Manual 2100-366
Page 3
SECTION 3 • UNDERSTANDING HOW
YOUR FURNACE WORKS
Your installer should have given you a detailed
explanation of how the furnace operates. Shown
below are the basic operation characteristics and
sequence of operation. If you have any questions
consult your installer and/or service agency.
2.3 ALTERATION OF FURNACE CONTROLS
WARNING
Do not alter any gas or electrical controls
(gas control or safety controls) in any
manner. Altering them could cause
furnace to operate unsafely resulting in
damage, injury or death.
* * IMPORTANT * *
There are many types of thermostats
compatible with this furnace. Make sure
you understand the specific type installed.
Ask installer for detailed explanation, and
retain thermostat instruction manual for
reference.
This furnace is equipped with a vent shut-off system
which monitors the combustion air into the burners by
means of a pressure sensing device. When the vent
becomes blocked, this device turns off the gas valve
circuit to prevent flue products from entering the
structure. In the event that this occurs, shut off
furnace and contact a qualified service agency.
3.1 BASIC OPERATION – HEATING CYCLE
This furnace is operated by an Integrated Furnace
Control (IFC) and a gas control system which controls
all functions of the furnace.
On a call for heat from the thermostat, the IFC first
turns on the inducer motor. The pressure switch then
closes signaling the ignition control to proceed with
ignition function.
The ignition system consists of a direct spark igniter
(DSI) and remote sensor. When the thermostat calls
for heat the DSI sparks to light main burner gas.
Once ignited the remote sensor confirms flame
carryover to all burners.
There is a 60 second delay after main burner is on
until the comfort air blower starts on heating speed.
After the thermostat is satisfied, the burners will go
off as gas valve closes. The inducer will continue to
run for 30 seconds, and the comfort air blower will
continue to run for 2-1/2 minutes.
3.2 BASIC OPERATION – COOLING CYCLE
On a call for cool the compressor and condenser fan
will start immediately, and the comfort air blower will
start 7 seconds later on cooling speed.
Note: Some
models may be equipped with optional Low Ambient
Control that will cycle the condenser fan motor to
maintain proper refrigerant pressures under lower
outdoor temperature conditions. When the thermostat
is satisfied the compressor and condenser fan will stop
and the comfort air blower will continue to operate for
60 seconds.
3.2.1 COMPRESSOR CONTROL MODULE
(CCM)
All models are equipped with a compressor control
module. This control is an anti-short cycle/lockout
timer with high and low pressure switch monitoring
and alarm relay output.
Delay on Make Timer and Break Time Delay
• On initial power up, or any time the power is
interrupted to the unit, the delay on make
period begins. This delay will be 2 minutes
plus 10% of the delay on break setting. This
feature assures that pressures will be equalized
for normal start up if there are brief power
interruptions, and can accommodate staggered
starts for dual unit installations as long as the
off delay periods are set differently for the two
units.
• During routine operation of the unit with no
power interruptions the compressor will
operate on demand with no delay as long as off
delay time has been met.
• Adjustable 30 second to 5 minute delay on break
timer assures that pressures can equalize if units
are short cycled by the operating controls or
personnel. Recommended settings would be 2
minutes for unit 1 and 3 minutes for Unit 2.
