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HIGH ALTITUDE DERATE
Units may be installed at altitudes up to 4500 feet (1372 m) above sea level without any modification. At altitudes above 4500
feet (1372 m), units must be derated as shown in table 1.
NOTE - This is the only permissible derate for these units.
TABLE 1. Manifold Pressure Versus Altitude
Natural Gas Propane (LP)
Altitude (ft.)
Heating value*
(BTU/ft
)
Manifold Pressure
(in. w. c.)
Heating value*
(BTU/ft
)
Manifold Pressure
(in. w. c.)
High Low High Low
2000 948 3.50 2.00 2278 10.00 5.60
3000 914 3.50 2.00 2196 10.00 5.60
4000 881 3.50 2.00 2116 10.00 5.60
4500 865 3.50 2.00 2077 10.00 5.60
5000 849 3.29 1.88 2039 9.41 5.38
5500 833 3.27 1.87 2000 9.35 5.34
6000 818 3.25 1.86 1964 9.29 5.31
6500 802 3.23 1.84 1927 9.24 5.28
7000 787 3.21 1.83 1891 9.18 5.25
7500 771 3.19 1.82 1853 9.12 5.21
* Consult local utility for actual heating value.
Furnace input = Input Factor X Nameplate Input
Above 7500 feet, call Lennox Technical Services for additional assistance.
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