Carrier 160 Series - Single-Stage Cooling Operation; Single-Stage Thermostat & Two-Speed Cooling (Adaptive); Two-Stage Thermostat & Two-Speed Cooling; Thermidistat Mode Operation

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.
f. 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.
g. 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.
h. 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 in-
ducer 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 fur-
nace control CPU is factory-set for a 120-second
blower-OFF delay.
2. Two-Stage Thermostat and Two-Stage Heating
See Fig. 27-34 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 thermo-
stat R-to-W1 circuit is closed and the R-to-W2 cir-
cuit closes, the furnace contro! 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 ener-
gized. The blower motor BLWM will transition to
high-heat airflow five seconds after the R-to-W2 cir-
cuit closes.
b. Switching from High- to Low-Heat -If the thermo-
stat 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 pres-
sure 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. 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. 57. 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. Jump-
er Y/Y2 to DHUM to reduce the cooling off-delay to
5 seconds. (See Fig. 26.)
b. Single-Stage Thermostat and Two-Speed Cooling
(Adaptive Mode) -
See Fig. 34 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. 26.) 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. 57.
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
53
58CV