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TABLE 2
LP GAS PIPE CAPACITY TABLE (CU. FT./HR.)
Maximum capacity of pipe in thousands of BTU per hour of undiluted liquefied petroleum
gases (at 11 inches water column inlet pressure).
(Based on a Pressure Drop of 0.5 Inch Water Column)
Nominal
Iron Pipe
10
Size, Inches
1/2
275
3/4
567
1
1,071 732
1-1/4
2,205 1,496 1,212 1,039
1-1/2
3,307 2,299 1,858 1,559 1,417 1,275 1,181 1,086 1,023
2
6,221 4,331 3,465 2,992 2,646 2,394 2,205 2,047 1,921 1,811 1,606 1,496
Example (LP): Input BTU requirement of unit, 150,000
Equivalent length of pipe, 60 ft. = 3/4" IPS required.
D. DJUSTING OR CHECKING FURN CE INPUT
– Natural Gas Line Pressure 5" - 10.5" W.C.
– LP Gas Line Pressure 11" - 13" W.C.
– Natural Gas Manifold Pressure 3.5" W.C
– LP Gas Manifold Pressure - 10" W.C.
Supply and manifold pressure taps are located on the gas valve body 1/8" N.P.T.
Use a properly calibrated manometer gauge for accurate gas pressure readings.
Only small variations in the gas flow should be made by means of the pressure regulator
adjustment. Furnaces functioning on LP gas must be set by means of the tank or branch
supply regulators. The furnace manifold pressure should be set at 10" W.C. at the gas con-
trol valve.
To adjust the pressure regulator, remove the regulator cap and turn the adjustment screw
clockwise to increase pressure or counterclockwise to decrease pressure. Then replace
the regulator cap securely.
Any necessary major changes in the gas flow rate should be made by changing the size of
the burner orifices. To change orifice spuds, shut off the manual main gas valve and
remove the gas manifold.
For elevations up to 2,000 feet, rating plate input ratings apply. For high altitudes (elevations
over 2,000 ft.), see conversion kit index 92-21519-47 for derating and orifice spud sizes.
Check of input is important to prevent over-firing of the furnace beyond its design-
rated input. NEVER SET INPUT ABOVE THAT SHOWN ON THE RATING PLATE. Use
the following table or formula to determine input rate.
Heating Value of Gas
(BTU/Cu. Ft.) x 3600
Cu. Ft. Per Hr. Required =
Time in Seconds
(for 1 Cu. Ft.) of Gas
TABLE 3
METER TIME IN MINUTES AND SECONDS FOR NORMAL
INPUT RATING OF FURNACES EQUIPPED FOR NATURAL
METER
INPUT
SIZE
BTU/HR
CU. FT.
ONE
40,000
TEN
ONE
60,000
TEN
ONE
80,000
TEN
ONE
100,000
TEN
Length of Pipe, Feet
20
30
40
50
60
70
80
189
152
129
114
103
96
89
393
315
267
237
217
196
182
590
504
448
409
378
346
913
834
771
724
OR LP GAS
HEATING VALUE OF GAS BTU PER CU. FT.
900
1000
1040
MIN. SEC. MIN. SEC. MIN. SEC. MIN. SEC. MIN. SEC.
1
21
1
30
1
34
13
30 15
0 15
36 16
0
54
1
0
1
3
9
0 10
0 10
24
0
41
0
45
0
47
6
45
7
30
7
48
0
33
0
36
0
38
5
24
6
0
6
15
90 100 125 150
83
78
69
63
173
162
146 132
322
307
275 252
677
630
567 511
976
866 787
1100
2500
1
39
3
45
30
37
30
1
6
2
30
11
0
25
0
0
50
1
53
8
15
18
45
0
40
1
30
6
36
15
0
23
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