41 Page
240 (T-H3J), 340 (T-H3S) and 540 (T-H3) models Service Manial
Ver. 1.00
CONFIDENTIAL
10-16. Overheat cut off fuse
Part# • 319143-149 (EK333) Unit Part# #413
Function
-The overheat cutoff fuse contains solder with a melting point of 430 ˚F
(221 ˚C).
-Detects excessive temperatures within the water heater, especially
around the heat exchanger and combustion chamber. Upon detection,
communication between the computer board and gas valves will sever,
shutting down the water heater instantly. The "111" or "121" error code
will display.
Failure events
1. Unable to detect the excessively high temperatures within the water
heater.
Effects on the water heater
if the overheat cutoff fuse
fails
1. Flames from burner may penetrate a ruptured/damaged heat exchanger.
2. Gas valves will not operate.
Error codes when the
overheat cutoff fuse fails
111 121
Diagnostic
1. Visual inspection: connection/breakage of wires.
2. Check voltages and resistance: proper range of values shown below.
Color / Number of wires Blue-Blue Less than 1.0 Ω Checkpoint C2
5-1/32" (128 mm)
Solder will melt at temperature exceeding 430 ˚F (± 9 ˚F) or 221 ˚C (± 5 ˚C)
The O.H.C.F. has a red line on itself.
To Next Page
Loading...
Need help?
General
