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# A.3.3 Hybrid Pressure Method

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The sizing of a 2 psi (13.8
kPa) gas

The sizing of the 2 psi (13.8 kPa) section (from the meter to the line regulator) is as follows:

*piping*system is performed using the traditional Longest Length Method but with modifications. The 2 psi (13.8 kPa) system consists of two independent pressure zones, and each zone is sized separately. The Hybrid Pressure Method is applied as follows:

The sizing of the 2 psi (13.8 kPa) section (from the meter to the line regulator) is as follows:

- Calculate the gas load (by adding up the name plate
ratings) from all connected appliances. (In certain
circumstances the installed gas load can be increased
up to 50 percent to accommodate future addition of
appliances.) Ensure that the line regulator capacity is
adequate for the calculated gas load and that the
required pressure drop (across the regulator) for that
capacity does not exceed
^{3}/_{4}psi (5.2 kPa) for a 2 psi (13.8 kPa) system. If the pressure drop across the regulator is too high (for the connected gas load), select a larger regulator. - Measure the distance from the meter to the line regulator located inside the building.
- If there are multiple line regulators, measure the distance from the meter to the regulator furthest removed from the meter.
- The maximum allowable pressure drop for the 2 psi (13.8 kPa) section is 1 psi (6.9 kPa).
- Referring to the appropriate sizing table (based on
*piping*material) for 2 psi (13.8 kPa) systems with a 1 psi (6.9 kPa) pressure drop, find this distance in the first column, or the closest larger distance if the exact distance is not listed. - Trace across this row until the gas load is found or the closest larger capacity if the exact capacity is not listed.
- Read up the table column to the top row and select the appropriate pipe size.
- If there are multiple regulators in this portion of the
*piping*system, each line segment must be sized for its actual gas load, but using the longest length previously determined above.

*piping*downstream of the line regulator) is sized as follows:

- Determine the gas load for each of the connected appliances.
- Starting from the line regulator, divide the piping system into a number of connected segments or independent parallel piping segments, and determine the amount of gas that each segment would carry assuming that all appliances were operated simultaneously. An allowance (in equivalent length of pipe) as determined from Table A.2.2 should be considered for piping segments that include four or more fittings.
- For each piping segment, use the actual length or
longest length (if there are sub-branchlines) and the
calculated gas load for that segment and begin the
sizing process as follows:
- Referring to the appropriate sizing table (based on operating pressure and piping material), find the longest length distance in the first column or the closest larger distance if the exact distance is not listed. The use of alternative operating pressures and/or pressure drops will require the use of a different sizing table, but will not alter the sizing methodology. In many cases, the use of alternative operating pressures and/or pressure drops can require the approval of the code official.
- Trace across this row until the appliance gas load is found or the closest larger capacity if the exact capacity is not listed.
- Read up the table column to the top row and select the appropriate pipe size.
- Repeat this process for each segment of the piping system.

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