28
Removing The Burner Orifices
1. Adjust the thermostat to the OFF position, or its lowest
temperature setting.
2. Turn the main gas supply valve (on the outside of the
unit) to the OFF position.
3. Turn off all electrical power to the furnace.
4. Remove the door from the burner compartment. See
5. Turn the gas valve ON/OFF knob (1) to the OFF position.
CAUTION:
It is good practice to label all wires prior
to disconnection. Wiring errors can cause
improper and dangerous operation.
6. Disconnect the wires from the terminals (2).
7. Remove the supply gas piping from the gas valve inlet
(3).
8. Remove four screws (4) securing the gas manifold
assembly (5) to the burner assembly (6).
9. Set aside the screws (4) and remove the gas manifold
assembly (5) from the burner assembly.
WARNING:
Do not attempt to drill the gas orifices. Use only
factory supplied orifices. Improperly drilled
orifices may cause fire, explosion, carbon
monoxide poisoning, personal injury or death.
10. Carefully remove the burner orifices (7) from the gas
manifold assembly (5).
11.
Read the rating plate affixed to the appliance to
determine its rated input (Btu/hr) and the size of the
factory installed orifices. NOTE: Natural Gas furnaces
may be equipped with one of three orifices.
WARNING:
Do not use Teflon tape or pipe joint compound
on the orifice threads. The hole in the orifice
may become blocked and cause fire, explosion,
property damage, carbon monoxide poisoning,
personal injury, or death.
IMPORTANT NOTES:
• Before installing an orifice, check the face or side
of the orifice for the drill number to ensure that it
is the appropriate size.
• To prevent cross threading, screw the orifices (7)
into the gas manifold assembly (5) by hand until
snug, then tighten with a wrench.
12. Install the appropriate LP/Propane orifices (7) into the
gas manifold assembly (5).
13. Remove the pressure regulator cap (
) from
the gas valve.
Conversion to LP/Propane
WARNING:
This furnace was shipped from the factory
equipped to operate on natural gas. Conversion
to LP/propane gas must be performed by
qualified service personnel using factory
supplied conversion parts. Failure to use the
proper conversion kit can cause fire, explosion,
property damage, carbon monoxide poisoning,
personal injury, or death.
This furnace can be converted from factory-equipped
natural gas to Liquid Propane gas. Conversion of this
valve requires replacement of the burner orifices on the
manifold assembly and flipping the regulator cap to the
side marked LP. See
below. The orifices required
for conversion are supplied with the furnace.
For altitudes between 0 and 1,999 feet, only the orifice is
changed. Altitudes between 2,000 and 10,000 feet require
both the orifice and regulator pressure to be changed.
See
to determine the correct orifice
size and manifold pressure to use at different altitudes.
WARNING:
Shut off the gas supply at the manual gas shutoff
valve, before disconnecting the electrical power.
A fire or explosion may result causing property
damage, personal injury or loss of life. Failure to
follow the safety warnings exactly could result
in serious injury, death or property damage.
WARNING:
To avoid electric shock, personal injury, or death,
turn off the electric power at the disconnect
or the main service panel before making any
electrical connections.
Figure 36
ON
OFF
IN
N
A
T N
A
T
L
P
L
P
Other side
of cap
Pressure Regulator
Cap
Manifold
Pressure Plug
Inlet Pressure
Plug
ON/OFF
Knob
OR
Figure 36.
Gas Valve - Top View
Summary of Contents for M4RC-072D-35C
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