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

SETUP
SWITCH NO.
SW-1
Only High-Gas Heat
SW-2
Low-Gas Heat (Adaptive Mode)
SW-3 and SW4
Table 7—Blower-Off Delay Setup
Switch (SW) Position
DESIRED HEATING
MODE BLOWER-OFF
DELAY (SEC)
90
135
180
225
1. Adaptive Heating Mode—Single-Stage Thermostat with
2-Stage Heating (See Fig. 13 for thermostat connections.)
NOTE: In response to thermostat call for heat R to W/W1, control
selects high-heat heating only with HIGH HEAT ONLY switch
(SW1) set to ON regardless of LOW HEAT switch (SW2) setting.
With HIGH HEAT ONLY switch set to OFF, LOW HEAT switch
selects either low-heat 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 Tables 6 and 7, and Fig. 15 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 furnace control CPU includes a
programmed adaptive sequence of controlled operation, which
selects low- or high-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-gas heat. If the
furnace starts up in low-heat, the control CPU determines
low-heat on time (from 0 to 16 minutes) which is permitted
before switching to high-heat.
If power is interrupted, the stored history is erased. When this
happens, the control CPU selects low-heat for 16 minutes and
then switches to high-heat, as long as the thermostat continues
to call for heat. Subsequent selection is based on stored history
of thermostat cycle times.
When thermostat calls for heat, R-W/W1 circuit closes. The
furnace control performs a self-check, verifies that the pres-
sure switch contacts for low- and high-heat (LPS and HPS) are
open, and starts motor 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-heat operation, both
LPS and HPS must be closed. For low-heat operation, only
LPS must be closed.
b. Igniter warm-up—At end of the prepurge period, the HSI is
energized for a 17-sec igniter warm-up period.
c. Trial-for-ignition sequence—When igniter warm-up period
is completed, the main gas valve relay contacts (MGVR-1
and -2) (and high-heat pressure switch relay HPSR for
Table 6—Setup Switch Description
NORMAL
POSITION
OFF (Staged Gas Heat)
OFF (Single-Stage Thermostat)
OFF, ON
SETUP SWITCH
SW-3 SW-4
OFF OFF
OFF ON
ON OFF
ON ON
DESCRIPTION
Turn switch on to obtain only high-gas-heat operation on any call
for heat regardless of whether R-W/W1, or R-W/W1, -W2 is
closed. SW-1 overrides SW-2.
Turn switch off for installations with single-stage thermostats; con-
trol selects low-gas-heat or high-gas-heat operation based on pre-
vious cycles. Turn switch on for installations with 2-stage thermo-
stats to permit only low-gas-heat operation in response to closing
R-W/W1. High-gas heat is supplied only when R to W/W1 and W2
are closed.
Switches control gas heating mode blower-off delay. (See Table
7.)
high-heat operation) close to energize low- and high-heat
gas valve solenoid(s) (GV) and humidifier terminal
(HUM). The gas valve opens, and 24-v power is supplied
for a field-installed humidifier at terminals HUM and
C -24V. The GV permits gas flow to the burners where it
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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-gas heat and LPS
closes, the furnace operates at low-heat gas flow rate until
HPS closes.
d. Flame-proving—When burner flame is proved at flame-
proving sensor electrode (FSE), the control CPU begins the
blower-on delay period and continues to hold GV open. If
burner flame is not proved within 2 sec, the control CPU
closes 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 hr, or by momen-
tarily interrupting 115-v power to furnace, or by interrupt-
ing 24-v power at SEC1 or SEC2 to the control CPU (not
at W/W1, G, R, etc.). Opening 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 IDM
on high speed until flame is no longer proved.
e. Blower-on delay—If burner flame is proved, 45 sec after
GV is opened BLWM is energized at the appropriate
heating airflow: low- or high-heat CFM. Simultaneously,
the EAC terminals are energized with 115v and remain
energized as long as BLWM is energized.
f. Switching from low- to high-gas heat—If furnace control
CPU switches from low- to high-heat, control CPU
switches the IDM speed from low to high. The high-heat
pressure switch relay (HPSR) closes. When IDM provides
sufficient pressure to close HPS, the high-heat gas valve
solenoid GV is energized. The BLWM switches to high-
heat airflow 5 sec after the control CPU switches from
low-gas heat to high-gas heat.
g. Switching from high- to low-gas heat—The control CPU
will not switch from high- to low-gas heat while the
thermostat R-W circuit is closed when a single-stage
thermostat is used.
h. Blower-off delay—When the thermostat is satisfied, the
R-W circuit is opened, the GV is de-energized, stopping
gas flow to burners, and terminals HUM and C
de-energized. The IDM remains energized for a 5 sec
post-purge period. The BLWM, which had been operating
at low- or high-heat airflow, will operate at low-heat
airflow for 90 sec.
13
OF USE
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24v are