Smith Cast Iron Boilers GT Series Boiler Checking & Adjustment, Input Rate, Main Burner Flame

GT INSTALLATION AND OPERATION INSTRUCTIONS Page 33

BOILER CHECKING & ADJUSTMENT

Input Rate

Gas appliances are rated based on sea level operation with no adjustment required at elevations up to 2000 ft, 610 m. At elevations above 2000 ft, 610 m, input ratings should be reduced by 4% for each 1000 ft, 305 m, above sea level. Check the input rate as follows:

NATURAL GAS:

1.Turn off all other gas appliances that use the same gas meter as the boiler.

2.Call the gas company for the gas heating value.

3.Start the boiler and let it run for 15 minutes.

4.Using the gas meter and a stopwatch, clock the time that it takes to burn 10 cubic feet of gas and divide the time by 10.

5.Insert the heating value and the time, in seconds, into the formula below.

Input Rate = Heating Value(Btu/ft3)(3600 s/hr) Flow Rate(s/ft3)

EXAMPLE: If the heating value = 1000 Btu/ft3 and the flow rate = 18 s/ft3

Input Rate = (1000 Btu/ft3)(3600 s/hr) 18 s/ft3

Input Rate = 200,000 Btu/hr

If the computed rate deviates by more than 5% from the rated input value of the unit adjust the gas valve pressure according to the GAS PRESSURE ADJUSTMENT instructions that follow.

PROPANE GAS:

The input rate for LP units is factory set based on the orifi ce size. Use the factory supplied kit to convert the boiler to LP. A combusiton analyzer must be used to ensure that the CO2 reading falls between 9% and 10.5% with a CO reading of less than 175 ppm air free.

CAUTION: Never increase the input to the boiler above that for which it is rated. Doing so can cause premature failure of the boiler!

Gas Pressure Adjustment

Optimum results are obtained when the boiler is operated at its full input rating. If adjustment is necessary the following steps must be followed:

1.Connect a flue gas analyzer to the vent pipe.

2.Rotate the input adjustment screw clockwise to decrease the manifold pressure, counterclockwise to increase it, Figure 41 or 42. The input screw on the GT-150 & 200 is a multi turn needle valve. From fully open to fully closed is approximately 17 turns. A typical adjustment is 0 to 1 turn for natural gas, 0 to 3 turns for LP. The input screw on the GT-400 turns a geared ball valve with a 4 to 1 ratio.Two turns will take the valve from fully open to fully closed. 0 to 1/4 turn is a typical adjustment. Never force the input adjustment screw or the gas valve will be damaged!

3.For natural gas the CO2 reading should fall between 8% and 9.5% with a CO reading of less than 175 ppm air free. For LP gas the CO2 reading should fall between 9% and 10.5% with a CO reading of less than 175 ppm air free.

Main Burner Flame

A properly adjusted main burner fl ame will produce a tight blue fl ame pattern about 1/2 in, 13 mm, tall from the burner’s surface, Figure 44. A yellow fl oating or tall stringy flame is not normal and must be corrected.

WARNING:Yellow, floating flames indicate a lack of combustion air. DO NOT operate the boiler until the problem is solved or severe personal injury or death may occur!

Figure 44 - Burner Flame

Thermostat Adjustment

Set the heat anticipator to 1.1 amps when controlling the boiler directly. For zoned systems set the heat anticipator to match the amp draw of the zone valves or pump relays.