50
Example: 1050 BTU/ft
3
Regional
Natural Gas Heating Value
I / H = Q
15000 / 1050 = 14.63 ft.
3
I = Sea Level input (per burner): 15000
H = Sea Level Heating Value: 1050
Q = 14.28 ft.
3
Natural Gas per hour.
From Table F.1 of National Fuel Gas
Code Handbook, 2002 (3.5” w.c. column)
Orifice required at Sea Level: #50
From Table F.4 of National Fuel Gas
Code Handbook, 2002
Orifice required at 5000 ft. elevation (4%
de-rate per thousand ft.): #51
Orifice required at 8000 ft. elevation (4%
de-rate per thousand ft.): #52
LP GAS AT HIGH ALTITUDE
ELEVATIONS
LP Gas is a manufactured gas that has
consistent heating value across most
regions.
The NFGC guidelines are used with the
following exception:
The recommended LP Gas high altitude
orifice selections differ slightly in that the
NFGC LP orifice chart, as they are not
accurate for Rheem products. The
National Fuel Gas Code LP orifices are
based on an 11" of water column
pressure at the orifice, which differs from
Rheem products that use 10" of water
column at the orifice. This difference
requires a deviation from the NFGC
orifice size recommendations. The Sea
Level input should still be reduced by 4%
per thousand ft. and the orifice size must
be selected based on the reduced input
selection shown in Table 12.
ORIFICE ORDERING
INFORMATION
IMPORTANT: Do not plug or drill out
orifices.
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 1:
#60 drill size orifice required
Part # 62-22175-60
Example 2:
1.15mm drill size orifice required
Part # 62-22175-91
ALTERNATE METHOD FOR
CANADIAN
HIGH-
ALTITUDE DERATE
In Canada, unless an orifice change
is specifically mandated by local
codes, an alternate method of altitude
deration through a reduction in
manifold pressure is acceptable as
described in Table 13.
The information in Table 13 is based
on a heating value of 1000 BTU per
cubic feet of natural gas, and 2500
BTU per cubic feet of LP gas.
IMPORTANT: Actual input rates must
be measured on-site with manifold
pressure adjustment to ensure that an
actual 10% reduction in input rate is
achieved.
Once this field adjustment has been
made, the label shown in Figure 46
must be affixed in a conspicuous
location on the front of the furnace
cabinet:
NOTE: This label is supplied in the
information packet shipped with each
furnace.
TABLE 12
IMPORTANT: 90+ MODELS ONLY. DO NOT USE THIS CHART
FOR ANY 80 PLUS MODELS.
LP GAS ORIFICE DRILL SIZE (4% PER 1000 FT DE-RATE)
Altitude Input (per burner) 15000 Orifice Size
0 to 2000 ft 15000 1.15 mm (factory)
2001 to 3000 13200 1.15 mm
3001 to 4000 12600 1.10 mm
4001 to 5000 12000 #58
5001 to 6000 11400 #59
6001 to 7000 10800 #60
7001 to 8000 10200 #62
FIGURE 46
MANIFOLD PRESSURE-CHANGE LABEL
TABLE 13
ALTERNATE METHOD FOR CANADIAN HIGH-ALTITUDE DERATE
IMPORTANT: 90+ MODELS ONLY. DO NOT
USE THIS CHART FOR ANY 80 PLUS MODELS.
NATURAL GAS LP GAS
ALTITUDE
INPUT
OUTPUT
ORIFICE
SIZE
MANIFOLD
PRESSURE
0’ - 2000’
45,000
60,000
75,000
90,000
105,000
120,000
40,500
54,000
67,500
81,000
94,500
108,000
#50
3.5” W.C.
2001’ - 4500’
40,500
54,000
67,500
81,000
94,500
108,000
36,450
48,600
60,750
72,900
85,050
97,200
#51
3.0” W.C.
ALTITUDE
INPUT
OUTPUT
ORIFICE
SIZE
MANIFOLD
PRESSURE
0’ - 2000’
45,000
60,000
75,000
90,000
105,000
120,000
40,500
54,000
67,500
81,000
94,500
108,000
1.15mm
10” W.C.
2001’ - 4500’
40,500
54,000
67,500
81,000
94,500
108,000
36,450
48,600
60,750
72,900
85,050
97,200
1.10mm
7.6” W.C.
THE MANIFOLD PRESSURE OF THIS APPLIANCE HAS
BEEN FIELD ADJUSTED TO OBTAIN THE CORRECT
INPUT RATING FOR INSTALLATION AT ALTITUDES
BETWEEN 2,000 FEET AND 4,500 FEET ELEVATION.
LA PRESSION DU DISTRIBUTEUR D’ALIMENTATION
DE CET APPAREIL A ÉTÉ AJUSTÉ SUR LES LIEUX AFIN
D’OBTENIR LA BONNE PUISSANCE D’ENTRÉE POUR
UNE INSTALLATION ENTRE 2000 ET 4500 PIEDS
D’ALTITUDE.
92-24399-01-01
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