Carrier A Series Installation, Start-Up, Operating And Service And Maintenance Instructions page 43

PG80VTLA: Installation, Start-up, Operating and Service and Maintenance Instructions
d. Flame-Proving - When the burner flame is proved at the
flame-proving sensor electrode FSE, the inducer motor IDM
switches to low-speed unless the furnace is operating in
high-heat, and the furnace control CPU begins the blower-ON
delay period and continues to hold the gas valve GV-M open. If
the burner flame is not proved within two seconds, the control
CPU will close the gas valve GV-M, 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 furnace, or by interrupting 24
vac power at SEC1 or SEC2 to the furnace control CPU (not at
W/W1, 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 on high speed until
flame is no longer proved.
e. Blower-On delay - If the burner flame is proven the blower-ON
delays for low-heat and high-heat are as follows:
Low-heat - 45 seconds after the gas valve GV-M is opened the blower
motor BLWM is turned ON at low-heat airflow.
High-heat - 25 seconds after the gas valve GV-M is opened the BLWM
is turned ON at high-heat airflow. Simultaneously, the humidifier
terminal HUM and electronic air cleaner terminal EAC-1 are energized
and remain energized throughout the heating cycle.
a. Switching from Low- to High-Heat - If the furnace control
CPU switches from low-heat to high-heat, the furnace control
CPU will switch the inducer motor IDM speed from low to high.
The high-heat pressure switch relay HPSR is de-energized to
close the NC contact. When sufficient pressure is available the
high-heat pressure switch HPS closes, and the high-heat gas
valve solenoid GV-HI is energized. The blower motor BLWM
will transition to high-heat airflow five seconds after the furnace
control CPU switches from low-heat to high-heat.
b. Switching from High- to Low-Heat -The furnace control CPU
will not switch from high-heat to low-heat while the thermostat
R-to-W circuit is closed when using a single-stage thermostat.
c. Blower-Off Delay -When the thermostat is satisfied, the R to W
circuit is opened, de-energizing the gas valve GV-M, stopping
gas flow to the burners, and de-energizing the humidifier
terminal HUM. The inducer motor IDM will remain energized
for a 5-second post-purge period. The blower motor BLWM and
air cleaner terminal EAC-1 will remain energized at low-heat
airflow or transition to low-heat airflow for 90, 120, 150, or 180
seconds (depending on selection at blower-OFF delay switches).
The furnace control CPU is factory-set for a 120-second
blower-OFF delay.
2. Two-Stage Thermostat and Two-Stage Heating
See Fig. 28 - Fig. 35 for thermostat connections
NOTE: In this mode the low-heat only switch SW1-2 must be ON to
select the low-heat only operation mode in response to closing the
thermostat R-to-W1 circuit. Closing the thermostat R-to- W1-and-W2
circuits always causes high-heat operation, regardless of the setting of
the low-heat only switch.
The wall thermostat "calls for heat", closing the R-to-W1 circuit for
low-heat or closing the R-to-W1-and-W2 circuits for high-heat. The
furnace control performs a self-check, verifies the low-heat and
high-heat pressure switch contacts LPS and HPS are open, and starts the
inducer motor IDM in high-speed.
The start up and shut down functions and delays described in item 1.
above apply to the 2-stage heating mode as well, except for switching
from low- to high-Heat and vice versa.
a. Switching from Low- to High-Heat - If the thermostat R-to-W1
circuit is closed and the R-to-W2 circuit closes, the furnace
control CPU will switch the inducer motor IDM speed from low
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
to high. The high-heat pressure switch relay HPSR is
de-energized to close the NC contact. When sufficient pressure is
available the high-heat pressure switch HPS closes, and the
high-heat gas valve solenoid GV-HI is energized. The blower
motor BLWM will transition to high-heat airflow five seconds
after the R-to-W2 circuit closes.
b. Switching from High- to Low-Heat -If the thermostat R-to- W2
circuit opens, and the R-to-W1 circuit remains closed, the
furnace control CPU will switch the inducer motor IDM speed
from high to low. The high-heat pressure switch relay HPSR is
energized to open the NC contact and de-energize the high-heat
gas valve solenoid GV-HI. When the inducer motor IDM reduces
pressure sufficiently, the high-heat pressure switch HPS will
open. The gas valve solenoid GV-M will remain energized as
long as the low-heat pressure switch LPS remains closed. The
blower motor BLWM will transition to low-heat airflow five
seconds after the R-to-W2 circuit opens.
3. Cooling mode
The thermostat "calls for cooling".
a. Single-Speed Cooling-
See Fig. 28 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
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-delay to 5 seconds. (See
b. Single-Stage Thermostat and Two-Speed Cooling (Adaptive
Mode) -
See Fig. 35 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 sequence 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. 36). 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.
(See Fig. 55).
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
43
Fig. 55).
Fig. 36).