44
SETTING INPUT RATE
The furnace is shipped from the factory with #42 orifices .
They are sized for natural gas having a heating value of
1050 BTU/cu . ft . and a specific gravity of .60 .
Since heating values vary geo-graphically, the manifold
pressure and/or gas orifice size may need to be changed
to adjust the furnace to its nameplate input . Consult the
local gas utility to obtain the yearly average heating value
and orifice size required to fire each individual burner at
25,000 BTU/HR .
NOTE: Refer to the High Altitude Section of this manual
and the National Fuel Gas Code for high altitude rate ad-
justment above 2,000 ft .
TIMING DIAGRAM, FIELD SELECTIONS &
ADJUSTMENTS
Field Selections
TABLE 11
METER TIME
METER TIME IN MINUTES AND SECONDS FOR NORMAL INPUT RATING OF FURNACES EQUIPPED FOR NATURAL
GAS OR L .P .
INPUT
(BTU/HR)
50,000
75,000
100,000
125,000
150,000
ONE
TEN
ONE
TEN
ONE
TEN
ONE
TEN
ONE
TEN
Formula: Input BTU/HR = Heating Value of Gas (BTU/ft
3
) × 3600 x correction factor
Formula: Input BTU/HR =
Time (in seconds) for 1 cubic ft of Gas
METER SIZE
(FT
3
/REV)
HEATING VALUE OF GAS (BTU/FT
3
)
900
1000
1040
1100
2500
MIN SEC MIN SEC MIN SEC MIN SEC MIN SEC
1
5
1
12
1
15
1
19
3
0
10 48 12 0 12 29 13 12 30 0
0 43 0 48 0 50 0 53 2 0
7
12
8
0
8
19
8
48 20
0
0 32 0 36 0 37 0 40 1 30
5
24
6
0
6
14
6
36 15
0
0 26 0 29 0 30 0 32 1 12
4 19 4 48 4 60 5 17 12 0
0 22 0 24 0 25 0 26 1 0
3
36
4
0
4
10
4
24 10
0
Summary of Contents for 801C Series
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