Page 850 - 2018_IRC

APPENDIX A

meter to the farthest remote appliance is only used to size the adequate for the calculated gas load and that the
initial parts of the overall piping system. The Branch Length required pressure drop (across the regulator) for that
3
Method is applied in the following manner: capacity does not exceed / psi (5.2 kPa) for a 2 psi
4
(1) Determine the gas load for each of the connected (13.8 kPa) system. If the pressure drop across the reg-
appliances. ulator is too high (for the connected gas load), select a
(2) Starting from the meter, divide the piping system into larger regulator.
a number of connected segments, and determine the (2) Measure the distance from the meter to the line regu-
length and amount of gas that each segment would lator located inside the building.
carry assuming that all appliances were operated (3) If there are multiple line regulators, measure the dis-
simultaneously. An allowance (in equivalent length of tance from the meter to the regulator farthest removed
pipe) as determined from Table A.2.2 should be con- from the meter.
sidered for piping segments that include four or more (4) The maximum allowable pressure drop for the 2 psi
fittings. (13.8 kPa) section is 1 psi (6.9 kPa).
(3) Determine the distance from the outlet of the gas (5) Referring to the appropriate sizing table (based on
meter to the appliance farthest removed from the piping material) for 2 psi (13.8 kPa) systems with a 1
meter. psi (6.9 kPa) pressure drop, find this distance in the
(4) Using the longest distance (found in Step 3), size each first column, or the closest larger distance if the exact
piping segment from the meter to the most remote distance is not listed.
appliance outlet. (6) Trace across this row until the gas load is found or the
(5) For each of these piping segments, use the longest closest larger capacity if the exact capacity is not
length and the calculated gas load for all of the con- listed.
nected appliances for the segment and begin the siz- (7) Read up the table column to the top row and select the
ing process in Steps 6 through 8. appropriate pipe size.
(6) Referring to the appropriate sizing table (based on (8) If there are multiple regulators in this portion of the
operating conditions and piping material), find the piping system, each line segment must be sized for its
longest length distance in the first column or the next actual gas load, but using the longest length previ-
larger distance if the exact distance is not listed. The ously determined in steps 2 and 3.
use of alternative operating pressures or pressure
drops will require the use of a different sizing table, The low pressure section (all piping downstream of the
but will not alter the sizing methodology. In many line regulator) is sized as follows:
cases, the use of alternative operating pressures or (1) Determine the gas load for each of the connected
pressure drops will require the approval of both the appliances.
code official and the local gas serving utility. (2) Starting from the line regulator, divide the piping sys-
(7) Trace across this row until the gas load is found or the tem into a number of connected segments or indepen-
closest larger capacity if the exact capacity is not dent parallel piping segments, and determine the
listed. amount of gas that each segment would carry assum-
ing that all appliances were operated simultaneously.
(8) Read up the table column and select the appropriate
pipe size in the top row. Repeat Steps 6, 7 and 8 for An allowance (in equivalent length of pipe) as deter-
each pipe segment in the longest run. mined from Table A.2.2 should be considered for pip-
ing segments that include four or more fittings.
(9) Size each remaining section of branch piping not pre-
viously sized by measuring the distance from the gas (3) For each piping segment, use the actual length or lon-
meter location to the most remote outlet in that gest length (if there are sub-branchlines) and the cal-
branch, using the gas load of attached appliances and culated gas load for that segment and begin the sizing
following the procedures of Steps 2 through 8. process as follows:
(a) Referring to the appropriate sizing table (based
A.3.3 Hybrid pressure method. The sizing of a 2 psi (13.8 on operating pressure and piping material),
kPa) gas piping system is performed using the traditional find the longest length distance in the first col-
Longest Length Method but with modifications. The 2 psi umn or the closest larger distance if the exact
(13.8 kPa) system consists of two independent pressure distance is not listed. The use of alternative
zones, and each zone is sized separately. The Hybrid Pressure operating pressures or pressure drops will
Method is applied as follows: require the use of a different sizing table, but
The sizing of the 2 psi (13.8 kPa) section (from the meter will not alter the sizing methodology. In many
to the line regulator) is as follows: cases, the use of alternative operating pressures
(1) Calculate the gas load (by adding up the name plate or pressure drops can require the approval of
ratings) from all connected appliances. (In certain cir- the code official.
cumstances the installed gas load can be increased up (b) Trace across this row until the appliance gas
to 50 percent to accommodate future addition of load is found or the closest larger capacity if
appliances.) Ensure that the line regulator capacity is the exact capacity is not listed.

2018 INTERNATIONAL RESIDENTIAL CODE ® 825
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