Non-Condensing Models - AO Smith Water Heaters

Troubleshooting GuideREPLACING THE HEAT EXCHANGERThere are many possible causes of a heat exchanger failure:• Contaminated air with a high level of dust, lint, sand, grease, aerosols or other contaminants,can become airborne and enter the air intake. The contaminants build up within the fan andburner assembly causing abnormal flame conditions due to lack of combustion air, damagingmany components of the unit.• Scale can build up from very hard water. Lime scale will form on the inside of the heatexchanger tubes readily at high temperatures. This scale prohibits heat from reaching the waterwhich causes excessive heat within the heat exchanger copper, and it will eventually burn andleak.Along with changing the heat exchanger, it is important to identify the CAUSE of the need forreplacement, and fix the problem so it does not occur again1) TOOLS ‐ Gather the following materials together:a. Degreaser in a pump action bottleb. Sheet of 100 Grit Sandpaperc. #2 Philips Screw Driverd. Needle‐Nosed Plierse. Duct Tapef. Flashlightg. Air Compressorh. Old Towels, at Least Three2) PREPARE THE UNITa. POWER ‐ Disconnect power to your unit.b. GAS ‐ Shut off the gas supply to the unit.c. WATER – Drain the unit. Refer to p. 21 for instructions.3) REMOVE MANIFOLD/GAS ASSEMBLY, BURNERa. Follow steps 1‐7 of the previous section, “Cleaning the Combustion Components”. This will tellyou how to remove the PCB, manifold/gas assembly, and burner4) WIRES ‐ There are several wire clips that need to be removed to free the heat exchangera. Locate the brown wire clip connected to the GFI, and disconnect it.b. On the bottom left, disconnect the ceramic heating elements (white wires).c. Locate the white bypass valve clip on the left‐hand side of the combustion chamber withred/black wires. Disconnect it.d. Upwards toward the left side, remove a blue connection to the over‐heat cutoff fusee. Remove the two spade connections on the high limit switch.f. Disconnect the igniter plug (purple wires and blue plug) at the bottom right.g. Along the bottom, disconnect the plug into the proportional valve (red & white wires).29| Page