A.O. Smith Residential Power Vent Gas Water Heaters with Hot Surface Ignition Instruction Manual page 26

Operating (cont'd)
WARNING
BEFORE OPERATING [PROPANE (L.P.) GAS WATER
HEATERS]: Propane (L.P.) gas is heavier than air. Should
there be a leak in the system, the gas will settle near the
ground. Basements, crawl spaces, skirted areas under
manufactured (mobile) homes (even when ventilated),
closets and areas below ground level will serve as pock-
ets for the accumulation of this gas. Before attempting
to operate the water heater or turning a nearby electri-
cal light switch, be absolutely sure there is no accumu-
lated gas in the area. Search for odor of gas by sniffing
at ground level in the vicinity of the appliance. If odor
is detected, follow the steps indicated at "For Your
Safety" on the cover page of this manual, then leave the
premises.
Operating instructions are located on front of the water
heater, above or to one side of the gas control valve. See
page 27.
WARNING
AN ODORANT IS ADDED TO THE GAS USED BY
THIS WATER HEATER.
FOR YOUR SAFETY
IF YOU SMELL GAS:
1. Do not try to light any appliance.
2. Do not touch any electrical switch; do not use any
phone in your building.
3. Immediately call you gas supplier from a neighbor's
phone. Follow the gas supplier's instructions.
4. If you cannot reach your gas supplier, call the fire
department.
CHECK FOR LEAKS
Be sure to check all your gas pipes for leaks before operat-
ing your water heater. Use a soapy water solution, not a
match or open flame. Check the factory gas fittings when
the main burner is turned "ON".
WATER HEATING IGNITION SEQUENCE
(Make sure gas and electric power are connected properly)
1. The ignition control module is powered and monitors the
system, waiting for a call for heat from the thermostat.
2. The thermostat calls for heat by reading a resistance
value within a given range directly proportional to water
temperature.
3. The control module:
a) Checks the pressure switch for an open circuit.
b) Energizes the blower.
c) Checks the pressure switch for a closed circuit to
prove draft.
d) Sends line voltage to the hot surface igniter with a
20-second warm up period.
e) Opens the gas valve and checks the sensing rod for
flame.
4. The burner heats the water to the desired thermostat
setting.
a) The resistance in the thermostat rises to the value
selected by the temperature control knob.
b) The control module closes the gas valve and 5
seconds later, removes power from the blower.
5. Cycle is completed.
CONTROL SEQUENCE - HOT SURFACE DIRECT IGNITION
Pre-purge
HSI Warm-up
Ignition Activation Period
Flame Recognition Period
Ignition Trial
Interpurge
Post-purge
Retries
Reset from Lockout
Flame Sensing (Nominal)
HSI Off/Run Mode
26
5 sec.
20 sec.
4 sec.
1sec.
4 sec.
5 sec.
5 sec.
2
1 hr.
4.0 µ DC