35
High Altitude
HIGH ALTITUDE
34” 80 Plus furnaces installed above 2,000 ft . require the furnace
to be de-rated 4% per thousand feet above sea level .
IMPORTANT:
Factory installed orifices are calculated and sized
based on a sea level Natural Gas heating value of 1050 BTU per
cubic ft.
NOTE: Orifices are available through your local distributor .
Reference Table 8 for approximate orifice sizing .
The following are examples of orifice sizing using the National
Fuel Gas Code Appendix E, 2015 edition .
For a simplified estimation of orifice size based on gas heating
value and elevation, Table 8 may be used . However, calculations
are the best method .
Example: 900 BTU/ft
3
Regional Natural Gas Heating Value
I/H = Q
25000 / 900 = 27 .78 ft
3
I = Sea Level input (per burner): 25000
H = Sea Level Heating Value: 900
Q = 27 .78 ft
3
Natural Gas per hour .
From Table E1 .1a of
National Fuel Gas Code, 2015
(3 .5
(
w .c .
column) .
Orifice required at Sea Level: #40
From Table E1 .1d of
National Fuel Gas Code, 2015.
Orifice re-
quired at 5000 ft . elevation (4% de-rate per thousand ft): #42
Orifice required at 8000 ft . elevation (4% de-rate per thousand
ft .): #44
Example: 1050 BTU/ft3 Regional Natural Gas Heating Value
I / H = Q
25000 / 1050 = 23 .81ft
3
I = Sea Level input (per burner): 25000
H = Sea Level Heating Value: 1050
Q = 23 .81 ft
3
Natural Gas per hour .
From Table E1 .1a of
National Fuel Gas Code, 2015
(3 .5
9
w .c .
column) .
Orifice required at Sea Level: #43
From Table E1 .1d of
National Fuel Gas Code, 2015
Orifice required at 5000 ft . elevation (4% de-rate per
thousand ft .): #45
Orifice required at 8000 ft elevation (4% de-rate per
thousand ft): #47
ORIFICE ORDERING INFORMATION
Orifice sizes are selected by adding the 2-digit drill size required
in the orifice part number . Drill sizes available are 39 through 64;
metric sizes available 1 .10mm (-90) and 1 .15mm (-91):
Orifice Part Number 62-22175-(drill size)
Example:
# 60 drill size orifice required
Part # 62-22175-60
NATURAL GAS AT HIGH ALTITUDES
!
WARNING
INSTALLATION OF THIS FURNACE AT ALTITUDES ABOVE
2000 FT (610 m) SHALL BE IN ACCORDANCE WITH LOCAL
CODES, OR IN THE ABSENCE OF LOCAL CODES, THE NA-
TIONAL FUEL GAS CODE, ANSI Z223 .1/NFPA 54 .
!
CAUTION
ELEVATIONS ABOVE 2000 FT . REQUIRE THAT THE FUR-
NACE INPUT RATING BE ADJUSTED AND THAT THE
SIZE OF THE BURNER ORIFICES BE RE-CALCULATED
BASED ON ELEVATION AND GAS HEATING VALUE . THE
BURNER ORIFICES MAY (OR MAY NOT) NEED TO BE
CHANGED . THE FOLLOWING EXAMPLES SHOW HOW
TO DETERMINE IF AN ORIFICE CHANGE WILL BE NEC-
ESSARY AND HOW TO DETERMINE THE NEW ORIFICE
SIZE .
Summary of Contents for 801C Series
Page 52: ...52 CM 0917...
