4. Reinstall the main burners in the assembly by reversing
the removal process.
5. Install the high altitude conversion labels as described in
the LABELS sections of this instruction.
6. Refer to the unit installation instructions to complete the
installation before continuing with these procedures.
TESTS AND ADJUSTMENTS
The following tests must be performed at the time of conversion
following completion of the installation.
WARNING: Make sure both gas and power supplies
are shut off before proceeding.
1. Connect a manometer to the pressure tap on both the inlet
and the outlet side of the gas valve. Connect a power
supply and a gas supply to the unit, if not already con-
nected.
CAUTION: On 90+ AFUE models, refer to unit instal-
lation instructions for proper procedure for connecting
manometer to furnace.
2. Turn on the gas supply and bleed air from the gas supply lines
at a point as close to the inlet or the gas valve as is practical.
WARNING: Make sure the space is free of gas
before proceeding.
3. Turn the gas valve control knob to the ON position.
4. Make sure unit electrical disconnect switch is in the OFF
position.
5. Set the room thermostat to call for heat.
6. Turn unit electrical disconnect switch to ON. The combus-
tion blower should start and the hot surface igniter should
start glowing.
7. After air has been purged from the gas supply line, ignition
should occur. Shortly after ignition, the manifold and gas
inlet pressures can be checked on the manometers. Main
burner ignition may be delayed on the first ignition cycle
due to air in the gas manifold.
8. Adjust manifold pressure to the specifications shown in
Table 6. This setting will result in an input which is properly
derated for your altitude. Supply gas must be within the
range shown in Table 6. If required, adjust the incoming
regulator spring so that the pressure falls within the range.
WARNING: On 90+ AFUE furnaces, the gas valve
regulator cap must be in place to determine final gas
pressure setting.
9. Observe several ignition cycles. All main burners must
ignite without delayed ignition or burning at the orifices. If
delayed ignition is observed, verify that the igniter is prop-
erly mounted (not loose or crooked on bracket, and that
bracket screws are not loose).
10. If burning at the orifices, excessive yellow tipping, or
excessive noise is observed during any phase of main
burner operation, verify unit operation.
11. With the main burners ignited, check for gas leaks, espe-
cially in the following locations: gas valve inlet and outlet
connections, manifold union in the burner compartment,
and main burner orifices where they thread into the mani-
fold. Repair any leaks found and recheck.
WARNING: Do not use an open flame or any source
of ignition to check for leaks.
12. Operate the furnace for 15 minutes and measure the
supply and return air temperatures. Verify that the tem-
perature rise (supply air - return air rise) is within the
allowable range. See the unit data plate for the mini-
mum/maximum allowable temperature rise. If the meas-
ured rise is in excess of the maximum shown on the data
plate, a higher blower speed must be selected. See the
unit wiring diagram to make this change.
Burner Orifices
Size #
Source 1 Part Number
Blank
029 - 20423 - 000
41
029 - 20423 - 041
42
029 - 20423 - 042
43
029 - 20423 - 043
44
029 - 20423 - 044
45
029 - 20423 - 045
46
029 - 20423 - 046
47
029 - 20423 - 047
48
029 - 20423 - 048
49
029 - 20423 - 049
50
029 - 20423 - 050
51
029 - 20423 - 051
52
029 - 20423 - 052
55
029 - 20423 - 055
56
029 - 20423 - 056
57
029 - 20423 - 057
58
029 - 20423 - 058
59
029 - 20423 - 059
60
029 - 20423 - 060
NATURAL GAS
PROPANE (LP) GAS
TABLE 6 - GAS PRESSURES
TABLE 5 - ORIFICE PART NUMBERS
INLET GAS PRESSURE MUST BE
AT 4.5"-13.8" WC AT FURNACE.
SET MANIFOLD PRESSURE AT 1.6" WC FOR LOW FIRE
SET MANIFOLD PRESSURE AT 3.5" WC FOR HIGH FIRE
INLET GAS PRESSURE MUST BE
AT 11-13.8" WC AT FURNACE.
SET MANIFOLD PRESSURE AT 5.5" WC FOR LOW FIRE
SET MANIFOLD PRESSURE AT 10" WC FOR HIGH FIRE
650.78-N2.1V
Unitary Products Group
3
