Failure to follow this warning could result in personal
injury, or death.
Blower access door switch
control. No component
can occur unless
manually closing this switch for service purposes.
3. To Begin Component
Remove blower ac-
cess door. Disconnect the thermostat
R lead from the
furnace control board. Manually close the blower door
switch. Short (jumper) the C terminal on control to the
quick connect terminal on con-
trol until LED goes out (approximately
2 sec). Gas
will not be turned
The furnace control allows all components,
the gas valve, to be run for short period of time. This feature
helps diagnose a system problem in case of a component
thermostat signal is present at the control.
Component test sequence is as follows:
Refer to service label attached to furnace or see Figure 44.
a. LED will display previous status code 4 times.
If no previous code is present, go directly to b.
b. Inducer motor starts and continues to run until Step
f of component test sequence.
c. Hot surface igniter is energized for 15 sec., then off.
d. Blower motor operates on HEAT speed for 10 sec.
e. Blower motor operates on COOL speed for 10 sec.
f. Inducer motor stops.
g. Reconnect R lead to furnace control board, release
blower door switch and re-install blower door.
4. Operate furnace per instruction on door.
5. Verify furnace shut down by lowering thermostat setting
below room temperature.
6. Verify furnace
restarts by raising thermostat
above room temperature.
Derate Multiplier for U.S.A.
* Derate multiplier factors are based on midpoint
altitude for altitude ran( e.
Failure to follow this warning could result in injury,
death and/or property damage.
DO NOT bottom
out gas valve regulator
FURNACE DAMAGE HAZARD
Failure to follow this caution may result in reduced
out-of round holes, etc.) can cause excessive burner
noise and misdirection
of burner flames.
causing failures. (See Figure 42)
Furnace gas input rate on rating plate is for installations at
altitudes up to 2000 ft. (610 M).
Furnace input rate must be
within +/-2 percent of furnace rating plate input.
1. Determine the correct gas input rate.
The input rating for altitudes above 2,000 ft. (610 M)
must be reduced by 4 percent for each 1,000 ft. (305
M) above sea level. For installations
below 2000 ft.,
refer to the unit rating plate. For installations
2000 ft. (610 M), multiply the input on the rating plate
by the derate multiplier in Table 11 for the correct input
2. Determine the correct orifice and manifold pressure ad-
justment. There are two different orifice and manifold
tables. All models in all positions, except
Low NOx models in downflow or horizontal positions,
use Table 15 (22,000 Btuh/Burner).
Low NOx models in the downflow
or horizontal posi-
tions must use Table 16 (21,000 Btuh/Burner).
put listed on rating plate.
a. Obtain average yearly gas heat value (at installed
altitude) from local gas supplier.
b. Obtain average yearly gas specific gravity from loc-
al gas supplier.
c. Find installation altitude in Table 15 or 16.
d. Find closest natural gas heat value and specific
gravity in Table 15 or 16.
e. Follow heat value and specific gravity lines to point
of intersection to find orifice size and manifold pres-
sure settings for proper operation.
f. Check and verify burner orifice size in furnace.
NEVER ASSUME ORIFICE SIZE. ALWAYS CHECK
g. Replace orifice with correct size if required by Table
15 or 16. Use only factory-supplied
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