520 Indoor / 520 Outdoor Service Manual
Ver. 1.00
26
CONFIDENTIAL
10-9. Secondary heat exchanger
Unit Part #
446
AOS Part #
319143-108
Checkpoint
N/A
Function
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%.
Failure event
1. Water leakage from the secondary heat exchanger.
2. Leaking exhaust gas.
Effects on the water
heater if the secondary
heat exchanger fails
1. Water leakage from the secondary heat exchanger.
2. Exhaust gas leakage
3. Abnormal sounds during combustion
Error
codes
when
secondary
heat
exchanger fails
N/A
Diagnostic
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.
Color/Number of wires
N/A
1 0 - 5/ 8 " ( 2 6 9 .4 m m )
2 - 3 / 4 " ( 7 0 .8 m m )
7
-
1
/
2
"
(
1
8
9
m
m
)
