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If the ACTION is a question (a question will have a number in the
YES or NO column), answer it YES or NO. If the answer is YES,
go to the step indicated in the YES column. If the answer is NO,
go to the step indicated in the NO column.
Let's try our guide out using the EXAMPLE section below, and
see how it works. Suppose that the problem is a defective low heat
pressure switch (for example the contacts will not open). This is an
internal problem and cannot simply be seen. We go to the START
HERE section to Step 1.
STEP
Step 1 tells us to remove main furnace door first and NOT
TO REMOVE THE BLOWER ACCESS PANEL. It then asks
the question, "Is AMBER LED status light on?". If the low
1.
heat pressure switch was defective, a pressure switch did
not open status code would be flashing, so the answer is
Step 2 asks the question, "Is the AMBER LED status light
blinking rapidly without a pause?". If the low heat pressure
2.
switch was defective, a pressure switch did not open status
code would be flashing, so the answer is NO. We go to
Step 4 asks the question, "Is the AMBER LED status light
blinking ON/OFF slowly with a combination of short and
4.
long flashes?". If the low heat pressure switch was defec-
tive, a pressure switch did not open status code would be
flashing, so the answer is YES. We go to Step 5.
Step 5 tells us to determine the status code. The status
code is a 2 digit number with the first digit determined by
the number of short flashes and the second digit by the
5.
number of long flashes. So we count the short and long
flashes and see that status code 23 is flashing and go to
6.
GENERAL
The furnace must have a 115-vac power supply properly connected
and grounded. Correct polarity must be maintained to enable gas
heating operation.
The gas service pressure must not exceed 0.5 psig (14-in.wc), and
no less than 0.16 psig (4.5-in.wc).
Thermostat wire connections to the furnace at R and W/W1 are the
minimum required for gas heating operation. W2 must be con-
nected for 2-stage heating thermostats. Y/Y2 and G are required to
be connected to the furnace for single-stage cooling and heat
pumps. Y1, Y/Y2, and G are required for two-stage cooling and
heat pumps. G is required for continuous-fan. C
for some clock thermostats. These connections must be made at the
24-vac terminal block on the furnace control (See Appendix A).
This furnace can be installed with either a single-stage heat/cool or
a two-stage heat/cool thermostat.
This furnace is equipped with a manual reset limit switch in
the gas control area. The switch will open and shut off power
to the gas valve, if a flame rollout or overheating condition
occurs in the gas control area. DO NOT bypass the switch.
Correct inadequate combustion-air supply and/or component
failure before resetting the switch. Failure to follow this
caution could result in premature product failure.
Before operating the furnace, check each manual reset switch for
continuity. If necessary, press and release the button to reset the
switch.
ACTION
YES. We go to Step 2.
Step 4.
Step 6.
Step 6 tells us to go to status code 23 section.
-24V is required
OM
SEQUENCE OF OPERATION
Using the schematic diagram in Appendix A, follow the sequence
of operation through the different modes. Read and follow the
wiring diagram very carefully.
NOTE: If a power interruption occurs during a call for heat
(W/W1 or W/W1-and-W2), the control will start a 90-second
blower-only ON period two seconds after power is restored, if the
thermostat is still calling for gas heating. The amber LED light will
Example
Start Here
flash code 12 during the 90-second period, after which the LED
will be ON continuous, as long as no faults are detected. After the
90-second period, the furnace will respond to the thermostat
normally.
The blower access panel 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 igniter HSI, and gas valve GV.
Step 1—Single-Stage Thermostat and Two-Stage
Heating (Adaptive Mode)
NOTE: The low-heat only switch SW1-2 selects either the
low-heat only operation mode when ON, (see sequence 2. below)
or the adaptive heating mode when OFF in response to a call for
heat. (See Fig. 1.) When the W2 thermostat terminal is energized
it will always cause high-heat operation when the R to W circuit is
closed, regardless of the setting of the low-heat only switch.
This furnace can operate as a two-stage furnace with a single-stage
thermostat because the furnace control CPU includes a pro-
grammed adaptive sequence of controlled operation, which selects
low-heat or high-heat operation. This selection is based upon the
stored history of the length of previous gas-heating periods of the
single-stage thermostat.
The furnace will start up in either low- or high-heat. If the furnace
starts up in low-heat, the control CPU determines the low-heat
on-time (from 0 to 16 minutes) which is permitted before switch-
ing to high-heat.
If the power is interrupted, the stored history is erased and the
control CPU will select low-heat for up to 16 minutes and then
3
YES
NO
2
19
3
4
5
7
GO TO
6
INDEX
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