34
18-CD19D8-18
Installer’s Guide
▲
CAUTION
!
Replace and/or tighten all plugs removed or loosened
when adjusting gas pressure. Leak check the fittings
before placing the furnace into regular service. Failure
to follow this warning could result in fire, explosion, or
property damage.
Table 17 lists the main burner orifices used with the furnace.
If a change of orifices is required to correct the furnace input
rating refer to Table 18.
REINSTALLATION OF THE BURNER BOX COVER
Figure 55 shows the correct way to reinstall the burner box
cover if adjustment or replacement of the flame sensor, hot
surface igniter, or main burner orifices have required removal
of the cover.
START-UP AND ADJUSTMENT
PRELIMINARY INSPECTIONS
▲
WARNING
!
Disconnect power to the unit before removing the blower
door. Allow a minimum of 10 seconds for IFC power supply
to drain to 0 volts. Failure to follow this warning could
result in property damage, personal injury or death.
With gas and electrical power “OFF”
1. Duct connections are properly sealed
2. Filters are in place
3. Venting is properly assembled
4. Blower door is in place
Turn the main gas valve toggle switch (See Figures 53 & 54)
within the unit to the “
OFF
” position. Turn the external gas
valve to “ON”. Purge the air from the gas lines. After purging,
check all gas connections for leaks with a soapy solution —
DO
NOT CHECK WITH AN OPEN FLAME.
Allow 5 minutes
for any gas that might have escaped to dissipate.
LP Gas being heavier than air may require forced ventilation.
Turn the toggle switch on the gas valve in the unit to the
“ON” position.
LIGHTING INSTRUCTIONS
▲
WARNING
!
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 installation
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 cycle as outlined below.
Turn on the main electrical supply and set the thermostat
above the indicated temperature. The ignitor will automati-
cally 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 shutdown: Turn the gas cock knob on the main
gas valve to the “OFF” position (See Figure 49). 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.
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 dam-
age could result, such as frozen water pipes.
SEQUENCE OF OPERATION
Thermostat call for heat (2-stage thermostat)
Call for 1st stage only:
W1 thermostat contacts close signaling the control module to
run its self-check routine. After the control module has
verified that the 1st stage 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 in 1st stage to permit gas flow to the
burners.
The flame sensor confirms that ignition has been achieved
within the 4 second ignition trial period.
As the flame sensor confirms that ignition has been achieved,
the delay to fan ON period begins timing and after approx.
45 seconds the indoor blower motor will be energized at low
speed and will continue to run during the heating cycle.
Call for 2nd stage after 1st stage:
W2 thermostat contacts close signaling a call for 2nd stage
heat. After a 30 second delay, the induced draft blower will
be energized on high speed and the 2nd stage pressure
switch contacts will close. The gas valve is energized in 2nd
stage and the indoor blower motor in high speed.
2nd stage satisfied, 1st stage still called:
W2 thermostat contacts open signaling that 2nd stage
heating requirements are satisfied.
The induced draft blower is reduced to low speed allowing
the 2nd stage pressure switch contacts to open and the gas
valve is reduced to 1st stage. The indoor blower motor is
reduced to low speed.
1st stage satisfied:
W1 thermostat contacts open signaling that 1st stage
heating requirements are satisfied. The gas valve will close
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.
▲
WARNING
!
EXPLOSION HAZARD!
PROPANE GAS IS HEAVIER THAN AIR AND MAY COL-
LECT IN ANY LOW AREAS OR CONFINED SPACES. IN
ADDITION, ODORANT FADE MAY MAKE THE GAS
UNDETECTABLE EXCEPT WITH A WARNING DEVICE. IF
THE GAS FURNACE IS INSTALLED IN A BASEMENT, AN
EXCAVATED AREA OR A CONFINED SPACE, IT IS
STRONGLY RECOMMENDED TO CONTACT A GAS
SUPPLIER TO INSTALL A GAS DETECTING WARNING
DEVICE IN CASE OF A GAS LEAK
.
NOTE:
The manufacturer of your furnace does NOT test any
detectors and makes no representations regarding any
brand or type of detector.
