Adaptive Heating Mode; Non-Adaptive Heating Mode - Carrier 58UHV Installation, Start-Up, And Operating Instructions Manual

either low- or high-stage. After the 90-sec 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 ignitor (HSI), and gas valve (GV).
1. Adaptive Heating Mode—Single-Stage Thermostat with
2-Stage Heating (See Fig. 11 for thermostat connections.)
NOTE: In response to thermostat call for heat R to W/W1, the
control selects high-stage heating only with HIGH HEAT ONLY
switch (SW1) set to ON regardless of the LOW HEAT switch
(SW2) setting. With the HIGH HEAT ONLY switch set to OFF,
the LOW HEAT switch selects either the low-stage heating only
mode when set to ON, or the adaptive heating mode when set to
OFF in response to a thermostat call for heat R to W/W1. (See Fig.
14 for description of switch settings or Fig. 16 for control circuit
diagram.)
This furnace can operate as a 2-stage furnace with a single-
stage thermostat because the furnace control CPU includes a
programmed adaptive sequence of controlled operation, which
selects low- or high-stage gas heat operation. This selection is
based upon the stored history of the lengths of previous gas
heating on/off periods of the single-stage thermostat.
The furnace will start up in either low- or high-stage gas heat.
If the furnace starts up in low-stage, the control CPU deter-
mines the low-stage on time (from 0 to 16 minutes) which is
permitted before switching to high-stage.
If the power is interrupted, the stored history is erased. When
this happens, the control CPU selects low-stage for 16 minutes
and then switches to high-stage, as long as the thermostat
continues to call for heat. Subsequent selection is based on
stored history of the thermostat cycle times.
When the thermostat calls for heat, R-W/W1 circuit closes.
The furnace control performs a self-check, verifies that the
pressure switch contacts for low- and high-stage (LPS and
HPS) are open, and starts the IDM in low speed or high speed
as appropriate.
a. Inducer prepurge period—A 15 sec prepurge period begins
when LPS contacts close. For high-stage operation, both
LPS and HPS must be closed. For low-stage operation,
only LPS must be closed.
b. Ignitor warm-up—At the end of the prepurge period, the
HSI is energized for a 17-sec ignitor warm-up period.
c. Trial-for-ignition sequence—When the ignitor warm-up
period is completed, the main gas valve relay contacts
(MGVR-1 and -2) (and high-heat pressure switch relay
HPSR for high-stage operation) close to energize low-(and
high-) stage the gas valve solenoid(s) (GV) and the
humidifier terminal (HUM). The gas valve opens, and 24-v
power is supplied for a field-installed humidifier at termi-
nals HUM and C 24V. The GV permits gas flow to the
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burners where it is ignited. After 5 sec, the HSI is
de-energized, and a 2-sec flame-proving period begins.
If the HPS fails to close on a call for high-stage gas heat and
the LPS closes, the furnace operates at low-stage gas flow rate
until the HPS closes.
d. Flame-proving—When the burner flame is proved at the
flame-proving sensor electrode (FSE), the control CPU
begins the blower-on delay period and continues to hold
the GV open. If the burner flame is not proved within 2 sec,
the control CPU closes the GV, and the control CPU
repeats the ignition sequence for up to 3 more trials-for-
ignition before going to ignition lockout. The CONTROL
TERMINATES LOCKOUT AUTOMATICALLY after 3
hrs, or by momentarily interrupting 115-v power to the
furnace, or by interrupting 24-v power at SEC1 or SEC2 to
the control CPU (not at W/W1, G, R, etc.). Opening the
thermostat R-W circuit will not terminate an ignition
lockout.
If flame is proved when flame should not be present, the
control CPU locks out of gas heating mode and operates the
IDM on high speed until flame is no longer proved.
e. Blower-on delay—If the burner flame is proved, 45 sec
after the GV is opened the BLWM is energized at the
appropriate heating airflow: low- or high-stage CFM.
Simultaneously, the terminals EAC-1 and EAC-2 are
energized with 115v and remain energized as long as
BLWM is energized.
f. Switching from low- to high-stage gas heat—If the furnace
control CPU switches from low- to high-stage, the control
CPU switches the IDM speed from low to high. The
high-heat pressure switch relay (HPSR) closes. When the
IDM provides sufficient pressure to close the HPS, the
high-stage gas valve solenoid GV is energized. The BLWM
switches to high-stage airflow 5 sec after the control CPU
switches from low-gas heat to high-gas heat.
g. Switching from high- to low-stage gas heat—The control
CPU will not switch from high- to low-stage while the
thermostat R-W circuit is closed when a single-stage
thermostat is used.
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h. Blower-off delay—When the thermostat is satisfied, the
R-W circuit is opened, the GV is de-energized, stopping
gas flow to the burners, and terminals HUM and C
are de-energized. The IDM remains energized for a 5 sec
post-purge period. The BLWM, which had been operating
at low- or high-stage airflow, will operate at low-stage
airflow for 90 sec.
(1.) When in low-stage gas heat and the thermostat is
satisfied, the blower will continue to operate at the
low-stage gas heat CFM until the blower-off delay
reaches 90 sec. If the blower-off delay switches (on
the 2-stage furnace control) are set for more than 90
sec, the blower will operate at the selected continuous
fan CFM for the remaining blower-off delay time.
(2.) When in high-stage gas heat and the thermostat is
satisfied, the blower will continue to operate at the
high-stage gas heat CFM until the blower-off delay
expires, for all settings of the gas heat blower-off
delay switches on the 2-stage furnace control.
i. The furnace control is factory set for a 135-sec blower-off
delay.
2. Non-Adaptive Heating Mode—Two-Stage Thermostat and
2-Stage Heating (See Fig. 12 for thermostat connections).
NOTE: In response to thermostat call for heat R to W/W1 and
with HIGH HEAT ONLY switch SW1 set to OFF, the control
selects low-stage heating only with LOW HEAT switch SW2 set
to ON, or the control selects adaptive heating mode with LOW
HEAT switch SW2 set to ON. The control selects high-stage
heating only with HIGH-HEAT ONLY switch SW1 set to ON. In
response to thermostat call for high-stage heat R to W1 and W2,
the control selects high-stage heating regardless of switch SW1
and SW2 settings. See Fig. 14 for description of switch settings or
Fig. 16 for control circuit diagram.
The start-up and shutdown functions and delays described in
item 1. apply to the 2-stage heating mode as well, except for
switching from low- to high-stage and vice versa.
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24V
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