Adjustment Procedures
5-12
750-96 (revised 2010)
Model CB Packaged Boiler Manual
The pressures listed are based on 1000 BTU/cu. ft. natural gas at elevations up to 700 feet above sea level. For
installation at higher altitudes, multiply the selected pressure by the proper factor from Table 2.
5.7.2 — Gas Flow
The volume of gas flow is measured in terms of cubic feet and is determined by a meter reading. The gas flow
rate required for maximum boiler output depends on the heating value (BTU/cu. ft.) of the gas supplied. The sup-
plying utility can provide this information.
To obtain the required number of cubic feet per hour of gas, divide the heating value (BTU/cu. ft.) into the required
burner input (BTU/hr.). See Table 3 for input requirements.
5.7.3 — Pressure Correction
The flow rate outlined in the previous section is figured on a “base” pressure which is usually atmospheric or 14.7
psi.
Meters generally measure gas in cubic feet at “line” or supply pressure. The pressure at which each cubic foot is
measured and the correction factor for this pressure must be known in order to convert the quantity indicated by
the meter into the quantity which would be measured at “base” pressure.
TABLE 2. Higher Altitude Installation Factors
Altitude: Feet Above
Sea Level Correction Factor
1000 1.04
2000 1.13
2500 1.18
3000 1.22
4000 1.33
5000 1.44
6000 1.57
7000 1.70
8000 1.84
9000 2.01
TABLE 3. Input Requirements
Boiler Horsepower
Maximum Input:
BTU/hr.
50 2,092,000
60 2,511,000
70 2,929,000
80 3,347,000
100 4,184,000
125A 5,230,000
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