A.O. Smith Water Heater 520 Direct Vent Indoor Service Manual page 42

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 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 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
9 Check the manifold pressure in the water heater.
Malfunction description
1
520 Indoor / 520 Outdoor Service Manual
Diagnosis
restaurant.
& SV ) during
3
Diagnosis
42
CONFIDENTIAL
Ver. 1.00
Checkpoint
Cancellation method
Checkpoint