45
•
Circulator blower and electronic air cleaner terminal
is de-energized.
•
Circulator blower ramps down to OFF during the 30
seconds following the heat off delay period.
•
Furnace awaits next call from thermostat.
C
OOLING
M
ODE
The normal operational sequence in cooling mode is as
follows:
•
R and Y1/G or Y2/G thermostat contacts close,
initiating a call for cool.
•
Integrated control module performs safety circuit
checks.
•
Outdoor fan and compressor are energized to their
appropriate speed.
•
Circulator blower is energized on the appropriate
cool speed at the level and time determined by the
selected ramping profile. Electronic air cleaner
terminal is energized with circulator blower.
•
Furnace circulator blower and outdoor cooling unit
run their appropriate speeds, integrated control
module monitors safety circuits continuously.
•
R and Y1/G or Y2/G thermostat contacts open,
completing the call for cool.
•
Outdoor fan and compressor are de-energized.
•
Circulator blower continues running during a cool
off delay period. The OFF delay time and airflow
level are determined by the selected ramping profile.
•
Electronic air cleaner terminal and circulator blower
are de-energized.
•
Furnace awaits next call from thermostat.
F
AN
O
NLY
M
ODE
The normal operational sequence in fan only mode is as
follows:
•
R and G thermostat contacts close, initiating a call
for fan.
•
Integrated control module performs safety circuit
checks.
•
Circulator blower is energized on continuous fan
speed (25, 50, 75 or 100% of the furnace’s maximum
airflow capability. Fan speed selected by dip
switches) following a five (5) second delay. Electronic
air cleaner terminal is energized.
•
Circulator blower runs, integrated control module
monitors safety circuits continuously.
•
R and G thermostat contacts open, completing the
call for fan.
•
Circulator blower is de-energized. Electronic air
cleaner terminal is de-energized.
•
Furnace awaits next call from thermostat.
O
PERATIONAL
C
HECKS
The burner flames should be inspected with the burner
compartment 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.
Burner Flame
Figure 57
S
AFETY
C
IRCUIT
D
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 continuously monitored during furnace operation
by the integrated control module.
I
NTEGRATED
C
ONTROL
M
ODULE
The integrated control module is an electronic device which,
if a potential safety concern is detected, will take the
necessary precautions and provide diagnostic information
through an LED.
P
RIMARY
L
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-activated sensor. The limit guards against
overheating as a result of insufficient conditioned air passing
over the heat exchanger.
A
UXILIARY
L
IMIT
The auxiliary limit controls are located on or near the
circulator blower and monitors blower compartment
temperatures. They are a normally-closed (electrically),
manual-reset sensors. These limits guard against
overheating as a result of insufficient conditioned air passing
over the heat exchanger.
R
OLLOUT
L
IMIT
The rollout limit controls are mounted on the burner/manifold
assembly and monitor the burner flame. They are normally-
closed (electrically), manual-reset sensors. These limits guard
against burner flames not being properly drawn into the heat
exchanger.
