441 01 3700 00
Specifications are subject to change without notice.
46
d.
Flame--Proving
-- When the burner flame is proved at
the flame--proving sensor electrode FSE, the furnace
control CPU begins the blower--ON delay period and
continues to hold the gas valve GV open. If the burner
flame is not proved within two seconds, the control
CPU will close the gas valve GV, and the control CPU
will repeat the ignition sequence for up to three more
Trials--For--Ignition before going to Ignition--Lockout.
Lockout will be reset automatically after three hours or
by momentarily interrupting 115 vac power to the fur-
nace, or by interrupting 24 vac power at 24VAC or
COM to the furnace control CPU (not at W, G, R, etc.)
If flame is proved when flame should not be present,
the furnace control CPU will lock out of Gas--Heating
mode and operate the inducer motor IDM until flame
is no longer proved.
e.
Blower--On Delay
-- If the burner flame is proven, the
blower motor is energized on HEAT speed 25 sec after
the gas valve GV is energized.
Simultaneously, the electronic air cleaner terminal
EAC--1 is energized and remains energized as long as
the blower motor BLWM is energized.
f.
Heat--Off Delay
-- When the thermostat is satisfied, the
R--to--W circuit is opened, de--energizing the gas valve
GV, stopping gas flow to the burners, and de--energiz-
ing the 24--v humidifier terminal 24VAC HUM. The
inducer motor IDM will remain energized for a 5--sec-
ond post--purge period. Then turn off the inducer mo-
tor. The blower motor BLWM and air cleaner terminal
EAC 1 will remain energized for 90, 120, 150, or 180
seconds (depending on the HEAT--OFF delay selec-
tion). The furnace control CPU is factory--set for a
120--second Heat--Off Delay.
2.
Cooling mode
The thermostat “calls for cooling”.
a.
Single--Speed Cooling
--
See Fig. 27 for thermostat connections
The thermostat closes the R--to--G--and--Y circuits. The
R--to-- Y circuit starts the outdoor unit, and the R--to--
G--and--Y/Y2 circuits start the furnace blower motor
BLWM on cooling airflow. Cooling airflow is based
on the A/C selection shown in Fig. 47. 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
at cooling airflow for an additional 90 seconds.
Jumper Y/Y2 to DHUM to reduce the cooling off--de-
lay to 5 seconds. (See Fig. 48.)
b.
Single--Stage Thermostat and Two--Speed Cooling
(Adaptive Mode)
--
See Fig. 26 for thermostat connections.
This furnace can operate a two--speed cooling unit
with a single--stage thermostat because the furnace
control CPU includes a programmed adaptive se-
quence of controlled operation, which selects low--
cooling or high--cooling operation. This selection is
based upon the stored history of the length of previous
cooling period of the single--stage thermostat.
NOTE
: The air conditioning relay disable jumper ACRDJ must
be connected to enable the adaptive cooling mode in response to
a call for cooling. (See Fig. 48.) When ACRDJ is in place the
furnace control CPU can turn on the air conditioning relay ACR
to energize the Y/Y2 terminal and switch the outdoor unit to
high--cooling.
The furnace control CPU can start up the cooling unit in either
low-- or high--cooling. If starting up in low--cooling, the furnace
control CPU determines the low--cooling on--time (from 0 to 20
minutes) which is permitted before switching to high--cooling. If
the power is interrupted, the stored history is erased and the
furnace control CPU will select low--cooling for up to 20 minutes
and then energize the air conditioning relay ACR to energize the
Y/Y2 terminal and switch the outdoor unit to high--cooling, as
long as the thermostat continues to call for cooling. Subsequent
selection is based on stored history of the thermostat cycle times.
The wall thermostat “calls for cooling”, closing the
R--to--G--and--Y circuits. The R--to--Y1 circuit starts the outdoor
unit on low--cooling speed, and the R--to--G--and--Y1 circuits
starts the furnace blower motor BLWM at low--cooling airflow
which is the true on--board CF selection as shown in Fig. 47.
If the furnace control CPU switches from low--cooling to
high--cooling, the furnace control CPU will energize the air
conditioning relay ACR. When the air conditioning relay ACR is
energized the R--to--Y1--and--Y2 circuits switch the outdoor unit
to high--cooling speed, and the R--to--G--and--Y1--and--Y/Y2
circuits transition the furnace blower motor BLWM to
high--cooling airflow. High--cooling airflow is based on the A/C
selection shown in Fig. 47.
NOTE
: When transitioning from low--cooling to high--cooling
the outdoor unit compressor will shut down for 1 minute while
the furnace blower motor BLWM transitions to run at
high--cooling airflow.
The electronic air cleaner terminal EAC--1 is energized with 115
vac whenever the blower motor BLWM is operating.
When the thermostat is satisfied, the R--to--G--and--Y circuit are
opened. The outdoor unit stops, and the furnace blower BLWM
and electronic air cleaner terminal EAC--1 will remain energized
for an additional 90 seconds. Jumper Y1 to DHUM to reduce the
cooling off--delay to 5 seconds. (See Fig. 48.)
c. Two--Stage Thermostat and Two--Speed Cooling
See Fig. 27 for thermostat connections
NOTE
: The air conditioning relay disable jumper ACRDJ must
be disconnected to allow thermostat control of the outdoor unit
staging. (See Fig. 48.)
The thermostat closes the R--to--G--and--Y1 circuits for
low--cooling or closes the R--to--G--and--Y1--and--Y2 circuits for
high--cooling. The R--to--Y1 circuit starts the outdoor unit on
low--cooling speed, and the R--to--G--and--Y1 circuit starts the
furnace blower motor BLWM at low--cooling airflow which is the
true on--board CF selection as shown in Table 4 and Fig. 47. The
R--to--Y1--and--Y2 circuits start the outdoor unit on high--cooling
speed, and the R--to-- G--and--Y/Y2 circuits start the furnace
blower motor BLWM at high--cooling airflow. High--cooling
airflow is based on the A/C (air conditioning) selection shown in
Fig. 47.
The electronic air cleaner terminal EAC--1 is energized with 115
vac whenever the blower motor BLWM is operating.
When the thermostat is satisfied, the R--to--G--and--Y1 or R--to--
G--and--Y1--and--Y2 circuits are opened. The outdoor unit stops,
and the furnace blower BLWM and electronic air cleaner terminal
EAC--1 will remain energized for an additional 90 seconds.
Jumper Y1 to DHUM to reduce the cooling off--delay to 5
seconds. (See Fig. 48.)
3.
Thermidistat Mode
See Fig. 27 for thermostat 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 3. above also ap-
