High Altitude; Natural Gas At High Altitudes - Rheem 801S Series Installation Instructions Manual

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 NATIONAL FUEL GAS CODE, ANSI Z223.1/NFPA 54.
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 DETER-
MINE IF AN ORIFICE CHANGE WILL BE NECESSARY
AND HOW TO DETERMINE THE NEW ORIFICE SIZE.
34" 80 Plus furnaces installed above 2,000 ft. require the furnace
to be de-rated 4% per thousand feet.
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 F:
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.

HIGH ALTITUDE

From Table F.1 of National Fuel Gas Code Handbook, 2002 (3.5
w.c. column).
Orifice required at Sea Level: #40
From Table F.4 of National Fuel Gas Code Handbook, 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 F.1 of Natural Fuel Gas Code Handbook, 2002 (3.5
w.c. column).
Orifice required at Sea Level: #43
From Table F.4 of National Fuel Gas Code Handbook, 2002
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
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