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•
Following the completion of pre-purge, the inducer
switches to low speed and the igniter warm up
period begins.
•
After completion of the igniter warm up period:
a. Trial for ignition begins.
b. The first stage of the gas valve is energized.
•
The igniter is de-energized when flame is sensed
or at the conclusion of the ignition activation period
(IAP), whichever comes first.
•
When flame is sensed, the delay to heat on period
begins timing.
•
After the delay to heat on period, the circulator fan
is energized at the low heat speed.
•
The EAC contact is energized with the circulator.
Call for 2nd Stage After First Stage:
•
The inducer motor goes to high speed.
•
The pressure switches are checked for closure.
Closure of the second stage pressure switch will
energize the high fire stage of the gas valve.
•
The high speed circulator output is energized.
NOTE: A call for 2
stage without a call for 1st stage
nd
will be ignored, and a three amber flash code will
be displayed on the LED. This error code will only
be stored in memory once during a single power
cycle.
2nd Stage Satisfied, First Stage Still Calling:
•
When the second stage of the thermostat is
satisfied, the inducer blower is reduced to low speed
which de-energizes the second stage of the gas
valve.
•
After the high heat off delay expires, the circulator
is reduced to low heat speed.
•
Note: A call for second stage without a call for first
stage will be ignored.
C
M
OOLING
ODE
Low stage cooling Mode sequence:
•
On a call for lo cool, the YLO and G thermostat
contacts close signaling the control module.
•
The LED will display a "GREEN"1 flash
•
The compressor and condenser fan are energized.
The compressor is connected to the YLO terminal of
the control module.
•
The circulator fan is energized at lo cool speed after
a cool on delay. The electronic air cleaner will also
be energized.
•
After the thermostat is satisfied, the compressor is
de-energized and the 45 second fan off delay period
begins.
•
Following the 45 second cool mode fan off delay
period, the cool circulator and air cleaner relay are
de-energized.
Single cooling stage thermostat or 2
sequence:
•
On a call for cool, the Y and G thermostat contacts
close signaling the control module.
•
The LED will display a "GREEN"2 flash
•
The compressor and condenser fan are energized.
The circulator fan is energized at cool speed after a
cool on delay. The electronic air cleaner will also be
energized.
•
After the thermostat is satisfied, the compressor is
de-energized and the fan off delay period begins.
•
Following the 45 second fan off delay period, the
cool circulator and air cleaner relay are de-energized.
Note: If a call for both YLO and Y are present, Y will have
priority.
F
O
M
AN
NLY
ODE
MANUAL FAN ON:
•
Call for continuous fan (24 volts on the furnace "G"
terminal.)
•
The LED will display rapid "GREEN".
•
The circulator blower and the electronic air cleaner
terminal are energized.
O
C
PERATIONAL
HECKS
The burner flames should be inspected with the burner compart-
ment door installed. Flames should be stable, quiet, soft, and
blue (dust may cause orange tips but they must not be yellow).
Flames should extend directly outward from the burners without
curling, floating, or lifting off. Flames must not impinge on the
sides of the heat exchanger firing tubes.
S
C
D
AFETY
IRCUIT
ESCRIPTION
A number of safety circuits are employed to ensure safe and
proper furnace operation. These circuits serve to control any
potential safety hazards and serve as inputs in the monitoring
and diagnosis of abnormal function. These circuits are continu-
ously monitored during furnace operation by the integrated con-
trol module.
I
C
M
NTEGRATED
ONTROL
The integrated control module is an electronic device which, if a
potential safety concern is detected, will take the necessary pre-
cautions and provide diagnostic information through an LED.
P
L
RIMARY
IMIT
The primary limit control is located on the partition panel and
monitors heat exchanger compartment temperatures. It is a
normally-closed (electrically), automatic reset, temperature-ac-
tivated sensor. The limit guards against overheating as a result
of insufficient conditioned air passing over the heat exchanger.
50
stage cooling Mode
nd
ODULE
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Troubleshooting
