Replacing The Heat Exchanger (Outdoor Models); Removing Heat Exchanger Components (Outdoor Models) - A.O. Smith ATI-140H-N Service Handbook

Replacing the
Heat Exchanger
(Outdoor Models)
Tools:
#2 Phillips Screw Driver
(a magnetic tip is helpful)
WARNING!
□
Disconnect power by opening
the circuit breaker or removing
the fuses before installing or
servicing.
□
Use a non-contact circuit tester
to confirm that power is off
before working on or near any
electrical parts.
□
Ensure that the gas supply is
shut off at the manual gas
shutoff valve.
□
Replace the front cover after
servicing.
Consider removing the following
sections from this manual for easy
reference:
•
"Component Diagrams/Item
Numbers" (starting on page
67).
•
Figure 25, page 36, which
shows the location of basic
components.
This will allow you to lay the loose
pages beside this manual for easier
reference.
Also, screw sizes vary. We
recommend bagging and labeling
screws as you remove them, or
reinstall them in their proper places as
you proceed with disassembly. This
will make reassembly easier.
46 • Condensing Models: On-Demand Water Heater Service Handbook
Removing Heat
Exchanger Components
(Outdoor Models)
1. Shut the unit down as follows:
1.1 Shut Off power and gas
supply as follows:
1.1.1 Shut off Power by
disconnec ng the power
cord or shu ng off the
power disconnect.
1.1.2 Shut off the gas supply to
the water heater at the
manual gas shutoff valve.
1.2 Drain the water from the
heater as follows:
1.2.1 Close the shutoff valves on
the hot and cold side of the
heater.
1.2.2 IF isola on valves are
installed: open up the drain
ports.
1.2.3 IF isola on valves are not
installed: remove the fi lter
(item 405, page 70) and
open the pressure relief
valve.
2. Remove the computer board as
follows (item 701, page 68; see
also Figure 25 on page 36):
CAUTION:
•
During the next steps, consider
taking a digital photo to aid in
reassembly.
•
Do not touch the circuit board
components. Doing so may
cause damage by electrostatic
discharge.
2.1 Disconnect all wire
connectors from the
computer board.
2.2 Remove the screw at the
top of the computer board
assembly, then remove the
board (Figure, p. 36).
3. Remove the fuse box assembly
(items 703, 120; page 46):
3.1 Disconnect the connector at
the top port which comes
from the main power supply.
3.2 Disconnect the freeze
protec on heater wires.
There are 5 sets of white
connectors with yellow
wires (two above the
assembly and three below
the assembly).
3.3 Remove the screw that
secures the fuse box and li
the fuse box away.
4. Remove the fl ow sensor/control
valve (item 402, page 70; see
also Figure 25, page 36):
4.1 Remove fasteners 16A and
14-22 (items 458 and 459,
page 70).
4.2 Pull the cold connec on
tube (item 462, p. 70)
from the outlet of the fl ow
sensor/control valve and
li the valve off of the inlet
connec on. You may have
to twist the valve off of the
inlet connec on.
5. Remove the cold connec on tube
(item 462, page 70) as follows:
5.1 Disconnect fastener 14-22
(item 458, page 70).