Gas Valve/Manifold Plate: Removal And Installation; Removal - A.O. Smith ATI-140H-N Service Handbook

14. Slowly open the gas valve and
check for leaks. If any gas leaks
appear, shut off the gas and turn
off power to the heater.
15. Turn on water to the heater and
test for proper opera on.
16. Verify that there are no water or
gas leaks.
17. Outdoor models:
Reinstall the front cover.
Indoor Models:
Insert the temperature controller
into the opening of the front cover,
then reinstall the front cover.
If there are any questions, please
contact technical support.
Manifold Screws:
• DO NOT remove the screws
shown below (indicated by
white, crossed-out circles).
• Remove the remaining
screws along the outside
edge (except as indicated).
Figure 77.
Gas Valve/
Manifold Plate:
Removal and
Installa on
Tools:
●
#2 Phillips Screw Driver
●
Gas Manometer

Removal

1. Shut off power by disconnec ng
the power cord or shu ng off the
power disconnect.
2. Shut off the gas supply to the
water heater.
3. Drain the water from the heater.
3.1 Close the shutoff valves on
the hot and cold sides of the
water heater.
3.2 If isola on valves are
installed, open the drain
ports.
3.3 If isola on valves are not
installed, remove the fi lter
(item 405, page 70) and
open the pressure relief
valve.
4. FOR INDOOR MODELS: Remove
the Temperature Controller (item
721, page 67) by disconnec ng
the white connectors that go to
the computer board.
5. Remove the computer board as
follows. (See Figure 24, page
35.)
Condensing Models: On-Demand Water Heater Service Handbook • 61
5.1 Disconnect all of the wires
from the computer board.
5.2 Remove the screw at the top,
then remove the board.
6. Remove the fuse box assembly
(items 703 & 120, 703,120, page
68):
6.1 Disconnect the connector at
the top port which comes
from the main power supply.
6.2 Disconnect the freeze
protec on heater wires
(yellow) by unlatching each
connector.
Inside models have 6 sets of
white connectors with yellow
wires. (Outside models
have 5 sets.) Two sets are
located above the assembly,
three are located below the
assembly, and one is located
below the secondary heat
exchanger on the right side.
(The last one is not installed
on outside models.)
7. Remove the igniter assembly from
the right-hand side, then slide the
black igniter tube off of the igniter
rod. (See "Igniter Assembly" and
"Igniter Rod Wire Connec on" in
Figure 24, page 35.)
8. Remove the Gas Valve and
Manifold Plate Assembly:
8.1 Unplug wire connectors from
the air/fuel ra o rod (AFR),
igniter, and fl ame rod.
Remove the screws that
secure the manifold plate
(Figure 24, page 35).
IMPORTANT: Refer to Figure
77 before you begin.