T-D2-IN / T-D2-OS Service Manual
Ver. 1.00
26
CONFIDENTIAL
10-10. Bypass valve
Unit Part #
#403
Takagi Part #
EKK0U
Checkpoint
J1
Function
1. Mixes hot water from the heat exchanger with cold water from the
water inlet in order to modulate and control the water heater’s outlet
water temperature.
2. Keeps the water temperature in the heat exchanger stable, preventing
low-temperature corrosion by reducing condensation buildup in heat
exchanger.
Failure events
1. Water leakage from valve.
2. The valve cannot modulate properly.
Effects on the water heater
if bypass valve fails
1. Water leakage from failed valve can damage other water heater
components.
2. Temperature fluctuations in the hot water output.
Error codes when bypass
valve fails
N/A
Diagnostic
1. Visual inspection: connection/breakage of wires.
2. Check voltages and resistance: proper range of values shown below.
Color/Number of wires
Red - Black
7 to 16 VDC and 0.09 to 0.2 k
Ω
The physical appearance of the bypass valve is similar to that of the flow adjustment valve.
However, their functions differ and cannot be substituted for each other.
B Y P A S S
W A T E R I N
B Y P A S S
W A T E R O U T
Bypass
valve
B Y P A S S
W A T E R I N
B Y P A S S
W A T E R O U T
>
P
P
E
-
G
F
<
1- 7 / 8 " ( 4 7 m m )
3
-
3
/
8
"
(
8
4
.
4
m
m
)
2 - 5 / 8 " ( 6 7 .5 m m )
