T-D2-IN / T-D2-OS Service Manual
Ver. 1.00
35
CONFIDENTIAL
10-19. Surge box
Unit Part #
#703
Takagi Part #
EK428
Checkpoint
A2,A3
Function
Protects the unit from high voltage and/or high electric current caused by
lightning.
There are 2 types of surge absorbers in the water heater. Surge absorber A is
activated by voltage higher than 220V, the other one is activated by voltage
higher than 680V.
Failure events
1. Open-failure of the absorber and/or fuse.
2. Short-failure of the absorber.
Effects on the water
heater if the fuse box
fails
1. Unable to protect the computer board if high voltage gets applied to the
unit. The computer board can short out, stopping all operations.
2. The unit cannot operate because the absorber shorted out, causing the
fuse to break open.
Error codes when the
surge box fails
N/A
Diagnostic
1.Visual
inspection:
burn
marks
on
components
and/or
connection/breakage of wires.
2. Check resistance and voltage: proper range of values shown below.
Color/Number of wires
White-Black
108 to 132 VAC
2 - 3 / 4 " ( 7 0 m m )
1
/
2
"
(
1
3
.
6
m
m
)
3
1
/
3
2
"
(
2
5
m
m
)
1
-
3
/
4
"
(
4
3
.
2
m
m
)
Surge absorber A: 220 V
Surge absorber B: 680 V
Fuse: 5A
