34 18-CD33D1-4
Installer’s Guide
LIGHTING INSTRUCTIONS
SAFETY HAZARD
DO NOT attempt to manually light the burner.
Failure to follow this warning could result in property
damage, personal injury or death.
Lighting instructions appear on each unit. Each instal-
lation must be checked out at the time of initial start up
to insure proper operation of all components. Check out
should include putting the unit through one complete cy-
cle as outlined below.
Turn on the main electrical supply and set the thermostat
above the indicated temperature. The ignitor will auto-
matically heat, then the gas valve is energized to permit
the flow of gas to the burners. After ignition and flame is
established, the flame control module monitors the flame
and supplies power to the gas valve until the thermostat
is satisfied.
To shut off.
For complete shut-down: Flip the switch on the main gas
valve to the “OFF” position, (See Figure 53 & 54). Discon-
nect the electrical supply to the unit.
If this is done during the cold weather months, provi-
sions must be taken to prevent freeze-up of all water
pipes and water receptacles.
Failure to follow this warning could result in property
damage.
Whenever your house is to be vacant, arrange to
have someone inspect your house for proper temper-
ature. This is very important during freezing weather.
If for any reason your furnace should fail to operate
damage could result, such as frozen water pipes.
SEQUENCE OF OPERATION
Thermostat call for heat
R and W thermostat contacts close signaling the con-
trol module to run its self-check routine. After the control
module has verified that the pressure switch contacts are
open and the limit switch(es) contacts are closed, the
draft blower will be energized.
As the induced draft blower comes up to speed, the pres-
sure switch contacts will close and the ignitor warm up
period will begin. The ignitor will heat for approximately
20 seconds, then the gas valve is energized to permit gas
flow to the burners. The flame sensor confirms that igni-
tion has been achieved.
After the flame sensor confirms within a 4 second trial
period that ignition has been achieved, the delay to fan
ON period begins timing. After approximately 45 seconds
the indoor blower motor will be energized and continue to
run during the heating cycle.
When the thermostat is satisfied, R and W thermostat
contacts open, the gas valve will close, the flames will
extinguish, and the induced draft blower will be de-en-
ergized. The indoor blower motor will continue to run for
the fan off period (Field selectable at 60, 100, 140 or 180
seconds), then be de-energized by the control module.
CONTROL AND SAFETY SWITCH ADJUSTMENTS
LIMIT SWITCH CHECK OUT
The limit switch is a safety device designed to close the
gas valve should the furnace become overheated. Since
proper operation of this switch is important to the safety
of the unit, it must be checked out on initial start up by
the installer.
To check for proper operation of the limit switches, set
the thermostat to a temperature higher than the indicated
temperature to bring on the gas valve. Restrict the airflow
by blocking the return air (disconnecting the indoor blow-
er may trip the inducer limit). When the furnace reaches
the maximum outlet temperature as shown on the rating
plate, the burners must shut off. If they do not shut off af-
ter a reason able time and overheating is evident, a faulty
limit switch is probable and the limit switch must be re-
placed. After checking the operation of the limit control,
be sure to remove the paper or cardboard from the return
air inlet. Refer to Service Facts for additional instructions.
NOTE TO INSTALLER
Review the following warnings with the owner. Review
contents of USER’S INFORMATION MANUAL with the
owner.
R
White-Rodgers 36J gas valve
Outlet Pressure Boss
Regulator
Adjustment
Inlet Pressure
Boss (opt.)
On/Off Switch
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