Service manual

SC Series Boilers – Installation and Service Manual
21
3.7 CHECK INPUT & ORIFICES
For safety, the input shown on rating plate must not be exceeded. Check with the following table
that the orifice size and input rate shown on your boiler rating plate match your application, i.e. boiler
model, fuel type, and altitude. To adjust manifold pressure, follow the procedure described in Section
3.6. If the derated input rating for high altitude requires a change in orifice size, contact the boiler
manufacturer.
FOR CANADA
Natural Gas Propane
Model
0 to 2,000 feet 2,000 to 4,500 feet 0 to 2,000 feet 2,000 to 4,500 feet
All
φ7/64” orifice
standard input
#36 orifice
10% derate input by
adjusting manifold
pressure
#50 orifice
standard input
#51 orifice
10% derate input by
adjusting manifold
pressure
NOTE: For elevations above 4,500 feet reduce high altitude input 4% for each additional 1000 feet.
Reference Natural Gas and Propane Installation Code B149.1, 3.22 High Altitude Installations
Example of High Altitude Derate
Boiler: SC-140
Altitude: 5,500 feet
Standard Input (0-2,000 ft) = 140,000 Btu/h
High Altitude Input (2000 to 4,500 ft) = 140,000 x 0.90 = 126,000 Btu/h
% Reduction for additional 1000 ft = 4% x 1 = 4%
Input at 5,500 ft = Derate High Altitude Input by 4%
= 126,000 Btu/h x (1 - 0.04)
= 126,000 Btu/h x 0.96
= 120,960 Btu/h
FOR UNITED STATES
Natural Gas Propane
Model
0 to 2,000 feet Over 2,000 feet 0 to 2,000 feet Over 2,000 feet
All
φ7/64” orifice
standard input
Input must be reduced
4% for each 1000 feet
above sea level. *
#50 orifice
standard input
Input must be reduced
4% for each 1000 feet
above sea level. *
*Reference National Fuel Gas Code ANSI Z223.1, 8.1.2 High Altitude.
Example of High Altitude Derate
Boiler: SC-105
Altitude: 5,000 feet
Standard Input (0 to 2,000 ft) = 105,000 Btu/h (from page 2)
% Reduction for 5,000 ft = 4% x 5 = 20%
Input at 5,000 ft = Derate Standard Input by 20%
= 105,000 Btu/h x (1 - 0.20)
= 105,000 Btu/h x 0.80
= 84,000 Btu/h