Secondary Heat Exchanger - A.O. Smith T-H2-DV Service Manual

10-9. Secondary heat exchanger

Unit Part #
Function
Failure event
Effects on the water
heater if the secondary
heat exchanger fails
Error codes when
secondary heat
exchanger fails
Diagnostic
Color/Number of wires
446 Takagi Part #
Absorb latent heat from exhaust gas and transfer the water through the
secondary heat exchanger pipes, which can improve heat efficiency of the
unit by approximately 10%.
1. Water leakage from the secondary heat exchanger.
2. Leaking exhaust gas.
1. Water leakage from the secondary heat exchanger.
2. Exhaust gas leakage
3. Abnormal sounds during combustion
1. Visual inspection: soot deposits, cracks on the secondary heat exchanger
walls, and/or water leakage from the secondary heat exchanger.
2. In the event of abnormal sounds during combustion:
Inspect for soot buildup inside the secondary heat exchanger.
T-H2-DV/T-H2-OS Service Manual
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CONFIDENTIAL
Ver. 1.01
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