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Conversion
Conversion of this furnace to use LP/propane
gas must be made by qualified service
personnel, using only approved parts.
IMPORTANT NOTE: When converting a low
NOx furnace from Natural Gas to LP/Propane
Gas, it is necessary to remove the NOx
baffles from the furnace.
HIGH ALTITUDE CONVERSION
High Altitude Application
Conversion of this furnace to replace the pressure
switch or to utilize LP/propane gas must be made
by qualified service personnel, using factory
authorized or approved parts. High altitude
applications with this furnace can be field
performed by a simple adjustment of manifold
pressure, and if necessary changing the orifices
and the vent pressure switch. The changes
required depend on the installation altitude and
the heating value of the gas. The gas heating
value based on sea level can be obtained from
your local gas utility. The heating value of gas
at high altitude is always lower than the sea level
heating value. The heating values used in Tables
7 & 8 are based on sea level values.
Pressure Switch Conversion for
High Altitude Applications
These units are factory equipped to operate
between zero and 8000 feet above sea level. For
higher altitude applications, you may need to
replace the vent pressure switch in addition to the
main gas burner orifices. The approved high
altitude pressure switch kit is 903852.
directions to convert the furnace are given below:
1. READ ALL INSTRUCTIONS BEFORE
PROCEEDING WITH THE CONVERSION.
2. Disconnect all electrical power to the fur-
nace.
Field Supplied
Fused Service
Panel
Black (Hot)
White (Neutral)
Green or Bare
(Ground)
28
The
Field Supplied
Panel Connector
Black
Black
White
White
Ground
Ground
Field Supplied Disconnect
Within Sight of Furnace
Figure 25. Line Voltage Field Wiring
3. Remove the access door(s) from the front
of the unit.
4. Turn the gas valve knob to the OFF posi-
tion.
5. Shut off the gas to the unit.
6. The vent pressure switch will be replaced
(see Figure 30). This pressure switch is the
differential pressure switch between the
burner box and the vent assembly.
necessary, mark the two hoses that attach
to the pressure switch.
7. Disconnect the electrical leads to the pres-
sure switch. It is not necessary to mark the
electrical leads as polarity does not matter
across the switch.
8. Remove both hoses from the pressure
switch and remove the fasteners that se-
cure the pressure switch to the panel.
9. Discard the old pressure switch.
10. From the kit, install the new high altitude
pressure switch using the same fasteners
that were removed earlier.
11. Reattach the hoses to the pressure switch
ports in the same manner as they were
removed.
12. Reattach the electrical leads to the pres-
sure switch.
13. Turn on the electrical power to the furnace.
14. Turn the gas valve knob to the ON position.
15. Follow the start-up procedure outlined later
in these installation instructions. Verify that
the furnace is operating properly after the
conversion.
Natural Gas High Altitude
Conversion
All factory shipped furnaces are ready to operate
between zero and 4999 ft. above sea level. For
higher altitudes (between 5000 and 10,000 ft.
Black
White
Ground
Junction Box (may be internal
or external to the furnace). These
connections can be made in the
field supplied disconnect at the
furnace.
If
Field Line Voltage
Wiring
Factory Line
Voltage Wiring
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