A.O. Smith 710 ASME Service Manual page 36

Natural of Fault
・The hot water is not
available when a fixture
is opened
・ The hot water turns cold
and stays cold
・The fan motor is still
spinning after operation
has stopped
・Abnormal sound from
water heater
Natural of
Fault
-Fault of gas solenoid valves (SV
・ Fluctuation
change of the combustion stage
of hot water
temperature
-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.
3
Check for cross connections between cold water lines and hot water lines.
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)
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.
1 This is normal operation. After operation has stopped, the fan
motor keeps its running for 35 seconds in order to re-ignite
quickly, as well as purge all the exhaust gas out of the flue.
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 the type of vent cap, when the water heater has been
installed outdoors.
7 Check if there is any blockage in the intake air and/or exhaust.
8 Check if there is dust and lint in burner and heat exchanger, when
the water heater has been installed in laundry room.
9 Check if there is grease and dirt in burner and fan motor, when
the water heater has been installed in
10 Check the manifold pressure in the water heater.
Malfunction description
1
710 / 710 ASME Service Manual
Diagnosis
restaurant.
& SV ) during
3
Diagnosis
36
CONFIDENTIAL
Ver. 1.00
Checkpoint
Cancellation method
Checkpoint