Cooling Mode; Continuous Blower Mode; Heat Pump Mode - Carrier 58UHV Installation, Start-Up, And Operating Instructions Manual

a. When the thermostat calls for heat, the R-W/W1 circuit
closes for low-stage or the R to W1-and-W2 circuits close
for high-stage. The furnace control performs a self-check,
verifies pressure switch contacts for low- and high-stage
LPS and HPS are normally open, and starts the IDM in low
speed or high speed as appropriate.
b. Switching from low- to high-stage gas heat—If the ther-
mostat R-W/W1 circuit for low-stage is closed and the
R-W2 circuit for high-stage closes, the control CPU
switches the IDM speed from low to high. The HPSR
closes. When the IDM provides sufficient pressure to close
the HPS, the high-stage gas valve solenoid GV is ener-
gized. The BLWM switches to high-stage airflow 5 sec
after the R-W2 circuit closes.
c. Switching from high- to low-stage gas heat—If the ther-
mostat R-W2 circuit for high-stage opens and the R-W/W1
circuit for low-stage remains closed, the control CPU
switches the IDM speed from high to low. The HPSR opens
to de-energize the high-stage gas valve solenoid GV. When
the IDM reduces pressure sufficiently, the HPS opens. The
low-stage gas valve solenoid GV remains energized as long
as the LPS remains closed. The BLWM switches to
low-stage airflow 5 sec after the R-W2 circuit opens.

3. Cooling Mode

a. Single-Speed Cooling Outdoor Unit (See Fig. 11 for
thermostat connections.)
(1.) The thermostat closes the R to G-and-Y circuits. The
R-Y circuit starts the outdoor unit, and the R to
G-and-Y/Y2 circuits start the furnace BLWM on
cooling speed.
(2.) The terminals EAC-1 and EAC-2 are energized with
115v when the BLWM is operating.
(3.) When the thermostat is satisfied, the R to G-and-Y
circuits are opened. The outdoor unit stops, and the
furnace BLWM continues operating at cooling airflow
for an additional 90 sec.
b. Two-Speed Cooling Outdoor Unit (See Fig. 12 for thermo-
stat 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% 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 operate the furnace BLWM at high-cooling
airflow. Two-speed high-cooling airflow is 105% of
single-speed cooling airflow.
NOTE: Y1 is found in the outdoor unit. The furnace control CPU
controls BLWM airflow by sensing only G-and-Y1 for low-
cooling airflow and G-and-Y1-and-Y/Y2 for high-cooling airflow.
(2.) Terminals EAC-1 and EAC-2 are energized with 115v
when the BLWM is operating on either cooling
airflow.
(3.) When the thermostat is satisfied, the R to G-and-Y1
or R to G-and-Y1-and-Y/Y2 circuits open. The out-
door unit stops, and the furnace blower continues
operating on the same cooling airflow for an addi-
tional 90 sec.
4. Continuous-Blower Mode
a. When the R to G circuit is closed by the thermostat, the
BLWM operates at LOW, MED, or HI (50%, 65%, or
100% of single-speed cooling airflow; different than low-
gas heat airflow). LOW, MED, and HI selections are
described in Set-up Procedures. Terminals EAC-1 and
EAC-2 are energized with 115v as long as the BLWM is
operating.
b. During a call for heat, the BLWM stops during ignitor
warm-up (17 sec), ignition (7 sec), and blower-on delay (45
sec), allowing the furnace heat exchangers to heat up
quickly, after which the BLWM operates at the appropriate
gas heating airflow.
c. The BLWM reverts to continuous-blower airflow after the
heating cycle is completed. In high-stage gas heating, the
furnace control CPU and ICM2+ motor control hold the
BLWM at low-stage airflow for a 90-sec blower-off delay
period (regardless of selected blower-off delay) before
reverting to continuous-blower airflow.
d. When the thermostat calls for low-cooling, the BLWM
switches to low-cool airflow or the selected continuous-
blower airflow, whichever is greater. Note that a HI
selection for continuous-blower airflow will provide more
than normal airflow during 2-speed low-cooling. When the
thermostat is satisfied, the BLWM switches to continuous-
blower airflow.
e. When the thermostat calls for high cooling, the BLWM
operates at high-cool airflow. When the thermostat is
satisfied, the BLWM operates an additional 2 sec at
high-cool airflow before reverting back to continuous-
blower airflow.
f. When the R-G circuit is opened, the BLWM continues
operating for an additional 90 sec, if no other function
requires BLWM operation.

5. Heat Pump Mode

NOTE: A dual-fuel thermostat or accessory interface kit is
required with single-speed heat pumps. See dual-fuel thermostat or
interface kit Installation Instructions 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 Instruc-
tions to determine whether a standard or dual-fuel heat pump
thermostat is required and for thermostat connections.
NOTE: See TSTAT Price Page for dual-fuel thermostat ordering
number.
a. Single-Speed Heat Pump Cooling
(1.) The thermostat and interface kit close the R to
Y/Y2-and-G-and-O circuits to operate the furnace
BLWM at cooling airflow. The Y/Y2 input to the
furnace control is necessary to provide adequate cool-
ing airflow.
(2.) Terminals EAC-1 and EAC-2 are energized with 115v
when the BLWM is operating.
(3.) When the thermostat is satisfied, furnace BLWM
continues operating at the cooling airflow for an
additional 90 sec.
b. Two-Speed Heat Pump Cooling
(1.) The thermostat R to G-and-Y1-and-O circuits operate
the furnace BLWM at low-cool airflow. The thermo-
stat R to G-and-Y/Y2-and-Y1-and-O circuits operate
the furnace BLWM at high-cool airflow (105% of
single-speed cooling airflow).
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