Bryant CONDENSING GAS FURNACE 350MAV Скачать руководство пользователя страница 35

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gas heating. The Amber LED light will flash code 12 during the
90-second period, after which the LED will be ON continuous, as
long as no faults are detected. After the 90-second period, the
furnace will respond to the thermostat normally.

The blower door must be installed for power to be conducted
through the blower door interlock switch ILK to the furnace
control CPU, transformer TRAN, inducer motor IDM, blower
motor BLWM, hot-surface igniter HSI, and gas valve GV.

Heating Mode

(See Fig. 27 for thermostat connections.)

The wall thermostat

″

calls for heat,

″

closing the R to W

circuit. The furnace control performs a self-check, verifies
the pressure switch contacts PRS are open, and starts the
inducer motor IDM.

a. Inducer Prepurge Period- As the inducer motor IDM

comes up to speed, the pressure switch contacts PRS
close to begin a 15-second prepurge period.

b. Ignitor Warm-Up- At the end of the prepurge period,

the Hot-Surface igniter HSI is energized for a 17-second
igniter warm-up period.

c. Trial-for-Ignition

Sequence-

When

the

igniter

warm-up period is completed the main gas valve relay
contacts GVR-1 and -2 close to energize the gas valve
GV, the gas valve opens, and 24 vac power is supplied
for a field-installed humidifier at the HUM terminal. The
gas valve GV permits gas flow to the burners where it is
ignited by the Hot Surface Ignitor HSI. Five seconds afte
the GVR-1 closes, a 2-second flame period begins. The
HSI igniter will remain energized until the flame is
sensed or until the 2-second flame proving period begins.

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 momen-
tarily interrupting 115 vac power to the furnace, or by
interrupting 24 vac power at SEC1 or SEC2 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 66 seconds
(040 through 120 sizes) or 45 seconds (140 size) 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. Blower-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-energizing
the humidifier terminal HUM. The inducer motor IDM
will remain energized for a 15-second (040 through 120
sizes) or 5-second (140 size) post-purge period. The
blower motor BLWM and air cleaner terminal EAC-1
will remain energized for 90, 120, 150, or 180 seconds
(depending on the blower-OFF delay selection). The
furnace control CPU is factory-set for a 120-second
blower-OFF delay.

Cooling Mode

The thermostat “calls for cooling.”

a. Single-Speed Cooling

(See Fig. 27, 48, 50, and 52 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 COOL speed.
The electronic air cleaner terminal EAC-1 is energized
with 115 vac when the blower motor BLWM is operat-
ing.
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 on
the COOL speed for an additional 90 seconds. Jumper
Y/Y2 to DHUM to reduce the cooling off-delay to 5
seconds. (See Fig. 31.)

b. Two-Speed Cooling

(See Fig. 27, 49, 51, 53, and 54 for thermostat connec-
tions.)

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 on low-cool
speed (same speed as FAN). 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 on COOL speed.
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. 31.)