Rheem 801S Series Installation Instructions Manual page 36

TABLE 8
SUPPLEMENTAL ORIFICE SIZE CHART
NATURAL GAS ORIFICE SELECTION BASED ON HEATING VALUE & ELEVATION*
Notes:
1. All (-)80+ units are factory equiped with orifices sized for 1050 sea level heating value gas.
2. Local utilities adjust the sea level heating value of gasses used at higher elevations to compensate for appliance operation at altitude.
Installer must be aware of the local heating value (sea level standard) to use the chart below.
3. This chart is based on the National Fuel Gas Code (NFGC) Annex F based on natural gas with a secific gravity of 0.60
4. The recommended orifices below allow the furnace to operate within 10% of design rate. However, NFGC calculations are the best
method.
5. Furnace operation is optimized when operating at design rate. Installer is responsible to verify rate.
6. This table applies to 80+ models only with 25,000BTU/Burner. DO NOT USE THIS CHART FOR ANY 90+ FURNACE MODEL.
Grey Cells Indicate Factory
Orifice Size
1,000-1,100
Gas Heating
900-999
Value
3
(BTU's/ft )
@ Sea
800-899
Level**
700-799
*Table is derived from Appendix of the National Fuel Gas Code . To determine the correct orifice for your installation consult the National
Fuel Gas Code tables F.1 and F.4
**Be sure to use sea level heating value. When requesting the heating value from a local utility, it must be converted to sea level equivalent
in order to use this table.
36
Sea Level 2,000' to 3,000' to
to 1,999' 2,999' 3,999'
43 44 44
42 42 43
42 42 43
41 42 42
40 42
41
39 40 41
38 39 40
37
38 39
37 38 39
36
37 38
35
36 36
ELEVATION
4,000' to 5,000' to 6,000' to
4,999' 5,999' 6,999'
44 45 45
43 43 44
43 43 44
42 43 43
42 42 43
41 42 42
41 41 42
39 40 41
39 40 41
38 39 40
37 37 38
7,000' to 8,000' to 9,000' to
7,999' 8,999' 9,999'
46 47 47
44 45 46
44 45 46
44 44 45
43 44 44
43 43 44
42 43 43
42 42 43
42 42 43
41 41 42
39 40 41
10,000'
48
47
47
46
45
44
44
43
43
43
42