Unit installation

035-20507-001 Rev. A (0804)
2 Unitary Products Group
FURNACE CONVERSION
1. Remove the upper access door. On 90+ AFUE units,
remove the burner box cover.
2. Carefully remove the wires from the gas valve and note
their location so they may be properly replaced. Remove
the screws that hold the manifold to the manifold bracket
and slide the manifold off the burners. On 90+ AFUE
units, the manifold is retained by two screws at the bot-
tom and hooks in at the top of the burner box.
3. Remove the main burner orifices from the manifold and
retain for future use.
4. Install the propane main burner orifices in the manifold
and tighten them. After installing a propane orifice in
each location, any leftover orifices may be discarded.
5. Reinstall the manifold in the assembly by reversing the
removal process.
6. Reconnect the wires to the proper terminals on the gas
valve.
7. When installing gas piping on 80% AFUE units, insert
tapped gas pipe nipple (supplied with kit) into inlet fitting
of gas valve. If using the right side cabinet knock out, the
nipple can be either be installed before or after making
the u-bend. On 90% AFUE units, install an elbow into the
inlet fitting on the gas valve and then install the tapped
gas pipe nipple.
8. Install (thread) the gas line pressure switch (supplied
with kit) into the 1/8 NPT tapped hole in nipple applying
pipe dope to the switch fitting prior to installation. Tighten
the switch making sure the connection does not leak.
NOTE: The gas line pressure switch will cause the furnace to
lock out if the gas supply pressure drops below 6” w.c. The
ignition control will display a fault code 7 and will reset after
one hour.
9. Disconnect the purple wire from the flame sensor.
10. Using the appropriate wire harness (supplied with kit)
connect the purple wire from the flame sensor into the
insulated male connector; connect the two 1/4” insulated
terminals to the pressure switch; and connect the
remaining insulated terminal to the flame sensor.
11. Replace the gas valve regulator spring using the instruc-
tion sheet packed in the envelope with the spring.
12. Install the propane gas conversion label as described in
the labels section of this instruction.
13. Refer to the unit installation instructions to complete the
installation before continuing with these procedures.
ORIFICE SIZE SELECTION
A number of factors determine the correct orifice usage for
your application. These factors include the original orifice siz-
ing, BTU content of the gas and the altitude.
For natural gas applications, contact your gas supplier for the
actual BTU content (heating value) of the fuel provided at
your altitude.
Use the BTU heating value that is nearest to your value.
Read across the selected table from the standard orifice to
the altitude for your application and note the new orifice size.
For propane (LP) applications, Use Table 1 for burner orifice
part numbers. Use Table 2 to select the proper high altitude
orifice size.
EXAMPLE: If your unit has a #56 orifice, as standard for pro-
pane, and a heating gas value of 2516 BTU/CU.FT., at an alti-
tude of 7,000 feet, a #58 orifice will provide the correct firing
rate.
The gas supply shall be shut off prior to disconnect-
ing the electrical power, before proceeding with the
conversion.
Table 1: Orifice Part Numbers
BURNER ORIFICES
Size # Source 1 Part Number
Blank 029-20423-000
41 029-20423-041
42 029-20423-042
43 029-24243-043
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