User Manual

Manual 2100-502
Page 5 of 15
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
* * 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 carry over 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.
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.