A.O. Smith GTS-305-NE Service Manual page 39

Component Replacement Instructions
Heat Exchanger
Disconnect PC Board (Figure 39)
11. Remove 1 screw connecting the PC
Board to the heat exchanger
assembly.
Remove Gas Manifold (Figure 39)
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.
Remove Burner and Burner Cover Plate (Figure 40)
14. Pull out the ignition line and remove the gas manifold.
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.
8 screws
(burner cover plate)
2 screws (burner)
Disconnect Wire Harness Attachments and Screws Holding the Heat Exchanger
17. Unscrew the ignition line connection. (Figure 40)
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 41)
3 screws
On-Demand Gas Tankless Water Heater Service Manual
505e/o
Figure 41
39
Figure 39
Ignition line
6 screws (gas manifold)
PC Board screw
3 machine screws
(gas valve)
Figure 40
Ignition line
connection
2 screws
Figure 42