Building Design and Construction Handbook - Merritt - Ventech!

14.50 SECTION FOURTEEN
Besides municipal codes governing design and installation of gas piping and
devices, the gas utility serving the area will usually have a number of regulations
that must be followed. Typically, meters are required to be installed outside the
building. The gas supply should not enter the building from below grade unless
certain venting requirements are met, and gas pressure regulators installed inside
the building must be vented to the outdoors. The local authorities and gas utility
should be consulted as to special regulations relating to the installation of the gas
piping system.
14.23 GAS-PIPE SIZES
Gas piping must be designed to provide enough gas to appliances without excessive
pressure loss between the appliance and the meter. It is customary to size gas piping
so the pressure loss between the meter and any appliance does not exceed 0.3 in
of water during periods of maximum gas demand. Other factors influencing the
pipe size include maximum gas consumption anticipated, length of pipe and number
of fittings, specific gravity of the gas, and the diversity factor.
(C. M. Harris, ‘‘Handbook of Utilities and Services for Buildings,’’ McGraw-
Hill Publishing Company, New York.)
14.24 ESTIMATING GAS CONSUMPTION
Use the manufacturer’s Btu rating of the appliances and the heating value of the
gas to determine the flow required, ft 3 /hr. When Btu ratings are not immediately
available, the values in Table 14.14 may be used for preliminary estimates. The
average heating value of gas in the area can be obtained from the local gas company,
but when this is not immediately available, the values in Table 14.15 can be used
for preliminary estimates.
Example. A building has two 50-gal storage hot-water heaters and 10 domestic
ranges. What is the maximum gas consumption that must be provided for if gas
with a net heating value of 500 Btu/ft 3 is used?
Solution. From Table 14.14,
Heat input � 2(55,000) � 10(65,000) � 760,000 Btu/hr
Maximum gas consumption is therefore 760,000/500 � 1520 ft 3 /hr. The supply
piping would be sized for this flow, even though all appliances would rarely operate
at the same time.
(C. M. Harris, ‘‘Handbook of Utilities and Services for Buildings,’’ and H. E.
Bovay, Jr., ‘‘Handbook of Mechanical and Electrical Systems for Buildings,’’ Mc-
Graw-Hill Publishing Company, New York.)