40
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 “no heat call” would result.
TO START FURNACE
1. BE SURE THAT THE MANUAL GAS
STOP 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.
2. Set the room thermostat to the lowest
setting.
3. Remove furnace panel.
4. Turn the gas control knob to the “ON”
position, or set the gas control switch
to the “ON” position.
5. Securely replace furnace panel.
6. Turn on the manual gas stop and the
electrical power.
7. Set the room thermostat to “Heat” and
adjust to desired room temperature.
8. Complete installation checklist.
SHOULD OVERHEATING OCCUR OR
THE GAS SUPPLY FAIL TO SHUT
OFF, SHUT OFF THE MANUAL GAS
STOP 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 35.
Sequence of operation with a single
stage thermostat
a. Connect the “W” terminal on the
thermostat to the W2 terminal on the
IFC. Do not connect any wire to “W”
on IFC when using a single-stage
thermostat.
b. When there is a call for heat, the “R”
and “W2” contacts close and the IFC
runs a self check routine to verify that
both of the pressure switch contacts
are open. The limit switch contacts
are constantly monitored.
c. The induced draft motor starts on high
until the low and high pressure switch
contacts close (a maximum of 60
seconds), and then runs for a 30-
second pre-purge. After the 30-
second pre-purge, the spark ignitor
energizes and the high stage of
the gas valve opens, lighting the
burners.
d. After the gas valve energizes, the
remote flame sensor must prove
ignition for one second using the
process of flame rectification. If the
burners do not light or flame is not
sensed, the system goes through
another ignition sequence. It does
this up to 4 times.
e. The IBM starts on low speed 20
seconds after the burners light and
flame is sensed. The induced draft
motor and gas valve switch to low
speed. The furnace operates on
low fire for 12 minutes and then, if
the thermostat is not satisfied,
shifts to high fire, causing the draft
inducer to go to high speed, the
gas valve to 100% and the main
blower goes to high-fire heating
speed.
f. When the thermostat cycle ends,
the gas valve de-energizes, and
the burners go out.
g. The draft inducer will continue
running for a 10 second post
purge.
h. The main blower will run for for the
user-defined blower-off delay (this
timing is field adjustable, for 90,
120 150, or 180 seconds). See
Figure 36 for switch settings.
Sequence if the system doesn’t
light or doesn’t sense flame:
a. If flame is not sensed within 8
seconds after the gas valve
energizes, the valve and the ignitor
are de-energized. The induced
draft motor will, stop momentarily,
and then restart to check PS
operation.
b. The ignition process goes through
three more tries.
c. If there is no ignition after the
fourth trial, the furnace goes into
soft lockout for one hour.
d. The sequence repeats after a one
hour delay and continues
repeating until ignition is
successful or the call for heat is
terminated.
e. To reset the lockout, break power
either at the thermostat or at the
unit disconnect switch for 30
seconds. The furnace will then go
through another set of trials for
ignition.
!
WARNING
!
WARNING
FIGURE 34
UPFLOW OPTIMUM IGNITOR LOCATION
