after 20 minutes, the furnace control CPU will drop the
blower speed back to HEAT speed. This alternating 10-
minute cycle will continue as long as there is a call for
cooling.
c. When the ″call for cooling″ is satisfied while there is a
demand for dehumidification, the cooling blower-off delay
is decreased from 90 seconds to 5 seconds.
CONTINUOUS BLOWER MODE
When the R to G circuit is closed by the thermostat, the blower
motor BLWM will operate on continuous-blower speed (can
be adjusted to FAN, HEAT, or COOL speed) at the thermo-
stat. Factory default is FAN speed. Terminal EAC-1 is
energized as long as the blower motor BLWM is energized.
During a call for heat, the blower BLWM will stop during
igniter warm-up (17 seconds), ignition (7 seconds), and
blower-ON delay (66 or 45 seconds for 040 through 120 sizes
or for 140 size), allowing the furnace heat exchangers to heat
up more quickly, then restarts at the end of the blower-ON
delay period at HEAT speed.
In heating, the furnace control CPU will hold the blower
motor BLWM at HEAT speed during the selected blower-OFF
delay period before reverting to continuous-blower speed.
When the thermostat ″calls for low-cooling″, the blower motor
BLWM will switch to operate at low-cool speed (same speed
as FAN). When the thermostat is satisfied, the blower motor
BLWM will operate an additional 90 seconds on low-cool
speed (same speed as FAN) before reverting back to
continuous-blower speed.
When the thermostat ″calls for high-cooling″, the blower
motor BLWM will operate at COOL speed. When the ther-
mostat is satisfied, the blower motor BLWM will operate an
additional 90 seconds on COOL speed before reverting back
to continuous-blower speed.
When the R to G circuit is opened, the blower motor BLWM
will continue operating for an additional 5 seconds, if no other
function requires blower motor BLWM operation.
Continuous Blower Speed Selection from Thermostat -To
select different continuous-blower speeds from the room
thermostat, momentarily turn off the FAN switch or push-
button on the room thermostat for 1-3 seconds after the blower
motor BLWM is operating. The furnace control CPU will shift
the continuous-blower speed from the factory setting of FAN
to HEAT speed. Momentarily turning off the FAN switch
again at the thermostat will shift the continuous-blower speed
from HEAT to COOL. Repeating the procedure will shift the
continuous-blower speed from COOL back to FAN speed.
The selection can be changed as many times as desired and is
stored in the memory to be automatically used following a
power interruption.
HEAT PUMP MODE
(See Fig. 50, 51, 52, and 53 for thermostat
connections.)
When installed with a heat pump, the furnace control auto-
matically changes the blower timing sequence to avoid long
blower off times during demand defrost cycles. When the R to
W-and-Y1 or R to W-and-Y1-and-G circuits are energized the
furnace control CPU will switch to or turn on the blower
motor BLWM at HEAT speed, and begin a heating cycle. The
blower motor BLWM will remain on until the end of the
prepurge period, then shut off for 24 seconds then come back
on at HEAT speed. When the W input signal disappears, the
furnace control begins a normal inducer post-purge period and
the blower remains running at HEAT speed for the selected
blower-OFF delay period then switches to low-cool speed
(same speed as FAN). If the R to W-and-Y1-and-G signals
disappear at the same time, the blower motor BLWM will
remain on for the selected blower-OFF delay period. If the R
to W-and-Y1 signals disappear, leaving the G signal, the
blower motor BLWM will remain on for the selected blower-
OFF delay period then switch to continuous-blower speed.
When the R to W-and-Y/Y2, R to W-and-Y/Y2-and-G, R to
W-and-Y1-and-Y/Y2, or R to W-and-Y1-and-Y/Y2-and-G
circuits are energized the furnace control CPU will switch to
or turn on the blower motor BLWM at HEAT speed, and
begin a heating cycle. The blower motor BLWM will remain
on until the end of the prepurge period, then shut off for 24
seconds then come back on at HEAT speed. When the W input
signal disappears, the furnace control begins a normal inducer
post-purge period and the blower switches to COOL speed
after a 3-second delay. If the R to W-and-Y/Y2-and-G or R to
W-and-Y1-and-Y/Y2-and-G signals disappear at the same
time, the blower motor BLWM will remain on for the selected
blower-OFF delay period. If the R to W-and-Y/Y2 or R to
W-and-Y1-and-Y/Y2 signals disappear, leaving the G signal,
the blower motor BLWM will remain on for the selected
blower-OFF delay period then switch to continuous-blower
speed.
COMPONENT TEST
NOTE: The furnace control component test allows all compo-
nents to run for a short time; except the gas valve and humidifier
terminal HUM are not energized for safety reasons. The EAC-1
terminal is energized when the blower is energized. This feature
helps diagnose a system problem in case of a component failure.
The component test feature will not operate if any thermostat
signal is present ant the control and not until all time delays are
completed.
To Begin Component Self-Test:
Blower access panel door switch opens 115-v power to
control. No component operation can occur. Caution must be
taken when manually closing this switch for service purposes.
Failure to follow this warning could result in electrical shock,
personal injury, or death.
1. Remove blower access door.
2. Disconnect the thermostat R lead from furnace control.
3. Manually close blower door switch.
4. For approximately 2 sec, short (jumper) the C
OM-24v terminal
on control to the TEST/TWIN 3/16-inch quick-connect termi-
nal on control until the LED goes off. Remover jumper from
terminals. (See Fig. 31.)
NOTE: If TEST/TWIN and C
OM-24v terminals are jumpered
longer than 2 sec, LED will flash rapidly and ignore component
test request.
Component test sequence is as follows:
a. LED will display previous status code 4 times.
b. Inducer motor starts and continues to run until Step g of
component test sequence.
c. After 7 seconds the hot surface igniter is energized for 15
sec., then off.
d. Blower motor operates on Continuous-FAN speed for 10
sec.
e. Blower motor operates on HEAT speed for 10 sec.
f. Blower motor operates on COOL speed for 10 sec.
g. Inducer motor stops.
39
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