Trane *DC040C924 Installer'S Manual Download Page 23

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18-CD19D5-10

Installer’s Guide

To shut off.

For complete shutdown: Flip the switch on the main gas valve to
the “OFF” position (See Figures 32 & 33). Disconnect 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 temperature.
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 control 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 pressure
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 ignition has been achieved within the
4 second ignition trial period.

After the flame sensor confirms that ignition has been achieved,
the delay to fan ON period begins timing and after approxi-
mately 45 seconds the indoor blower motor will be energized and
will 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-energized. The indoor blower
motor will continue to run for the fan off period (Field selectable
at 60, 100, 140 or 180 seconds), then will 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 thermo-
stat 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 blower 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 after a reasonable 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.

AIRFLOW ADJUSTMENT

Check inlet and outlet air temperatures to make sure they are
within the ranges specified on the furnace rating nameplate.
If the airflow needs to be increased or decreased, see the
wiring diagram for information on changing the speed of the
blower motor.

▲

WARNING

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 controls the indoor
blower. The blower start is fixed at 45 seconds after ignition.
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 seconds.
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 current flow
measured, or the settings found in the notes on the furnace
wiring diagram (found in the SERVICE FACTS or inside the
furnace casing).

On/Off Switch

Outlet Pressure Boss

On/Off

ff Swi

Switch

Inlet Pressure

let Pressure

Boss

Boss (opt.)

Regul

ulator

tor