International comfort products F9MXE0401410A, Service And Technical Support Manual

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SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXE
Specifications subject to change without notice.
440 04 4311 08 27
applies to operation with a humidity sensing thermostat.
The exceptions are listed below:
a. When the R
− to − G − and − Y1 circuit is closed and there
is a demand for dehumidification, the furnace blower
motor BLWM will continue running at low − cool speed
(same speed as FAN).
b. When the R − to − G − and − Y/Y2 circuit is closed and there
is a demand for dehumidification, the furnace blower
motor BLWM will drop the blower speed from COOL to
HEAT for a maximum of 10 minutes before reverting
back to COOL speed. If there is still a demand for
dehumidification 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 and there is a
demand for dehumidification, the cooling blower − OFF
delay is decreased from 90 seconds to 5 seconds.
4. Continuous Blower Mode
When the R − to − G circuit is closed by the thermostat, the
blower motor BLWM will operate on continuous − blower
speed (same speed as FAN). Terminal EAC 1 AMP 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 (25 seconds), 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 heat − off
delay period before reverting to continuous − blower
speed. When the thermostat “calls for low − cooling,” the
blower motor BLWM will remain operating at 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 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.
5. Heat pump
(See Figure 17 − Figure 23 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 − 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.
See Component Self Test
Refer to page 15 for instructions.