Burner Orifi Ce Removal / Replacement - A.O. Smith 12 40GPC T 100 Service Handbook

Important: Use only factory authorized replacement
parts. If you lack the necessary skills to properly
perform the installation, you should not proceed, but
get help from a qualified service technician.
Tools required: 3/4" Open-End Wrench or Crescent
Wrench, Phillips Head Screwdriver, Ratchet with 1/4"
socket or 1/4" Nut Driver, Ratchet with 1/2" socket.
Removing the Inner Door/Manifold/Burner Assembly:
1. Set the gas control valve/thermostat to its lowest
setting by pressing the "COOLER" and "HOTTER"
buttons together at the same time holding for 1
second. Then press the "COOLER" button to the
lowest setting (Figure 102).
2. Turn gas control switch to the "OFF" position
(located right side of the gas control valve/
thermostat) and turn off the gas supply to the unit
(Figure 103).
3. Disconnect the electric connection by unplugging
the transformer from the wall outlet (Figure 103).
4. Remove the manifold cover/outer door from the
unit by depressing on the lower portion and pulling
outward.
5. Unplug all the electrical connections from the
bottom of the gas control valve/thermostat
(Figure 104).
6. Disconnect the electrical flag terminals and
air pressure tubing to the pressure switch
(Figure 105).
7. Using a 3/4" open end wrench or a crescent
wrench remove the manifold tube from the gas
control valve/thermostat (turning counterclockwise
-natural gas). Grasp the manifold tube and push
down slightly to free the manifold tube from the
gas control valve/thermostat (Figure 104).
8. Use a 1/4" nut driver or 1/4" socket & ratchet to
loosen the 2 hex head screws on the inner door
so the inner door/manifold/burner assembly can
be removed (Figure 106).
9. Remove inner door/manifold/burner assembly by
grasping the manifold and pulling straight back.
Care should be taken when inner door and burner
assembly passes through jacket opening that it
does not damage any of the electrical wiring or
the air pressure hose (Figure 107).
BURNER ORIFICE REMOVAL / REPLACEMENT
Figure 102.
HOTTER
Figure 103.
Figure 104.
IMPORTANT:
WHEN BRUSHING ON AN
APPROVED NONCORROSIVE
LEAK DETECTION SOLUTION,
DO NOT SPLASH SOLUTION
ONTO ELECTRICAL CON-
NECTIONS.
MANIFOLD TUBE
POWER SUPPLY
TRANSFORMER
CONNECTOR
Figure 105.
PRESSURE
SWITCH
47
g
COOLER
Electronic Control Display
ON
OFF
ON/OFF
SWITCH
UNPLUGGED
GAS CONTROL
VALVE/THERMOSTAT
PRESSURE
SWITCH/FAN,
FV SENSOR
CONNECTOR
IGNITER/
FLAME
SENSE
DISPLAY, ANODE
CONNECTOR
ROD CONNECTOR
MANIFOLD
TUBE