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912SD: Installation, Start-up, Operating and Service and Maintenance Instructions
The electronic air cleaner terminal EAC-1 is energized with 115
vac when the blower motor BLWM is operating. When the
thermostat is satisfied, the R-to-G-and-Y circuits are opened. The
outdoor unit will stop, and the furnace blower motor BLWM will
continue operating on the COOL speed for an additional 90 sec.
3. Continuous Blower Mode
When the R-to-G circuit is closed by the thermostat, the blower
motor BLWM will operate on continuous-blower speed (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 sec), ignition (7 sec), and
blower-ON delay (25 sec), 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 high-cooling", the blower motor
BLWM will operate at COOL speed. When the thermostat is
satisfied, the blower motor BLWM will operate an additional 90 sec
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 sec, if no other function
requires blower motor BLWM operation.
4. Heat pump
See
Fig. 37
and
Fig. 39
for thermostat connections. When installed
with a heat pump, the furnace control automatically changes the
timing sequence to avoid long blower off times during demand
defrost cycles. When the R-to-W-and-Y or R-to-W-and-Y-and-G
circuits are energized the furnace control CPU will continue to 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 sec 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 sec delay. If the
R-to-W-and-Y-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 signals disappear, leaving the G signal,
the blower motor BLWM will continue running the blower motor at
HEAT speed after the selected blower-OFF delay period is
completed.
Component Self-Test
Refer to page 56 for instructions.
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
Fig. 71 – Service Label Information
63
A190035
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