MG3P Installation Manual

26
6. Disconnect the wires from the terminals.
7. Remove the supply gas piping from the gas valve inlet.
8. Remove four screws securing the gas manifold assembly to
the burner assembly.
9. Set aside the screws and remove the gas manifold assembly
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 from the gas manifold
assembly.
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 into the
gas manifold assembly by hand until snug, then tighten
with a wrench.
12. Install the appropriate LP/Propane orifices into the gas
manifold assembly.
MG3P MODELS ONLY:
a.) Remove the pressure regulator cap (Figure 36) from the
gas valve.
b.) 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.
c.) Replace the cap and tighten firmly.
MG3S MODELS ONLY:
IMPORTANT NOTES:
• When converting to LP/Propane gas from natural gas, the
springs from gas valve must be replaced by the larger
springs from the kit. The LP/Propane springs for both
HIGH & LOW fire are the same size, shape and color.
• Use only a Torx-25 (included with this kit) or 3/16” flathead
screwdriver when removing adjustment screws or during
pressure adjustment.
a.) Remove the HIGH fire cap screw. See Figure 2 (page 3).
b.) Remove and discard the HIGH fire adjustment screw
from the gas valve.
c.) Remove the spring from the gas valve and discard.
d.) Install a larger spring from the conversion kit.
e.) Install a new adjusting screw from the kit.
IN
ON
OFF
Inlet
Pressure
Ta p
Inlet
Pressure
Ta p
Manifold
Pressure
Ta p
Manifold
Pressure
Ta p
2-STAGE GAS VALVES
Model VR8205Q2381
Model VR9205Q1028
ON / OFF
Knob
ON / OFF
Switch
HI Input
Adjusting
Screw
Lo Input
Adjusting
Screw
HI Input
Adjusting
Screw
Lo Input
Adjusting
Screw
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
SINGLE STAGE GAS VALV E
Figure 36. Gas Valve - Top View
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 Figure
37 (page 27).
5. Turn the gas valve ON/OFF knob to the OFF position.
CAUTION:
It is good practice to label all wires prior to
disconnection. Wiring errors can cause improper
and dangerous operation.