36
18-CD29D1-11
Installer’s Guide
AIRFLOW ADJUSTMENT
Check inlet and outlet air temperatures to make sure they
are within the ranges specified on the furnace rating name-
plate. If the airflow needs to be increased or decreased, see
the wiring diagram for information on changing the speed
of the blower motor.
▲
WARNING
!
ELECTRICAL SHOCK HAZARD
Disconnect power to the unit before removing the blower
door.
Failure to follow this warning could result in property
damage, personal injury or death.
This unit is equipped with a blower door switch which cuts
power to the blower and gas valve causing shutdown when
the door is removed. Operation with the door removed or
ajar can permit the escape of dangerous fumes. All panels
must be securely closed at all times for safe operation of the
furnace.
INDOOR BLOWER TIMING
Heating: The integrated furnace control module controls
the indoor blower. The blower start is fixed at 45 seconds
after ignition (10 seconds for downflow models). The FAN-
OFF period is field selectable by dip switches at 60, 100,
140, or 180 seconds. The factory setting is 100 seconds (See
wiring diagram).
Cooling: The fan delay off period is factory set at 0 sec-
onds. The option for 80 second delay off is field selectable
(See wiring diagram).
ROOM AIR THERMOSTAT
HEAT ANTICIPATOR ADJUSTMENT
Set the thermostat heat anticipator according to the cur-
rent flow measured, or the settings found in the notes on
the furnace wiring diagram (found in the SERVICE FACTS
or inside the furnace casing).
INSTRUCTIONS TO THE OWNERS
▲
WARNING
!
EXPLOSION HAZARD
In the event that electrical, fuel, or mechanical fail-
ures occur, shut off the gas supply off at the manual
gas valve, located on the supply gas piping coming
into the furnace, before turning off the electrical
power to the furnace. Contact the service agency
designated by your dealer.
BURNER BOX TEMPERATURE LIMIT DEVICE
All models are equipped with a manual reset temperature
limit located on the burner box. In case of excessive tem-
perature, the limit will open and cause the circuit to open
which shuts off all flow of gas.
To shut off.
For complete shut-down: Flip the switch on the main gas
valve to the “OFF” position, (See Figure 57 & 58). Discon-
nect the electrical supply to the unit.
▲
CAUTION
!
If this is done during the cold weather months, provisions
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 weath-
er. If for any reason your furnace should fail to oper-
ate damage could result, such as frozen water pipes.
SEQUENCE OF OPERATION
Thermostat call for heat
R and W thermostat contacts close signaling the control
module to run its self-check routine. After the control mod-
ule has verified that the pressure switch contacts are open
and the limit switch(es) contacts are closed, the draft blow-
er will be energized.
As the induced draft blower comes up to speed, the pressure
switch contacts will close and the ignitor warm up period
will begin. The ignitor will heat for approximately 20 sec-
onds, then the gas valve is energized to permit gas flow to
the burners. The flame sensor confirms that ignition has
been achieved.
After the flame sensor confirms within a 4 second trial pe-
riod 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 (downflow models have a 10 second
blower ON delay).
When the thermostat is satisfied,
R and W thermostat con-
tacts open, the gas valve will close, the flames will extin-
guish, and the induced draft blower will be de-energized.
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 tem-
perature to bring on the gas valve. Restrict the airflow by
blocking the return air (disconnecting the indoor blower
may trip the inducer limit).
When the furnace reaches the maximum outlet tempera-
ture as shown on the rating plate, the burners must shut
off. If they do not shut off after a reason able time and over-
heating is evident, a faulty limit switch is probable and the
limit switch must be replaced. After checking the operation
of the limit control, be sure to remove the paper or card-
board from the return air inlet. Refer to Service Facts for
additional instructions.
NOTE TO INSTALLER
Review the following warnings with the owner. Review con-
tents of USER’S INFORMATION MANUAL with the own-
er.
