18-CD19D7-22
17
Installer’s Guide
▲
WARNING
!
FIRE OR EXPLOSION HAZARD
Failure to follow the safety warnings exactly could result in
serious injury, death or property damage.
Never test for gas leaks with an open flame. Use a com-
mercially available soap solution made specifically for the
detection of leaks to check all connections. A fire or
explosion may result causing property damage, personal
injury, or loss of life.
GAS PIPING
▲
WARNING
!
FIRE - EXPLOSION HAZARD
DO NOT RUN FLEXIBLE GAS LINE THROUGH THE FUR-
NACE CABINET WALL. FAILURE TO FOLLOW THIS WARN-
ING COULD RESULT IN PROPERTY DAMAGE, SERIOUS
PERSONAL INJURY, OR DEATH.
This unit is shipped standard for left side installation of gas
piping. A piping knockout is also provided in the right side for
an alternate piping arrangement. The installation of piping
shall be in accordance with piping codes and the regulations
of the local gas company. Pipe joint compound must be resis-
tant to the chemical reaction with liquefied petroleum gases.
Refer to piping Table 11 for delivery sizes.
NOTE: Refer to local codes and the National Fuel Gas
Code, current edition, for gas pipe requirements.
The furnace and its individual shut-off valve must be discon-
nected from the gas supply piping system during any pressure
testing of that system at test pressures in excess of 1/2 psig.
The furnace must be isolated from the gas supply piping by
closing its individual manual shut-off valve during any
pressure testing of the gas supply piping system at test
pressures equal to or less than 1/2 psig.
▲
CAUTION
!
Use a backup wrench on the gas valve when installing gas
piping to prevent damage to the gas valve and manifold
assembly.
NOTE: Maximum pressure to the gas valve for natural gas
is 13.8" W.C. Minimum pressure is 5.0" W.C. Maximum
pressure to the gas valve for propane is 13.8" W.C. Mini-
mum pressure is 11.0" W.C.
All gas fittings must be checked for leaks using a soapy solution
before lighting the furnace.
DO NOT CHECK WITH AN
OPEN FLAME!
The following warning complies with State of California law, Proposition 65.
Hazardous Gases!
Exposure to fuel substances or by-products of incomplete
fuel combustion is believed by the state of California to
cause cancer, birth defects, or other reproductive harm.
▲
WARNING
!
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 approx. 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 6 second ignition trial period.
After the flame sensor confirms that ignition has been
achieved, the delay fan ON period (fixed at 45 seconds)
begins timing. After the delay of 45 seconds, the indoor
blower motor will be energized and will continue to run
during the heating cycle.
TOP
V
IE
W
AUTOMATIC GAS
V
AL
V
E
W
ITH MA
N
UAL SHUTOFF
LEFT SIDE PIPING (STANDARD)
TOP VIEW OF RIGHT SIDE PIPING
RIGHT SIDE PIPING (OPTIONAL)
h
DRIP LEG
DRIP LEG
IMPORTANT:
A sediment trap must be installed in the gas line
before the furnace gas valve. The sediment trap
must be located as close to the furnace cabinet as
practical.
When the thermostat is satisfied, R and W thermostat
contacts 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
(fixed at 100 seconds), then will be de-energized by the control
module.
