Maximum Capacity of Pipe in Cubic Feet of Natural Gas per Hour for Gas Pressures of
8
FIGURE 2.7: GAS PIPE SIZING TABLES & EXAMPLE
Example: Boiler Model GB200-4H is to be installed. The distance from the existing gas meter to the installation site is 30
ft. What pipe size must be used? The local utility indicates the heating value of natural gas being supplied is 1000 Btu per
cu.ft. Determine cubic feet of gas per hour for above boiler model:
135,000 Btu per hour
= 135 cu.ft. per hour
1000 Btu per cu.ft.
1. Find 30 ft. in upper portion of the table for natural gas under "Length of Pipe, Feet" heading.
2. Moving down the column, match required capacity. Higher capacity is acceptable. In our case it is 152 cu.ft.
3. Move to left-hand column "Nominal Iron Pipe Size, Inches," to read required pipe size. In our case it is 3/4".
Minimum pressure required at the gas valve inlet is 5" W.C.
for natural gas and 11" W.C. for propane. Maximum pressure
allowable at the gas valve inlet is 12" W.C. If the gas pres-
sure is above these limits, a pressure regulator must be
installed. If the gas pressure is below these limits, contact the
local utility.
Testing Gas Piping
For any pressure testing in excess of 1/2 psi, the boiler and
its individual shutoff valve must be isolated from the piping
system by disconnecting them and capping the outlet(s). For
any pressure testing equal to or less than 1/2 psi, the boiler
must be isolated from the piping system by closing its manu-
al shutoff valve.
DANGER: Before placing gas piping into service,
carefully test it to assure every joint is gas tight. Bub-
ble test all joints with a soap solution. NEVER TEST
WITH AN OPEN FLAME AS FIRE OR EXPLOSION
WILL RESULT.
