6 720 644 942 (2014/11) 520 HN
18 | Installation instructions
GAS LINE SIZING
The gas supply piping should be sized according to the applicable code for a maximum draw of 117,000 BTUH. Measure the length
of gas supply line and use the tables in Fig. 14 or the gas line manufacturer’s sizing tables to determine the pipe diameter necessary
to accommodate the BTU demand of the unit. If there are more gas appliances drawing on the same line, size the gas line according
to the total maximum amount of BTU draw for all appliances.
Note: Under sizing the gas line may result in diminished output. See chapter 3.7 for the procedure to measure gas pressure.
FOR NATURAL GAS
Maximum Capacity of pipe in Cubic Feet of Gas per Hour for Gas Pressure of 0.5 Psig or less and a Pressure drop of 0.3 in Water
Column (0.75mbar).(Based on a 0.60 Specific Gravity Gas) Btu numbers given in thousands.
Copper tubing is prohibited for use with Natural Gas in the Commonwealth of Massachusetts and not recommended elsewhere.
Follow boxed numbers for piping just one 520 HN (example: ¾” B.I. Natural Gas pipe for 20 ft (6.1m). will handle 190,000 btu’s
(55.7 kWh). For multiple appliances combine the total btu input load and then refer to applicable chart below.
* EHD = Equivalent Hydraulic Diameter. The greater the value EHD, the greater the gas capacity of the tubing.
Lenght of Black Iron Pipe, Feet
Nominal
Iron
Pipe
Size
Inches
Internal
Diameter
inches
10 20 30 40 50 60 70 80 90 100 125 150 175 200
3/4 0.824 278 190 152 130 115 105 96 90 84 79 72 64 59 55
1 1.049 520 350 285 245 215 195 180 170 160 150 130 120 110 100
1 - 1/4 1.380 1050 730 590 500 440 400 370 350 320 305 275 250 225 210
Table 7
Tube
size,
Inches
EHD*
Lenght of Flexible Corrugated Stainless Steel Tubing (CSST), Feet
10 20 30 40 50 60
1/2 18 82 58 47 41 37 34
3/4 23 161 116 96 83 75 68
1 30 330 231 188 162 144 131
1 - 1/4 37 639 456 374 325 292 267
Table 8
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