A.O. Smith 400A - Manual (Page 36)

36
CHECKLIST AND SERVICE INFORMATION
IMPORTANT
The installer may be able to observe and correct certain problems
which might arise when the unit is put into operation or when it is
re-fired after a prolonged shutdown. HOWEVER, it is recommended
that only qualified servicemen, using appropriate test equipment, be
allowed to service the heater.
BE SURE TO TURN OFF THE ELECTRICITY WHENEVER
POSSIBLE OR APPROPRIATE WHILE CHECKING EQUIPMENT.
WARNING
FAILURE TO FOLLOW THESE INSTRUCTIONS CAN RESULT IN
SERIOUS PERSONAL INJURY OR DEATH.
CAUTION:
LABEL ALL WIRES PRIOR TO DISCONNECTION WHEN
SERVICING CONTROLS. WIRING ERRORS CAN CAUSE
IMPROPER AND DANGEROUS OPERATION.
VERIFY PROPER OPERATION AFTER SERVICING.
BURNER OPERATIONAL PROBLEMS
. Refer to TROUBLESHOOTING.
NOT ENOUGH OR NO HOT WATER
1. Be certain the electrical disconnect switch serving the water
heater is in the ON position.
2. Check the fuses.
• The electrical disconnect switch usually contains fuses.
3. The capacity of the heater may have been exceeded by a large
demand for hot water.
• Large demands require a recovery period to restore water
temperature.
4. Colder incoming water temperature will lengthen the time
required to heat water to the desired temperature.
• If the heater was installed when incoming water
temperature was warm, colder water creates the effect
of less hot water.
5. Look for hot water wastage and leaking or open hot water
faucets.
6. Sediment or lime scale may be affecting water heater operation.
Refer to MAINTENANCE for details.
7. The heater’s temperature high limit sensor has activated. Press
the reset button on the thermostat.
8. Burner may not be firing at proper rate.
• Check gas pressure. Adjust to obtain required manifold
pressure.
9. Burner fan wheel may be dirty.
• Clean fan wheel with a stiff brush.
10. Condensate hose may be blocked where it connects to the
exhaust elbow.
• Verify the condensate drains from the unit without restriction.
WATER IS TOO HOT
1. Refer to WATER TEMPERATURE CONTROL.
WATER HEATER MAKES SOUNDS
1. Sediment or lime scale accumulations cause rumbling and
pounding noises when the heater is operating.
• The sounds are normal, however, the tank bottom should be
cleaned. Refer to MAINTENANCE for details.
2. Some of the electrical components of the water heater make
sounds which are normal.
• Contacts click or snap as the heater starts and stops.
• Transformers often hum.
WATER LEAKAGE IS SUSPECTED
1. Check to see if the water heater drain valve is tightly closed.
Also check the cleanout opening for leakage.
2. The apparent leakage may be condensation which forms on cool
surfaces of the heater and piping.
3. If the outlet of the relief valve is leaking it may represent:
• Excessive water pressure.
• Excessive water temperature.
• Faulty relief valve.
Excessive water pressure is the most common cause of relief valve
leakage. It is often caused by a “closed system”. If a check valve is
in the inlet system it will not permit the expanded hot water volume
to equalize pressure with the main. The relief valve must release this
water or the water heater or plumbing system will be damaged. Refer
to MAINTENANCE-RELIEF VALVE section in this manual.
When such a condition is encountered, local codes or inspection
agency should be consulted to determine which system is acceptable
in your area. See CLOSED SYSTEM section in this manual.
TROUBLESHOOTING
1. Verify that the allowable vent length has not been exceeded and
that the blower inlet screen has been removed if direct venting.
2. Verify the gas supply volume and pressure per table 3 and 4.
3. Verify that the condensation, which WILL be present in the heater
and exhaust vent, will drain.
4. Check supply wire polarity - hot to hot and neutral to neutral and
no "stray" current in neutral.
5. Heater is properly grounded.