26
h. Remove four screws (4) securing the gas manifold
assembly (5) to the burner assembly (6).
i. Set aside the screws (4) and remove the gas manifold
assembly (5) from the burner assembly.
j. Carefully remove the burner orifi ces (7) from the
gas manifold assembly (5).
WARNING:
Do not attempt to drill the gas orifi ces. Use
only factory supplied orifices. Improperly
drilled orifi ces may cause fi re, explosion,
carbon monoxide poisoning, personal injury
or death.
k. Read the rating plate affi xed to the appliance to
determine its rated input (Btu/hr) and the size of
the factory installed orifi ces.
NOTE:
Natural Gas
furnaces may be equipped with one of three orifi ces.
WARNING:
Do not use Tefl on tape or pipe joint compound
on the orifi ce threads. The hole in the orifi ce
may become blocked and cause fi re, explosion,
property damage, carbon monoxide poisoning,
personal injury, or death.
IMPORTANT NOTES:
Before installing an orifi ce, check the face or side of
the orifi ce for the drill number to ensure that it is the
appropriate size.
To prevent cross threading, screw the orifi ces (7) into
the gas manifold assembly (5) by hand until snug,
then tighten with a wrench.
l. Install the appropriate LP/Propane orifi ces (7) into
the gas manifold assembly (5).
m. Remove the pressure regulator cap (Figure 35) from
the gas valve.
n. Invert the cap so that the letters facing up represent
the type of gas being used for the furnace.
NOTE:
The cap is marked NAT on one end for
natural gas and LP on the other end for propane.
If converting to LP propane, make sure the LP end
is facing up when installed.
o. Replace the cap and tighten fi rmly.
p. Install the gas manifold assembly (5) back into the
burner assembly (6). Make sure the center of the
orifi ces are aligned with center of the burners.
q. Secure the manifold assembly (5) to the burner
assembly (6) with the four screws (4), removed in
step 1-h.
r. Reconnect the gas piping to the gas valve inlet (3).
ON
OFF
IN
N
AT NA
T
LP LP
Other side
of cap
Pressure Regulator
Cap
Manifold
Pressure Plug
Inlet Pressure
Plug
ON/OFF
Knob
OR
Figure 35. Gas Valve - Top View
s. Reconnect the wires to the gas valve terminals (2).
2. Measure the Supply Gas Pressure:
IMPORTANT NOTE: To obtain an accurate pressure
reading, turn off all gas appliances (i.e. Dryers, water
heaters, stoves, etc.) at their ON/OFF control or
individual gas valves.
a. Remove the inlet pressure plug (Figure 35) from
the INLET side of the gas valve with a 3/16 Allen
wrench.
b. Install a 1/8 NPT fi tting, which is compatible with a
manometer or similar pressure gauge.
c. Connect the manometer or pressure gauge to the
inlet pressure tap.
d. Turn on all electrical power to the furnace.
e. Turn the main gas supply valve (on the outside of
the unit) to the ON position.
f. Start the furnace by adjusting the thermostat to
it’s highest setting. Allow the furnace to run for 10
minutes.
g. Check the incoming gas line pressure. Propane gas
furnaces must be between 11.0”-14.0” W.C. Natural
gas installations must be between 4.5”-10.0” W.C. If
the pressure is not between these specifi ed ranges,
contact your local gas supplier for adjustment.
h. Adjust the thermostat to it’s lowest setting and allow
the unit to cycle off.
i. Turn the main gas supply valve (on the outside of
the unit) to the OFF position.
j. Turn off all electrical power to the furnace.
k. Disconnect the manometer or pressure gauge.
l. Remove the NPT fi tting and reinstall the inlet
pressure plug.
NOTE:
To prevent cross threading,
hand tighten the plug fi rst, then tighten with 3/16
Allen wrench.
