. 45 seconds after the control confirms ignition
has occurred, the control drops the combustion blower to
low speed.
The circulating blower ramps up to 50% of 1
speed and operates at that speed for one minute (including
ramp up time), then at 75% of 1
additional minute. After that, the circulating blower operates
at full 1
stage heat speed until either the heat call is satisfied
st
or the thermostat initiates a call for 2
for 2
stage heat, the control energizes the circulating air
nd
blower on full CFM 2
If the automatic heat staging option is being used the
furnace does not switch to 2
call from the thermostat but instead operates at 1
for the duration of the selected time before automatically
switching to 2
stage heat.
nd
When the call for heat is satisfied, the gas valve and
combustion air blower shut down. The control board shuts
off the gas valve and runs the combustion blower for an
additional 15 seconds. The circulating air blower continues
to run for 2 minutes at 82% of the selected heating speed
(low fire or high fire) before ramping down.
In the event the unit loses ignition, the control will attempt to
recycle up to five times before it goes into a 1 hour lockout.
Lockout may be manually reset by removing power from the
control for more than 1 second or removing the thermostat
call for heat for more than 3 seconds.
If during a heating cycle the limit control senses an abnormally
high temperature and opens, the control board de-energizes
the gas valve and the combustion blower while the circulating
blower ramps up to 2
blower remains energized until the limits are closed.
Fan On
When the thermostat is set for continuous fan operation
and there is no demand for heating or cooling, a call for
fan closes
the R to G circuit and the circulating blower motor runs at 50%
of the selected cooling CFM until switched off. When the call for fan is
turned OFF, the control de-energizes the circulating blower.
Issue 1621
stage heat speed for an
st
stage heat. On a call
nd
stage heat.
nd
stage heat in response to a
nd
stage heat speed. The circulating
nd
stage and
st
stage heat
st
stage heat
st
507052-04
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