T-D2-IN / T-D2-OS Service Manual
Ver. 1.00
23
CONFIDENTIAL
10-7. Heat exchanger
Unit Part #
#401
Takagi Part #
TU002 (IN)
EK437 (OS)
Checkpoint
N/A
Function
Absorbs heat from combustion and transfer it to water through the heat
exchanger pipes.
Failure events
1. Clogged heat exchanger fins and/or cracks on the heat exchanger walls.
2. Leaking exhaust gas.
3. Improper heat transfer can cause the water in heat exchanger to boil.
Effects on the water
heater if the heat
exchanger fails
1. Water leakage from the heat exchanger.
2. Exhaust gas leakage (if this occurs, an overheat cutoff fuse is in place to
detect this event and immediately stop the water heater from operating)
3. Abnormal sounds during combustion .
Error codes when the
heat exchanger fails
N/A
Diagnostic
1. Visual inspection: soot deposits, cracks on the heat exchanger walls, and/or
water leakage from the heat exchanger.
2. In the event of abnormal sounds during combustion:
A. Inspect for soot buildup inside the heat exchanger.
B. Inspect for scale buildup inside the heat exchanger pipes. Scale
buildup obstructs proper heat transfer to the water, thereby overheating the
heat exchanger and causing damage.
Color/Number of wires
N/A
T-D2-IN
T-D2-OS
1 0 - 5 / 8" ( 27 1 m m )
1
4
-
3
/
4
"
(
3
7
6
m
m
)
2
1
-
1
/
8
"
(
5
3
8
m
m
)
P r o
The heat exchanger of the T-D2-IN and T-D2-OS has the “Pro” mark as shown below.
1 0 - 5 / 8 " ( 2 7 1 m m )
P ro
1
2
-
1
/
4
"
(
3
1
3
m
m
)
1
8
-
3
/
4
"
(
4
7
5
m
m
)
