GS110 DIRECT VENT BOILER INSTALLATION AND OPERATION INSTRUCTIONS | Page 25 |
Figure 20- Air and Manifold Pressure
BOILER CHECKING & ADJUSTMENT
INPUT RATE
Gas appliances are rated based on sea level operation with no adjustment required at elevations up to 2000 feet. At elevations above 2000 feet, input ratings should be reduced by 4% for each 1000 feet 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 = 36 s/ft3
Input Rate = (1000 Btu/ft3)(3600 s/hr) 36 s/ft3
Input Rate = 100,000 Btu/hr
If the computed rate deviates by more than 5% from the rated input value of the unit adjust the gas valve pressure accordingly. DO NOT adjust the manifold pressure by more than 5%. If a proper rate cannot be maintained without adjusting the manifold pressure beyond the 5% limit, the burner orifice must be replaced. If the input rate is too low go to the next larger size orifice. if the input rate is too high, go to the next smaller size orifice.
PROPANE GAS:
The input rate for LP units is factory set based on the orifice size. The manifold pressure must be set at 1.9" W.C. and the orifice supplied with the boiler used unless the unit is to be derated for altitude.
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
NATURAL GAS:
Optimum results are obtained when the boiler is operated at its full input rating, with 1.9" W.C. of manifold pressure. The manifold pressure should not be more that 5% off this value. The gas valve pressure regulator has been preset at the factory. If adjustment is necessary the following steps must be followed:
1.Connect each side of a manometer to the two pressure ports shown in Figure 20 to obtain the manifold pressure.
2.Connect a flue gas analyzer to the vent pipe.
3.Rotate the regulator adjustment screw clockwise to increase the manifold pressure, counterclockwise to decrease it. Never force the regulator adjustment screw or the gas valve will be damaged!
4.The CO2 reading should fall between 7% and 9% with a CO reading of less than 50 ppm air free.
5.Adjust the air damper using the screw on the front
of the filter box if the CO2 and CO readings are not within the range given in step 4.
6.Recheck the manifold pressure and adjust it if necessary.
7.Replace the regulator adjustment screw cap and pressure port caps once the boiler is properly set up.
PROPANE GAS:
A manifold pressure of 1.9" W.C. must be maintained for proper operation of the boiler. If the manifold pressure is off by more than 5% or if the CO2 and CO readings are not within the range specified in step 4 above, adjust it according to steps 1 through 7 above.
