A.O. Smith 400A - Manual (Page 25)

5
DO NOT USE THIS HEATER IF ANY PART HAS BEEN UNDER
WATER. IMMEDIATELY CALL A QUALIFIED SERVICE TECHNICIAN
TO INSPECT THE HEATER AND TO REPLACE ANY PART OF THE
CONTROL SYSTEM AND ANY GAS CONTROL WHICH HAS BEEN
UNDER WATER.
LIGHT THE UNIT IN ACCORDANCE WITH THE OPERATING
INSTRUCTIONS LABEL ATTACHED TO THE HEATER.
THESE INSTRUCTIONS ARE REPEATED IN THE LIGHTING AND
OPERATING LABEL ILLUSTRATION IN THIS MANUAL.
ADJUSTMENT PROCEDURE - INITIAL START-UP
A minimum dynamic gas supply pressure of 5.2" W.C. (1.29 kPa)
for Natural Gas and 11" W.C. (2.74 kPa) for LP Gas is required
before making any adjustment to the gas control pressure regulator
Attempts to adjust the regulator during periods of low gas supply
pressure could result in overfiring of the heater when the gas supply
pressure returns to normal.
1. Check gas line pressure with a manometer, adjust the gas supply
line pressure per table 4.
2. Check manifold pressure (see Table 4) using a pressure gauge
(manometer) connected to the manifold pressure tap on the gas
control valve, (Figure 15).
If full rate adjustment is required, remove cover screw from top of
the gas control valve, (Figure 15).
Using a small screwdriver, turn adjusting screw clockwise to
increase or counterclockwise to decrease gas pressure to
obtain 4.0" W.C. (0.996 kPa) for Natural Gas and 10" W.C. (2.49
kPa) for LP gas.
3. Cycle the burner on and off several times to check its operation.
4. Check the operation of the limit and operating controls.
5. Check the vent system seams and joints and ensure that there
is no discharge of flue products into the room.
6. Check the input rate:
For appliance installation locations with elevations above 10,000
feet (3,048 m) refer to HIGH ALTITUDE INSTALLATIONS section
of this manual.
a. Attach a pressure gauge (manometer) to the manifold pressure
tap (Figure 16) and refer to Table 4 for correct pressure.
b. Use this formula to “clock” the meter. Be sure other gas
consuming appliances are not operating during this interval.
3600
T
T = Time in seconds to burn 1 cubic foot of gas. (With a stopwatch
read the gas meter and measure the amount of time required for
the heater to consume 1 cubic foot of gas.)
H = Heating value of gas (in Btu’s per cubic foot of gas).
Btuh = Actual heater input rate, in Btuh.
EXAMPLE: (Using BTH-300 heater)
T = 12.6 seconds
H = 050 Btu/ft. 3
BTUH = ?
For high altitude installations, compare result to the derated input
required for the elevation at the installation location.
Should it be necessary to adjust the gas pressure to the burner,
to obtain the full input rate, the steps below should be followed:
PRIOR TO START UP - REQUIRED ABILITY
INSTALLATION OR SERVICE OF THIS WATER HEATER REQUIRES
ABILITY EQUIVALENT TO THAT OF A LICENSED TRADESMAN IN
THE FIELD INVOLVED. PLUMBING, AIR SUPPLY, VENTING, GAS
SUPPLY AND ELECTRICAL WORK ARE REQUIRED.
Before attempting start-up, thoroughly study and familiarize yourself
with the exact sequence of operation and all other details on the
specific heater being used.
The power burner is equipped with an ignition system which
automatically sequences prepurge and ignition, senses and
ignites main burner flame and sequences burner operation.
Heater is equipped with an ignition control which locks out after
three unsuccessful ignition attempts. Familiarize yourself with the
sequence of operation of this unit prior to start-up.
Be certain that the water heater is full of water, that air is purged
from all lines, there are no leaks (gas and water), and all inlet water
lines are open.
The following test equipment should be on hand (all test
equipment must be acclimated to ambient temperature before
calibration and use.)
– Two U-tube manometers or calibration 0-10" W.C. (0-2.5Kpa) and
0-35" W.C. (0-8.7Kpa) pressure gauges.
• Attach a gas pressure gauge or manometer to the upstream side
of main gas cock and a gas pressure gauge or manometer to the
manifold pressure tap.
• You are now ready to begin the burner start-up procedure.
OPERATING INSTRUCTIONS
IMPORTANT
IT IS RECOMMENDED THAT A QUALIFIED SERVICE TECHNICIAN
PERFORM THE INITIAL FIRING OF THE HEATER. AT THIS TIME THE
USER SHOULD ASK THE TECHNICIAN ANY QUESTIONS IN REGARD
TO THE OPERATION AND MAINTENANCE OF THE UNIT.
CAUTION
BEFORE PROCEEDING WITH THE OPERATION OF THE UNIT,
MAKE SURE HEATER AND SYSTEM ARE FILLED WITH WATER
AND ALL AIR IS EXPELLED FROM HEATER AND PIPING.
NEVER OPERATE THE HEATER WITHOUT FIRST BEING
CERTAIN IT IS FILLED WITH WATER AND A TEMPERATURE AND
A PRESSURE RELIEF VALVE IS INSTALLED IN THE RELIEF VALVE
OPENING OF THE HEATER. DO NOT ATTEMPT TO OPERATE
HEATER WITH COLD WATER INLET VALVE CLOSED.
FILLING:
1. Close the heater drain valve.
2. Open a nearby hot water faucet to permit the air in the system
to escape.
3. Fully open the cold water inlet pipe valve allowing the heater
and piping to be filled.
4. Close the hot water faucet as water starts to flow.
5. The heater is ready to be operated.
THE MAIN MANUAL GAS SHUTOFF VALVE MUST HAVE BEEN CLOSED
FOR AT LEAST FIVE (5) MINUTES. THIS WAITING PERIOD IS AN
IMPORTANT SAFETY STEP. ITS PURPOSE IS TO PERMIT GAS THAT
MIGHT HAVE ACCUMULATED IN THE COMBUSTION CHAMBER TO
CLEAR. IF YOU DETECT GAS AT THE END OF THIS PERIOD, DO NOT
PROCEED WITH LIGHTING. RECOGNIZE THAT GAS ODOR, EVEN IF
IT SEEMS WEAK, MAY INDICATE THE PRESENCE OF ACCUMULATED
GAS SOMEPLACE IN THE AREA WITH A RISK OF FIRE OR EXPLOSION.
SEE THE FRONT PAGE FOR STEPS TO BE TAKEN.
X H = Btuh
3600
X
1050 = 300,000 Btuh (87.9 kW)
12.6