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Designing Copper Fuel Gas Systems
Using good engineering practice, a system can be optimally designed using the smallest allowable size of tube that will supply gas to the appliance with appropriate volume and pressure.
For a single-family dwelling, the gas company will frequently install the meter outdoors and terminate its facilities with a 1" NPS (Nominal Pipe Size) threaded connection outside the building. The transition to copper tube can either be made at that point or a " (or larger) NPS steel pipe can be extended through the exterior wall and the transition to copper made inside the building (as shown in Figure 3). In either case, care should be taken to ensure that the copper tube is not used to support the meter or exterior piping. This can be accomplished by anchoring the meter or the steel pipe passing through the exterior wall. Some gas companies will set the meter with a brace or bracket and run copper tube through to the outside so service personnel are aware that it is a semirigid system and damage can be avoided.
The connection between the steel system and copper system does not create a corrosion concern if the connection is made in a dry location or a location that does not allow moisture to collect at the connection. The absence of continuous moisture prevents the occurrence of galvanic action and subsequent corrosion of the steel pipe.
There are two basic types of piping layouts. One uses a main run with branch lines to supply gas to the various appliances. The other employs individual runs to each appliance from a gas distribution manifold installed between the meter and the appliances, as shown in Figure 4. Depending on the building being supplied, a combination of these two systems may also be used.
A typical layout for an apartment complex is shown in Figure 5. This system uses a space heater (or a combined heating-cooling unit) for each apartment or condominium. The use of copper tube provides simpler, more economical installation of meter banks to provide individual metering. A typical method of providing banks or groups of meters for a multi-family building is shown in Figure 6.
A low pressure house layout with branch runs is shown in Figure 7, and one with individual runs is shown in Figure 8. Typical combination layouts, elevated and low pressure, are shown in Figures 9 through 12. Figures 9 and 10 show single-regulated systems with either branched or individual runs. Figures 11 and 12 show multiple-regulated systems of the same configuration.