Carrier 58TUA - Manual (Page 12)

a. Switching from low to high gas heat—If the thermostat
R to W1 circuit for low gas heat is closed and the
R to W2 circuit for high gas heat closes, the control CPU
will switch the inducer motor IDM speed from low to high.
The high heat pressure switch relay HPSR will close. When
the inducer motor IDM provides sufficient pressure to close
the high heat pressure switch HPS, the high heat gas valve
solenoid GV is energized. The blower motor BLWM will
switch speed for high gas heat 5 sec after the R to W2
circuit closes.
b. Switching from high to low gas heat—If the thermostat
R to W2 circuit for high gas heat opens, and the R to W1
circuit for low gas heat remains closed, the control CPU
will switch the inducer motor IDM speed from high to low.
The high heat pressure switch relay HPSR will open to
de-energize the high heat gas valve solenoid GV. When the
inducer motor IDM reduces pressure sufficiently, the high
heat pressure switch HPS will open. The low heat gas valve
solenoid GV will remain energized as long as the low heat
pressure switch remains closed. The blower motor BLWM
will switch speed for low gas heat 5 sec after the R to W2
circuit opens.
3. Cooling Mode
a. Single-Speed cooling outdoor unit.
See Figure 8 for thermostat connections.
(1.) 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 circuits start the furnace blower motor
BLWM on high cooling speed.
(2.) The electronic air cleaner terminals EAC-1 and EAC-2
are energized with 115v when the blower motor
BLWM is operating.
(3.) 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 high cooling speed for an additional 90 sec.
b. Two-Speed cooling outdoor unit
See Figure 9 for thermostat connections.
(1.) The thermostat closes the R to G-and-Yl circuits for
low cooling or closes the R to G-and-Yl-and-Y2
circuits for high cooling. The R to Y1 circuit starts the
outdoor unit on low cooling speed, and the R to G
circuit starts the furnace blower motor BLWM on low
cooling speed (same speed as for low gas heat). The R
to Yl-and-Y2 circuits start the outdoor unit on high
cooling speed, and the R to G-and-Y2 circuits start
the furnace blower motor BLWM on high cooling
speed.
NOTE: Note: Y1 is found in the outdoor unit. The furnace control
CPU controls blower motor (BLWM) speed by sensing only G (for
low cooling speed) and Y2 (for high cooling speed).
(2.) The electronic air cleaner terminals EAC-1 and
EAC-2 are energized with 115v when the blower
motor BLWM is operating on either cooling speed.
(3.) When the thermostat is satisfied, the R to G-and-Yl
or R to G-and-Yl-and-Y2 circuits are opened. The
outdoor unit stops, and the furnace blower will con­
tinue operating on the cooling speed for an additional
90 sec.
4. Continuous-blower mode
a. When the R to G circuit is closed by the thermostat, the
blower motor BLWM will operate on low gas heat speed
(identical to low cooling speed. Terminals EAC-1 and
EAC-2 are energized as long as the blower motor BLWM
is energized.
b. During a call for heat, the blower BLWM will stop during
ignitor warm-up (17 sec), ignition (7 sec), and blower on
delay (45 sec), allowing the furnace heat exchangers to
quickly heat up.
c. The blower motor BLWM will revert to continuous blower
speed after the heating cycle is completed. In high gas heat,
the furnace control CPU will hold the blower motor
BLWM at high gas heat speed during the selected blower
off delay period before reverting to continuous blower
speed.
(1.) When the thermostat "calls for Low-Cooling", the
blower motor BLWM will continue to operate on low
gas heat speed. When the thermostat is satisfied, the
blower motor BLWM will continue on continuous
blower speed.
(2.) When the thermostat "calls for High-Cooling", the
blower motor BLWM will operate on high cool speed.
When the thermostat is satisfied, the blower motor
BLWM will operate an additional 2 sec on high
cooling speed before reverting back to continuous
blower speed.
(3.) When the R to G circuit is opened, the blower motor
BLWM will continue operating for an additional 90
sec if no other function requires blower motor BLWM
operation.
5. Heat Pump
NOTE: An accessory interface kit is required with single-speed
heat pumps. See interface kit Installation Instructions for single­
speed heat pump thermostat and interface connections. No inter­
face kit is needed for 2-speed heat pumps. See 2-speed heat pump
Installation Instructions for thermostat connections.
a. Single-speed heat pump cooling
(1.) The thermostat and interface kit close the R to
G-and-Y circuit to start the furnace blower motor
BLWM on high cooling speed. The Y input to the
furnace control is necessary to provide adequate cool­
ing airflow.
(2.) The electronic air cleaner terminals EAC-1 and EAC-2
are energized with 115v when the blower motor
BLWM is operating.
(3.) When the thermostat is satisfied, furnace blower motor
BLWM will continue operating on the high cooling
speed for an additional 90 sec.
b. Two-speed heat pump cooling
(1.) The thermostat closes the R to G circuits for low
cooling or closes the R to G-and-Y2 circuits for high
cooling. The thermostat R to G circuit starts the
furnace blower motor BLWM on low cooling speed.
The thermostat R to G-and-Y2 circuits start the fur­
nace blower motor BLWM on high cooling speed.
(2.) The furnace control CPU controls blower motor
BLWM speed by sensing only G for low cooling
speed and Y2 for high cooling speed.
(3.) The electronic air cleaner terminals EAC-1 and
EAC-2 are energized with 115v when the blower
motor BLWM is operating on either cooling speed.
(4.) When the thermostat is satisfied, the furnace blower
motor BLWM will continue operating on the cooling
speed for an additional 90 sec.
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