Heat Exchanger 305E - A.O. Smith GTS-305-NE Service Manual

Component Replacement Instructions
Heat Exchanger
Disconnect PC Board (Figure 31)
11. Remove 1 screw connecting the PC
Board to the heat exchanger assembly.
Remove Gas Manifold (Figure 31)
12. Remove the 6 screws that attach the gas
manifold to the combustion chamber
(part of the heat exchanger assembly).
13. Remove the 3 screws that attach the gas
manifold to the gas valve. These screws
are machine screws and must be used at
these locations.
14. Pull out the ignition line and remove the
gas manifold.
Remove Burner and Burner Cover Plate (Figure 32)
15. Remove the 8 screws attaching the burner cover plate to the combustion chamber. Move the cover plate to
the side. It is not necessary to disconnect the wire harness from the burner cover plate.
16. Remove the 2 screws attaching the burner to the heat exchanger. Pull out the burner.
17. Unscrew the ignition line connection. (Figure 32)
8 screws
(burner cover plate)
2 screws (burner)
Disconnect Wire Harness Attachments and Screws Holding the Heat Exchanger
18. Remove the wire harness attachments - sensors, heating elements, fusible link brackets. Ensure that the
small O-ring in the thermistor is removed.
19. Remove 3 screws behind the fan. (Figure 33)
20. Remove 2 screws above the exhaust. Pull assembly from the unit. (Figure 34)
3 screws
On-Demand Gas Tankless Water Heater Service Manual
305e
Figure 31
Figure 33
36
Ignition line
6 screws (gas manifold)
PC Board screw
3 machine screws
(gas valve)
Figure 32
Ignition line
connection
Figure 34
2 screws