Rheem GF901U Series Installation Instructions Manual page 50

LP GAS AT HIGH ALTITUDE
ELEVATIONS
ORIFICE INSTALLATION
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 Table 7.
TABLE 7
LP GAS ORIFICE DRILL SIZE
(4% PER 1000 FT DE-RATE)
IMPORTANT: 90 Plus Models only. Do not use
this chart for any 80 Plus Models
Input (per
Altitude burner) 15000
0 to 2000 ft. 15000
2000 -3000 13200
3000 -4000 12600
4000 -5000 12000
5000 -6000 11400
6000 -7000 10800
7000 -8000 10200
8000 -9000 9600
9000 -10000 9000
5
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 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 8.
TABLE 8
Orifice Size
ALTERNATE METHOD FOR CANADIAN HIGH-ALTITUDE DERATE
1.15 mm
IMPORTANT: 90 Plus Models only. Do not use this chart for any 80 Plus Models
(factory)
1.15 mm
ALTITUDE INPUT
1.10 mm
45,000
#58
60,000
75,000
#59
0' - 2000'
90,000
105,000
#60
120,000
#62
40,500
54,000
#63
67,500
2001' - 4500'
81,000
#64
94,500
108,000
NATURAL GAS
ORIFICE MANIFOLD
OUTPUT
SIZE PRESSURE
40,500
54,000
67,500
#50 3.5" W.C.
81,000
94,500
108,000
36,450
48,600
60,750
#50 3.0" W.C.
72,900
85,050
97,200
FIGURE 46
MANIFOLD PRESSURE-CHANGE LABEL
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.
The information in Table 8 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.
LP GAS
ORIFICE
ALTITUDE INPUT OUTPUT
SIZE
45,000 40,500
60,000 54,000
75,000 67,500
0' - 2000' 1.15mm
90,000 81,000
105,000 94,500
120,000 108,000
40,500 36,450
54,000 48,600
67,500 60,750
2001' - 4500' 1.15mm
81,000 72,900
94,500 85,050
108,000 97,200
92-24399-01-01
MANIFOLD
PRESSURE
10" W.C.
7.6" W.C.