Bryant 333JAV Installation, Start-Up, And Operating Instructions Manual page 15

terminal (HUM). The gas valve opens, and 24-v power is
supplied for a field-installed humidifier at terminals
HUM and C 24v. The GV permits gas flow to the
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burners where it is ignited. After 5 sec, the HSI is
de-energized, and a 2-sec flame-proving period begins.
If the HPS fails to close on a call for high-gas heat and LPS closes,
the furnace operates at low-heat gas flow rate until HPS closes.
d. Flame-proving—When burner flame is proved at flame-
proving sensor electrode (FSE), the control CPU begins
the blower-on delay period and continues to hold GV
open. If burner flame is not proved within 2 sec, the
control CPU closes GV, and the control CPU repeats the
ignition sequence for up to 3 more trials-for-ignition
before going to ignition lockout. The CONTROL TER-
MINATES LOCKOUT AUTOMATICALLY after 3 hr,
or by momentarily interrupting 115-v power to furnace,
or by interrupting 24-v power at SEC1 or SEC2 to the
control CPU (not at W/W1, G, R, etc.). Opening
thermostat R-W circuit will not terminate an ignition
lockout.
If flame is proved when flame should not be present, the control
CPU locks out of gas heating mode and operates IDM on high
speed until flame is no longer proved.
e. Blower-on delay—If burner flame is proved, 45 sec after
GV is opened BLWM is energized at the appropriate
heating airflow: low- or high-heat CFM. Simultaneously,
the EAC terminals are energized with 115v and remain
energized as long as BLWM is energized.
f. Switching from low- to high-gas heat—If furnace control
CPU switches from low- to high-heat, control CPU
switches the IDM speed from low to high. The high-heat
pressure switch relay (HPSR) closes. When IDM pro-
vides sufficient pressure to close HPS, the high-heat gas
valve solenoid GV is energized. The BLWM switches to
high-heat airflow 5 sec after the control CPU switches
from low-gas heat to high-gas heat.
g. Switching from high- to low-gas heat—The control CPU
will not switch from high- to low-gas heat while the
thermostat R-W circuit is closed when a single-stage
thermostat is used.
h. Blower-off delay—When the thermostat is satisfied, the
R-W circuit is opened, the GV is de-energized, stopping
gas flow to burners, and terminals HUM and C
de-energized. The IDM remains energized for a 5 sec
post-purge period. The BLWM, which had been operat-
ing at low- or high-heat airflow, will operate at low-heat
airflow for 90 sec.
(1.) When in low-gas heat and thermostat is satisfied,
blower will continue to operate at low-gas heat
CFM until the blower-off delay reaches 90 sec. If
blower-off delay switches (on the 2-stage furnace
control) are set for more than 90 sec, blower will
operate at the selected continuous fan CFM for
remaining blower-off delay time.
(2.) When in high-gas heat and thermostat is satisfied,
blower will continue to operate at high-gas heat
CFM until the blower-off delay expires, for all
settings of the gas heat blower-off delay switches on
the 2-stage furnace control.
i. The furnace control is factory set for a 135-sec blower-
off delay.
2. Non-Adaptive Heating Mode—Two-Stage Thermostat and
2-Stage Heating (See Fig. 17 for thermostat connections).
NOTE: In response to thermostat call for heat R to W/W1 and
with HIGH HEAT ONLY switch SW1 set to OFF, the control
selects low-heat only with LOW HEAT switch SW2 set to ON, or
the control selects adaptive heating mode with LOW HEAT switch
SW2 set to ON. The control selects high-heat only with HIGH-
HEAT ONLY switch SW1 set to ON. In response to thermostat
call for high-gas heat R to W1 and W2, the control selects
high-heat regardless of switch SW1 and SW2 settings. See Tables
6 and 7, and Fig. 18 for description of switch settings or Fig. 19 for
control circuit diagram.
The start-up and shutdown functions and delays described in item
1 apply to 2-stage heating mode as well, except for switching from
low- to high-gas heat and vice versa.
a. When thermostat calls for heat, the R-W/W1 circuit
b. Switching from low- to high-gas heat—If the thermostat
c. Switching from high- to low-gas heat—If thermostat
3. Cooling Mode
a. Single-Speed Cooling Outdoor Unit (See Fig. 16 for
24v are
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b. Two-Speed Cooling Outdoor Unit (See Fig. 17 for
—15—
closes for low-gas heat or the R to W1-and-W2 circuits
close for high-gas heat. The furnace control performs a
self-check, verifies pressure switch contacts for low- and
high-heat LPS and HPS are normally open, and starts
IDM in low speed or high speed as appropriate.
R-W/W1 circuit for low-gas heat is closed and the R-W2
circuit for high-gas heat closes, the control CPU
switches IDM speed from low to high. The HPSR closes.
When IDM provides sufficient pressure to close HPS,
high-heat gas valve solenoid GV is energized. The
BLWM switches to high-stage airflow 5 sec after R-W2
circuit closes.
R-W2 circuit for high-stage opens and R-W/W1 circuit
for low-gas heat remains closed, the control CPU
switches IDM speed from high to low. The HPSR opens
to de-energize high-heat gas valve solenoid GV. When
IDM reduces pressure sufficiently, HPS opens. The
low-heat gas valve solenoid GV remains energized as
long as LPS remains closed. The BLWM switches to
low-heat airflow 5 sec after R-W2 circuit opens.
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/Y2 circuits start the furnace BLWM on cooling
speed.
(2.) The EAC terminals are energized with 115v when
BLWM is operating.
(3.) When thermostat is satisfied, the R to G-and-Y
circuits are opened. The outdoor unit stops, and
furnace BLWM continues operating at cooling air-
flow for an additional 90 sec.
thermostat connections.)
(1.) The thermostat closes the R to G-and-Y1 circuits
for low cooling or closes the R to G-and-Y1-and-
Y/Y2 circuits for high cooling. The R to Y1 circuit
operates the outdoor unit on low-cooling speed. The
R to G-and-Y1 circuit operates the furnace BLWM
at low-cooling airflow (65 percent of single-speed
cooling airflow; different airflow than for low-gas
heat). The R to Y1-and-Y2 circuits operate the
outdoor unit on high-cooling airflow, and the R to
G-and-Y/Y2-and-Y1 circuits
BLWM at high-cooling airflow. Two-speed high-
cooling airflow is 105 percent of single-speed
cooling airflow.
operate furnace