Sequence Of Operation; Wiring Diagrams; Troubleshooting - Bryant 140/E series Installation, Start-Up, Operating And Service And Maintenance Instructions

the furnace blower motor BLWM on COOL speed.
The electronic air cleaner terminal EAC- -1 is energized
with 115 vac whenever the blower motor BLWM is oper-
ating.
When the thermostat is satisfied, the R- -to- -G- -and- -Y1 or
R- -to- -G- -and- -Y1 and Y2 circuits are opened. The out-
door unit stops, and the furnace blower BLWM and elec-
tronic air cleaner terminal EAC- -1 will remain energized
for an additional 90 seconds. Jumper Y1 to DHUM to re-
duce the cooling off- -delay to 5 seconds. (See Fig. 24.)
3. Thermidistat Mode
(See Fig. 26- -29 for Thermidistat connections.)
The dehumidification output, DHUM on the Thermidistat
should be connected to the furnace control thermostat ter-
minal DHUM. When there is a dehumidify demand, the
DHUM input is activated, which means 24 vac signal is
removed from the DHUM input terminal. In other words,
the DHUM input logic is reversed. The DHUM input is
turned ON when no dehumidify demand exists. Once 24
vac is detected by the furnace control on the DHUM input,
the furnace control operates in Thermidistat mode. If the
DHUM input is low for more than 48 hours, the furnace
control reverts back to non- -Thermidistat mode.
The cooling operation described in item 2. above also ap-
plies to operation with a Thermidistat. 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 mo-
tor 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 dehu-
midification after 20 minutes, the furnace control CPU
will drop the blower speed back to HEAT speed. This al-
ternating 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 de-
mand 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 (can be adjusted to FAN, HEAT, or COOL speed) at
the thermostat. 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 (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 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 satis-
fied, the blower motor BLWM will operate an additional
90 seconds on low- -cool speed (same speed as FAN) be-
fore reverting back 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 oper-
ate an additional 90 seconds on COOL speed before re-
verting 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 fact-
ory 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. Repeat-
ing the procedure will shift the continuous- -blower speed
from COOL 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.
5. Heat pump
(See Fig. 28- - 31 for thermostat connections.) When in-
stalled 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 ener-
gized 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 sig-
nal 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.

Wiring Diagrams

Refer to Fig. 54 for wiring diagram.

Troubleshooting

Refer to the service label (See Fig. 50). The Troubleshooting
Guide (See Fig. 55) can be a useful tool in isolating furnace
operation problems. Beginning with the word "Start," answer
each question and follow the appropriate arrow to the next item.
The Guide will help to identify the problem or failed component.
After replacing any component, verify correct operation
sequence.
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