T-D2-IN / T-D2-OS Service Manual
Ver. 1.00
37
Natural of Fault Diagnosis
Checkpoint
・The hot water is not
available when a fixture
is opened
5 Check that the filter on the cold water inlet is clean.
6 Check whether or not the unit is frozen.
7 Check if there is enough gas in the tank. (for propane units)
・The hot water turns cold
and stays cold
1 Check whether the flow rate is high enough to keep the water
heater running.
2 Check if there is a recirculation system installed and check also if
the recirculation line has enough check valves.
3 Check that the filter on the cold water inlet is clean.
4 Check that the fixtures are free from debris and obstructions.
・The fan motor is still
spinning after operation
has stopped
1 This is normal operation. After operation has stopped, the fan
motor keeps its running 15 to 70 seconds in order to re-ignite
quickly, as well as purge all the exhaust gas out of the flue.
・Abnormal sound from
water heater
1 Check the gas type of the water heater.
2 Check how long the water heater has been installed and in use.
3 Check the installation place.
4 Check the altitude/elevation of area of where the water heater
installed.
5 Check the vent length, when the water heater has been installed
indoors.
6 Check if there is any blockage in the intake air and/or exhaust.
7 Check if there is dust and lint in burner and heat exchanger, when
the water heater has been installed in laundry room.
8 Check if there is grease and dirt in burner and fan motor, when
the water heater has been installed in restaurant.
Check the manifold pressure in the
Natural of
Fault
Malfunction description Cancellation method
・ Fluctuation
of hot water
temperature
-Fault of gas solenoid valves (SV
1
& SV
3
) during
change of the combustion stage
Fault of flow adjustment valve
1 Check whether the filter in cold water inlet is cleaned.
2 Check whether the gas supply pressure is adequate.
Check for cross connections between cold water lines and hot water lines.
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