A.O. Smith BTH 120-250(A) warranty Prior to Start UP, Operating Instructions, Adjustment Procedure

Models: BTH 120-250(A)

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PRIOR TO START UP

REQUIRED ABILITY

INSTALLATION OR SERVICE OF THIS WATER HEATER REQUIRESABILITY 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" (0-2.5Kpa) and 0-35" (0- 8.7Kpa) W.C. 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 (see Figure 15).

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.

NEVEROPERATETHEHEATERWITHOUTFIRSTBEINGCERTAINITISFILLED WITH WATERAND A TEMPERATUREAND A PRESSURE RELIEF VALVE IS INSTALLED IN THE RELIEF VALVEOPENING OF THE HEATER. DO NOT ATTEMPTTO 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.

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 ON PAGE 20 IN THIS MANUAL.

ADJUSTMENT PROCEDURE

INITIAL START-UP

A minimum gas supply pressure of 5.0" (1.25 kPa) W.C. (4.5" or 1.12 kPa)

on BTH 150 and 199) for natural gas (11.0" or 2.74 kPa W.C. for L.P. 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.

2.Check manifold pressure (see Table 4, page 20) using a pressure

gauge (manometer) connected to the manifold pressure tap on the

gas control valve, (Figure15).

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" (1 kPa)

on BTH 120 and 250 (3.5" or .87 kPa on BTH 150 and 199) for natural gas

(10.0" or 2.5 kPa W.C. for L.P. Gas) Water Column.

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 2000 feet

(610 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, page 20 for correct pressure.

b.Use this formula to “clock” the meter. Be sure other gas consuming appliances are not operating during this interval.

3600 X H = Btuh

T

Should it be necessary to adjust the gas pressure to the burner, to obtain the full input rate, the steps below should be followed:

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-199 heater)

T = 18.9 seconds

3600

X 1050 = 199,900 Btuh (59 Kw)

H = 1050 Btu/ft.3

18.9

BTUH = ?

For high altitude installations, compare result to the derated input required

for the elevation at the installation location.

c.Remove the pressure regulator cover screw (Figure 16) and adjust the pressure by turning the adjusting screw with a small screwdriver. Do not exceed 4.0" (1 kPa) on BTH 120 and 250 (3.5" (.87 kPa) on BTH 150 and 199) Water Column.

Clockwise to increase gas pressure and input rate.

Counterclockwise to decrease gas pressure and input rate.

d.“Clock” the meter as in step (b) above.

e.Repeat steps (c) and (d) until the specified input rate is achieved.

f. Turn the manual gas valve to “OFF”. Replace the pressure regulator cover screw. Remove the pressure gauge or manometer from the

manifold pressure tap. Replace the set screw in the manifold pressure

tap. If the gas pressure regulator cannot be adjusted to give the full

input rating with sufficient gas pressure at the valve, check to ensure

the unit is equipped with the correct orifice.

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A.O. Smith BTH 120-250(A) Prior to Start UP, Operating Instructions, Adjustment Procedure, Initial START-UP, Filling