Operating instructions

self-check, verifies low-heat and high-heat pressure
switch contacts LPS and HPS are open, and starts
inducer motor IDM in low speed or high speed as
appropriate.
b. Switching from low- to high-gas heat—If thermostat
R-W/W1 circuit for low-gas heat is closed and R-W2
circuit for high-gas heat closes, control CPU switches
inducer motor IDM speed from low to high. The
high-heat pressure switch relay HPSR closes. When
inducer motor IDM provides sufficient pressure to close
high-heat pressure switch HPS, high-heat gas valve
solenoid GV is energized. Blower motor BLWM
switches speed for high-gas heat 5 sec after R-W2 circuit
closes.
c. Switching from high- to low-gas heat—If thermostat
R-W2 circuit for high-gas heat opens and R-W/W1
circuit for low-gas heat remains closed, control CPU
switches inducer motor IDM speed from high to low.
The high-heat pressure switch relay HPSR opens to
de-energize high-heat gas valve solenoid GV. When
inducer motor IDM reduces pressure sufficiently, high-
heat pressure switch HPS opens. The low-heat gas valve
solenoid GV remains energized as long as low-heat
pressure switch LPS remains closed. Blower motor
BLWM switches speed for low-gas heat 5 sec after
R-W2 circuit opens.
3. Cooling Mode
a. Single-Speed Cooling Outdoor Unit
(See Fig. 15 for thermostat connections.)
(1.) The thermostat closes R to G-and-Y circuits. The
R-Y circuit starts outdoor unit, and R to G-and-Y
circuits start furnace blower motor BLWM on
high-cool speed.
(2.) The EAC terminals EAC-1 and EAC-2 are ener-
gized with 115v when blower motor BLWM is
operating.
(3.) When thermostat is satisfied, R to G-and-Y cir-
cuits are opened. The outdoor unit stops, and
furnace blower motor BLWM continues operating
on high-cool speed for an additional 90 sec.
b. Two-Speed Cooling Outdoor Unit
(See Fig. 16 for thermostat connections.)
(1.) The thermostat closes R to G-and-Y1 circuits for
low cooling or closes R to G-and-Y1-and-Y/Y2
circuits for high cooling. The R-Y1 circuits start
outdoor unit on low-cooling speed, and R-G circuit
starts furnace blower motor BLWM on low-cooling
speed (same speed as for low-gas heat). The R to
Y1-and-Y2 circuits start outdoor unit on high-
cooling speed, and R to G-and-Y2 circuits start
furnace blower motor BLWM on high-cooling
speed.
NOTE: Y1 is not located on furnace control, but is found in
outdoor unit. The furnace control CPU controls blower motor
BLWM speed by sensing only G for low-cooling speed and Y/Y2
for high-cooling speed.
(2.) The EAC terminals EAC-1 and EAC-2 are ener-
gized with 115v when blower motor BLWM is
operating on either cooling speed.
(3.) When thermostat is satisfied, R to G-and-Y1 or
R to G-and-Y1-and-Y/Y2 circuits open. The out-
door unit stops, and furnace blower continues op-
erating on cooling speed for an additional 90 sec.
4. Continuous Blower Mode
a. When R to G circuit is closed by thermostat, blower
motor BLWM operates on low-gas-heat speed (identical
to low-cool speed). Terminals EAC-1 and EAC-2 are
energized with 115v as long as blower motor BLWM is
energized.
b. During "call for heat," blower motor BLWM stops
during ignitor warm-up (17 sec), ignition (7 sec), and
blower on delay (45 sec), allowing furnace heat ex-
changers to heat up quickly.
(1.) The blower motor BLWM reverts to continuous
blower speed after heating cycle is completed. In
high-gas-heat, furnace control CPU holds blower
motor BLWM at high-gas-heat speed during se-
lected blower off delay period before reverting to
continuous blower speed.
(2.) When thermostat "calls for low cooling," blower
motor BLWM continues to operate on low-cool
speed. When thermostat is satisfied, blower motor
BLWM continues on continuous blower speed.
(3.) When thermostat "calls for high cooling," blower
motor BLWM operates on high-cool speed. When
thermostat is satisfied, blower motor BLWM oper-
ates an additional 2 sec on high-cool speed before
reverting back to continuous blower speed.
(4.) When R to G circuit is opened, blower motor
BLWM continues operating for an additional 90 sec
if no other function requires blower motor BLWM
operation.
5. Heat Pump
NOTE: An accessory interface kit or manufacturing accessory
dual fuel thermeostat is required with single-speed heat pumps.
See interface kit Installation Instructions or manufacturing acces-
sory dual fuel thermostat for single-speed heat pump thermostat
and interface connections. No interface kit is needed for 2-speed
heat pumps. See 2-speed heat pump Installation Instructions for
thermostat connections.
a. Single-Speed Heat Pump Cooling
(1.) The thermostat and interface kit close R to G-and-
Y/Y2 circuit to start furnace blower motor BLWM
on high-cooling speed. (Y/Y2 input to furnace
control is necessary to provide adequate cooling
airflow.)
(2.) The EAC terminals EAC-1 and EAC-2 are ener-
gized with 115v when blower motor BLWM is
operating.
(3.) When thermostat is satisfied, furnace blower motor
BLWM continues operating on high-cooling speed
for an additional 90 sec.
b. Two-Speed Heat Pump Cooling
(1.) The thermostat R to G circuits start furnace blower
motor BLWM on low-cooling speed. Thermostat
R to G-and-Y/Y2 circuits start furnace blower mo-
tor BLWM on high-cool speed.
NOTE: The furnace control CPU controls blower motor BLWM
speed by sensing only G (for low-cooling speed) and Y2 (for
high-cooling speed).
(2.) The EAC terminals EAC-1 and EAC-2 are ener-
gized with 115v when blower motor BLWM is
operating on either cooling speed.
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