
44
START-UP PROCEDURES
DIRECT SPARK IGNITION
LIGHTING INSTRUCTIONS
This appliance is equipped with a direct
spark ignition device. This device lights
the main burners each time the room
thermostat (closes) calls for heat. See
lighting instructions on the furnace.
During initial start-up, it is not unusual
for odor or smoke to come out of any
room registers. It is recommended to
ensure proper ventilation by opening
windows and doors, before initial firing.
The furnace has a negative pressure
switch that is a safety during a call for
heat. The induced draft blower must pull
a negative pressure on the heat
exchanger to close the negative
pressure switch. The induced draft
blower must maintain at least the
negative pressure switch set point for
the furnace to operate. If the induced
draft blower fails to close or maintain the
closing of the negative pressure switch,
a heat call would be prevented until the
problem is cleared.
TO START FURNACE
1. Remove the control access door.
2.
BE SURE THAT THE MANUAL GAS
CONTROL HAS BEEN IN THE
“OFF” POSITION FOR AT LEAST
FIVE MINUTES. DO NOT ATTEMPT
TO MANUALLY LIGHT THE MAIN
BURNERS. FAILURE TO FOLLOW
THIS WARNING CAN CAUSE A
FIRE OR AN EXPLOSION
RESULTING IN PROPERTY
DAMAGE, PERSONAL INJURY OR
DEATH.
3. Turn off the furnace electrical power
and set the room thermostat to the
lowest setting.
4. Turn the gas control knob to the “On”
position, or move the gas control
lever to the “On” position.
5. Replace the control access door.
6. Turn on the electrical power.
7. Set the room thermostat to a point
above room temperature to light the
main burners. After the burners are lit,
set room thermostat to a desired
temperature.
TO SHUT DOWN FURNACE
1. Set the room thermostat to off and its
lowest setting.
2. Turn manual gas stop to the closed
position.
3. Turn off the electrical power to the
furnace.
4. Remove burner compartment door.
5. Move the main gas valve knob or
lever to the off position.
6. Replace the burner compartment
door.
SHOULD OVERHEATING OCCUR OR
THE GAS SUPPLY FAIL TO SHUT
OFF, SHUT OFF THE MANUAL GAS
VALVE TO THE APPLIANCE BEFORE
SHUTTING OFF THE ELECTRICAL
SUPPLY. FAILURE TO DO SO CAN
CAUSE AN EXPLOSION OR FIRE
RESULTING IN PROPERTY DAMAGE,
PERSONAL INJURY OR DEATH.
IGNITOR PLACEMENT,
ALIGNMENT & LOCATION
Ignition failure may be a result of
improper ignitor alignment caused during
a service call or other work done to the
furnace in the field. When performing any
work on the burner, heat exchanger, etc.,
the technician must check alignment of
the spark ignitor. Misalignment of the
ignitor could cause a failure to light or
rough ignition. The correct ignitor
alignment is shown in Figure 44.
SEQUENCE OF OPERATION
See the section of this book titled
“Electrical Wiring - Thermostat” for a
wiring diagram showing how to connect a
thermostat.
SINGLE-STAGE HEAT
THERMOSTAT
NOTE:
Single-stage heat operation is
determined by the position of the
jumper at P7 on the control board.
Options are: 5 minutes between 1
st
and 2
nd
stage, or 12 minutes between
1
st
and 2
nd
stage (see Figure 45).
For single-stage operation, “W” from
the thermostat must be connected to
“W” on the furnace control.
Do not leave jumper at P7 in the
“NONE” position when using a single-
stage thermostat with the timed
staging feature. If the jumper is left on
“NONE”, the furnace will never reach
high heat (100% heat).
NOTE:
When
there is a low heat call present at the
time of ignition, this furnace will light
on high fire heat and immediately drop
to low fire as soon as flame is sensed.
This can sometimes appear to be
ignition on low heat stage but this is
not the case. Listen carefully to hear
the inducer and gas valve relays
switch to low fire after ignition when a
low heat call is present. If a high heat
call is present at the time of ignition,
both ignition and steady state heat will
occur at high fire and there will be no
change in operation after ignition.
a. Connect the “W” terminal on the
thermostat to the “W” terminal on
the control board.
b. When there is a call for heat, the
“R” and “W” contacts close and the
IFC runs a self check routine to
verify that the pressure switch
contacts are open. The limit switch
contacts are constantly monitored.
c. The induced draft motor starts on
high speed. After a 30 second pre-
purge, the spark ignitor energizes
and the high fire gas valve opens,
lighting the burners.
d. After the gas valve opens, the
remote flame sensor must prove
ignition for one second using the
process of flame rectification. If the
burners do not light, the system
!
WARNING
!
WARNING
FIGURE 44
UPFLOW OPTIMUM IGNITOR LOCATION
DOWNFLOW/HORIZONTAL OPTIMUM IGNITOR LOCATION