*(This appendix is informative and is not part of the code.)**piping*system is to make sure that there is sufficient gas pressure at the inlet to each

*appliance*. The majority of systems are residential and the appliances will all have the same, or nearly the same, requirement for minimum gas pressure at the

*appliance*inlet. This pressure will be about 5-inch water column (w.c.) (1.25 kPa), which is enough for proper operation of the

*appliance*regulator to deliver about 3.5-inches water column (w.c.) (875 kPa) to the burner itself. The pressure drop in the

*piping*is subtracted from the source delivery pressure to verify that the minimum is available at the

*appliance.*

There are other systems, however, where the required inlet pressure to the different appliances may be quite varied. In such cases, the greatest inlet pressure required must be satisfied, as well as the farthest *appliance*, which is almost always the critical *appliance *in small systems.

There is an additional requirement to be observed besides the capacity of the system at 100-percent flow. That requirement is that at minimum flow, the pressure at the inlet to any *appliance *does not exceed the pressure rating of the *appliance *regulator. This would seldom be of concern in small systems if the source pressure is ^{1}/_{2} psi (14-inch w.c.) (3.5 kPa) or less but it should be verified for systems with greater gas pressure at the point of supply.

To determine the size of *piping *used in a gas *piping *system, the following factors must be considered:

*point of delivery*to

*appliance*.

*piping*and number of fittings.

For any gas *piping *system, or special *appliance*, or for conditions other than those covered by the tables provided in this code, such as longer runs, greater gas demands or greater pressure drops, the size of each gas *piping* system should be determined by standard engineering practices acceptable to the code official.

*outlet*should be determined, whenever possible, directly from the manufacturer’s gas input Btu/h rating of the

*appliance*that will be installed adjusted for altitude where appropriate. In the case where the ratings of the appliances to be installed are not known, Table 402.2 shows the approximate consumption (in Btu per hour) of certain types of typical household appliances.

*piping*run with four or more fittings (see Table A.2.2).

TABLE A.2.2

EQUIVALENT LENGTHS OF PIPE FITTINGS AND VALVES

SCREWED FITTINGS^{1} | 90° WELDING ELBOWS AND SMOOTH BENDS^{2} | ||||||||||

45°/Ell | 90°/Ell | 180°close returnbends | Tee | R/d = 1 | R/d = 1^{1}/_{3} | R/d = 2 | R/d = 4 | R/d = 6 | R/d = 8 | ||

k factor = | 0.42 | 0.90 | 2.00 | 1.80 | 0.48 | 0.36 | 0.27 | 0.21 | 0.27 | 0.36 | |

L/d' ratio^{4} n = | 1 4 | 30 | 67 | 60 | 16 | 12 | 9 | 7 | 9 | 12 | |

Nominalpipe size, inches | Inside diameter d, inches, Schedule 40 ^{6} | L = Equivalent Length In Feet of Schedule 40 (Standard-weight) Straight Pipe^{6} | |||||||||

^{1}/_{2} | 0.622 | 0.73 | 1.55 | 3.47 | 3.10 | 0.83 | 0.62 | 0.47 | 0.36 | 0.47 | 0.62 |

3/4 | 0.824 | 0.96 | 2.06 | 4.60 | 4.12 | 1.10 | 0.82 | 0.62 | 0.48 | 0.62 | 0.82 |

1 | 1.049 | 1.22 | 2.62 | 5.82 | 5.24 | 1.40 | 1.05 | 0.79 | 0.61 | 0.79 | 1.05 |

1^{1}/4 | 1.380 | 1.61 | 3.45 | 7.66 | 6.90 | 1.84 | 1.38 | 1.03 | 0.81 | 1.03 | 1.38 |

1^{1}/_{2} | 1.610 | 1.88 | 4.02 | 8.95 | 8.04 | 2.14 | 1.61 | 1.21 | 0.94 | 1.21 | 1.61 |

2 | 2.067 | 2.41 | 5.17 | 11.5 | 10.3 | 2.76 | 2.07 | 1.55 | 1.21 | 1.55 | 2.07 |

2^{1}/_{2} | 2.469 | 2.88 | 6.16 | 13.7 | 12.3 | 3.29 | 2.47 | 1.85 | 1.44 | 1.85 | 2.47 |

3 | 3.068 | 3.58 | 7.67 | 17.1 | 15.3 | 4.09 | 3.07 | 2.30 | 1.79 | 2.30 | 3.07 |

4 | 4.026 | 4.70 | 10.1 | 22.4 | 20.2 | 5.37 | 4.03 | 3.02 | 2.35 | 3.02 | 4.03 |

5 | 5.047 | 5.88 | 12.6 | 28.0 | 25.2 | 6.72 | 5.05 | 3.78 | 2.94 | 3.78 | 5.05 |

6 | 6.065 | 7.07 | 15.2 | 33.8 | 30.4 | 8.09 | 6.07 | 4.55 | 3.54 | 4.55 | 6.07 |

8 | 7.981 | 9.31 | 20.0 | 44.6 | 40.0 | 10.6 | 7.98 | 5.98 | 4.65 | 5.98 | 7.98 |

10 | 10.02 | 11.7 | 25.0 | 55.7 | 50.0 | 13.3 | 10.0 | 7.51 | 5.85 | 7.51 | 10.0 |

12 | 11.94 | 13.9 | 29.8 | 66.3 | 59.6 | 15.9 | 11.9 | 8.95 | 6.96 | 8.95 | 11.9 |

14 | 13.13 | 15.3 | 32.8 | 73.0 | 65.6 | 17.5 | 13.1 | 9.85 | 7.65 | 9.85 | 13.1 |

16 | 15.00 | 17.5 | 37.5 | 83.5 | 75.0 | 20.0 | 15.0 | 11.2 | 8.75 | 11.2 | 15.0 |

18 | 16.88 | 19.7 | 42.1 | 93.8 | 84.2 | 22.5 | 16.9 | 12.7 | 9.85 | 12.7 | 16.9 |

20 | 18.81 | 22.0 | 47.0 | 105.0 | 94.0 | 25.1 | 18.8 | 14.1 | 11.0 | 14.1 | 18.8 |

24 | 22.63 | 26.4 | 56.6 | 126.0 | 113.0 | 30.2 | 22.6 | 17.0 | 13.2 | 17.0 | 22.6 |

*(continued)*

TABLE A.2.2—continued

EQUIVALENT LENGTHS OF PIPE FITTINGS AND VALVES

MITER ELBOWS^{3} (No. of miters) | WELDING TEES | VALVES (screwed, flanged, or welded) | ||||||||||

1-45° | 1-60° | 1-90° | 2-90°^{5} | 3-90°^{5} | Forged | Miter^{3} | Gate | Globe | Angle | Swing Check | ||

k factor = | 0.45 | 0.90 | 1.80 | 0.60 | 0.45 | 1.35 | 1.80 | 0.21 | 10 | 5.0 | 2.5 | |

L/d' ratio^{4} n = | 15 | 30 | 60 | 20 | 15 | 45 | 60 | 7 | 333 | 167 | 83 | |

Nominal pipe size, inches | Inside diameter d, inches, Schedule 40 ^{6} | L = Equivalent Length In Feet of Schedule 40 (Standard-weight) Straight Pipe^{6} | ||||||||||

^{1}/_{2} | 0.622 | 0.78 | 1.55 | 3.10 | 1.04 | 0.78 | 2.33 | 3.10 | 0.36 | 17.3 | 8.65 | 4.32 |

^{3}/_{4} | 0.824 | 1.03 | 2.06 | 4.12 | 1.37 | 1.03 | 3.09 | 4.12 | 0.48 | 22.9 | 11.4 | 5.72 |

1 | 1.049 | 1.31 | 2.62 | 5.24 | 1.75 | 1.31 | 3.93 | 5.24 | 0.61 | 29.1 | 14.6 | 7.27 |

1^{1}/_{4} | 1.380 | 1.72 | 3.45 | 6.90 | 2.30 | 1.72 | 5.17 | 6.90 | 0.81 | 38.3 | 19.1 | 9.58 |

1^{1}/_{2} | 1.610 | 2.01 | 4.02 | 8.04 | 2.68 | 2.01 | 6.04 | 8.04 | 0.94 | 44.7 | 22.4 | 11.2 |

2 | 2.067 | 2.58 | 5.17 | 10.3 | 3.45 | 2.58 | 7.75 | 10.3 | 1.21 | 57.4 | 28.7 | 14.4 |

2^{1}/_{2} | 2.469 | 3.08 | 6.16 | 12.3 | 4.11 | 3.08 | 9.25 | 12.3 | 1.44 | 68.5 | 34.3 | 17.1 |

3 | 3.068 | 3.84 | 7.67 | 15.3 | 5.11 | 3.84 | 11.5 | 15.3 | 1.79 | 85.2 | 42.6 | 21.3 |

4 | 4.026 | 5.04 | 10.1 | 20.2 | 6.71 | 5.04 | 15.1 | 20.2 | 2.35 | 112.0 | 56.0 | 28.0 |

5 | 5.047 | 6.30 | 12.6 | 25.2 | 8.40 | 6.30 | 18.9 | 25.2 | 2.94 | 140.0 | 70.0 | 35.0 |

6 | 6.065 | 7.58 | 15.2 | 30.4 | 10.1 | 7.58 | 22.8 | 30.4 | 3.54 | 168.0 | 84.1 | 42.1 |

8 | 7.981 | 9.97 | 20.0 | 40.0 | 13.3 | 9.97 | 29.9 | 40.0 | 4.65 | 22.0 | 111.0 | 55.5 |

10 | 10.02 | 12.5 | 25.0 | 50.0 | 16.7 | 12.5 | 37.6 | 50.0 | 5.85 | 278.0 | 139.0 | 69.5 |

12 | 11.94 | 14.9 | 29.8 | 59.6 | 19.9 | 14.9 | 44.8 | 59.6 | 6.96 | 332.0 | 166.0 | 83.0 |

14 | 13.13 | 16.4 | 32.8 | 65.6 | 21.9 | 16.4 | 49.2 | 65.6 | 7.65 | 364.0 | 182.0 | 91.0 |

16 | 15.00 | 18.8 | 37.5 | 75.0 | 25.0 | 18.8 | 56.2 | 75.0 | 8.75 | 417.0 | 208.0 | 104.0 |

18 | 16.88 | 21.1 | 42.1 | 84.2 | 28.1 | 21.1 | 63.2 | 84.2 | 9.85 | 469.0 | 234.0 | 117.0 |

20 | 18.81 | 23.5 | 47.0 | 94.0 | 31.4 | 23.5 | 70.6 | 94.0 | 11.0 | 522.0 | 261.0 | 131.0 |

24 | 22.63 | 28.3 | 56.6 | 113.0 | 37.8 | 28.3 | 85.0 | 113.0 | 13.2 | 629.0 | 314.0 | 157.0 |

**Note:**Values for welded fittings are for conditions where bore is not obstructed by weld spatter or backing rings. If appreciably obstructed, use values for “Screwed Fittings.”

*relation*(

*n*-

*k*/4ƒ’).

^{1}/

_{2}

*d*.

*n*values.

*Piping Handbook*, 4th ed., Table XIV, pp. 100-101. Copyright 1945 by McGraw-Hill, Inc. Used by permission of McGraw-Hill Book Company.

^{1}/

_{2}pounds per square inch (psi) (3.5 kPa) and pressure drops greater than 0.5-inch w.c. (125 Pa). In using these tables, an allowance (in equivalent length of pipe) should be considered for any

*piping*run with four or more fittings [see Table A.2.2].

*piping*systems that are to be supplied with gas of a specific gravity of 0.70 or less can be sized directly from the tables provided in this code, unless the code official specifies that a gravity factor be applied. Where the specific gravity of the gas is greater than 0.70, the gravity factor should be applied.

TABLE A.2.4

MULTIPLIERS TO BE USED WITH TABLES 402.4(1)

THROUGH 402.4(22) WHERE THE SPECIFIC GRAVITY

OF THE GAS IS OTHER THAN 0.60

SPECIFIC GRAVITY | MULTIPLIER | SPECIFIC GRAVITY | MULTIPLIER |

0.35 | 1.31 | 1.00 | 0.78 |

0.40 | 1.23 | 1.10 | 0.74 |

0.45 | 1.16 | 1.20 | 0.71 |

0.50 | 1.10 | 1.30 | 0.68 |

0.55 | 1.04 | 1.40 | 0.66 |

0.60 | 1.00 | 1.50 | 0.63 |

0.65 | 0.96 | 1.60 | 0.61 |

0.70 | 0.93 | 1.70 | 0.59 |

0.75 | 0.90 | 1.80 | 0.58 |

0.80 | 0.87 | 1.90 | 0.56 |

0.85 | 0.84 | 2.00 | 0.55 |

0.90 | 0.82 | 2.10 | 0.54 |

*piping*system to the maximum value.

*piping*in a system within the range of the capacity tables, proceed as follows (also see sample calculations included in this Appendix):

*piping*system into appropriate segments consistent with the presence of tees, branch lines and main runs. For each segment, determine the gas load (assuming all appliances operate simultaneously) and its overall length. An allowance (in equivalent length of pipe) as determined from Table A.2.2 shall be considered for

*piping*segments that include four or more fittings.

*appliance*to be attached to the

*piping*system. Where Tables 402.4(1) through 402.4(24) are to be used to select the

*piping*size, calculate the gas demand in terms of cubic feet per hour for each

*piping*system

*outlet*. Where Tables 402.4(25) through 402.4(36) are to be used to select the

*piping*size, calculate the gas demand in terms of thousands of Btu per hour for each

*piping*system

*outlet*.

*piping*system is for use with other than undiluted liquefied petroleum gases, determine the design system pressure, the allowable loss in pressure (pressure drop), and specific gravity of the gas to be used in the

*piping*system.

*piping*from the

*point of delivery*to the most remote

*outlet*in the building/

*piping*system.

*piping*. If the gravity factor is to be applied, the values in the selected row of the table are multiplied by the appropriate multiplier from Table A.2.4.

*outlet*, find the gas demand for that

*outlet*in the horizontal row just selected. If the exact figure of demand is not shown, choose the next larger figure left in the row.

*piping*will be found.

*outlet*and each section of gas

*piping*. For each section of

*piping*, determine the total gas demand supplied by that section.

*piping*components (such as elbows, tees and valves) are installed in a pipe run, additional pressure loss can be accounted for by the use of equivalent lengths. Pressure loss across any

*piping*component can be equated to the pressure drop through a length of pipe. The equivalent length of a combination of only four elbows/tees can result in a jump to the next larger length row, resulting in a significant reduction in capacity. The equivalent lengths in feet shown in Table A.2.2 have been computed on a basis that the inside diameter corresponds to that of Schedule 40 (standard-weight) steel pipe, which is close enough for most purposes involving other schedules of pipe. Where a more specific solution for equivalent length is desired, this may be made by multiplying the actual inside diameter of the pipe in inches by

*n*/12, or the actual inside diameter in feet by

*n*(

*n*can be read from the table heading). The equivalent length values can be used with reasonable accuracy for copper or brass fittings and bends although the resistance per foot of copper or brass pipe is less than that of steel. For copper or brass valves, however, the equivalent length of pipe should be taken as 45 percent longer than the values in the table, which are for steel pipe.

*appliance*is only used to size the initial parts of the overall

*piping*system. The Branch Length Method is applied in the following manner:

*piping*system into a number of connected segments, and determine the length and 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.

*outlet*of the gas meter to the

*appliance*furthest removed from the meter.

*piping*segment from the meter to the most remote

*appliance outlet*.

*piping*segments, use the longest length and the calculated gas load for all of the connected appliances for the segment and begin the sizing process in Steps 6 through 8.

*piping*material), find the longest length distance in the first column or the next 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 will require the approval of both the code official and the local gas serving utility.

*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:

^{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.

*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.

*piping*system, each line segment must be sized for its actual gas load, but using the longest length previously determined above.

*appliance*within the limitations that are presented to the designer.

*piping*segment, calculate the pressure drop based on pipe size, length as a percentage of 100 feet (30 480 mm) and gas flow. Table A.3.4 shows pressure drop per 100 feet (30 480 mm) for pipe sizes from

^{1}/

_{2}inch (12.7 mm) through 2 inches (51 mm). The sum of pressure drops to the critical

*appliance*is subtracted from the supply pressure to verify that sufficient pressure will be available. If not, the layout can be examined to find the high drop section(s) and sizing selections modified.

**Note:**Other values can be obtained by using the following equation:

Desired Value | = |

^{3}/

_{4}-inch (19.1 mm) pipe at 2 inches/100 feet, multiply the capacity of

^{3}/

_{4}-inch pipe at 1 inch/100 feet by the square root of the pressure ratio:

= | 147 × 1.414 | = | 208 MBH |

*(MBH = 1000 Btu/h)*

TABLE A.3.4

THOUSANDS OF BTU/H (MBH) OF NATURAL GAS PER 100 FEET OF PIPE AT VARIOUS PRESSURE DROPS AND PIPE DIAMETERS

PRESSURE DROP PER 100 FEET IN INCHES W.C. | PIPE SIZES (inch) | |||||

^{1}/_{2} | ^{3}/_{4} | 1 | 1^{1}/_{4} | 1^{1}/_{2} | 2 | |

0.2 | 31 | 64 | 121 | 248 | 372 | 716 |

0.3 | 38 | 79 | 148 | 304 | 455 | 877 |

0.5 | 50 | 104 | 195 | 400 | 600 | 1160 |

1.0 | 71 | 147 | 276 | 566 | 848 | 1640 |

where:

Q | = | Rate, cubic feet per hour at 60°F and 30-inch mercury column |

D | = | Inside diameter of pipe, in. |

P_{1} | = | Upstream pressure, psia |

P_{2} | = | Downstream pressure, psia |

Y | = | Superexpansibility factor = 1/supercompressibility factor |

C_{r} | = | Factor for viscosity, density and temperature* |

Note: See Table 402.4 for *Y *and *C _{r }* for natural gas and propane.

S | = | Specific gravity of gas at 60°F and 30-inch mercury column (0.60 for natural gas, 1.50 for propane), or = 1488μ |

T | = | Absolute temperature, °F or = t + 460 |

t | = | Temperature, °F |

Z | = | Viscosity of gas, centipoise (0.012 for natural gas, 0.008 for propane), or = 1488μ |

ƒba | = | Base friction factor for air at 60°F (CF = 1) |

L | = | Length of pipe, ft |

ΔH | = | Pressure drop, in. w.c. (27.7 in. H_{2}O = 1 psi) |

(For SI, see Section 402.4)

TABLE A.5.1

SCHEDULE 40 STEEL PIPE STANDARD SIZES

NOMINAL SIZE (inch) | INTERNAL DIAMETER (inch) | NOMINAL SIZE (inch) | INTERNAL DIAMETER (inch) |

^{1}/_{4} | 0.364 | 1^{1}/_{2} | 1.610 |

^{3}/_{8} | 0.493 | 2 | 2.067 |

^{1}/_{2} | 0.622 | 2^{1}/_{2} | 2.469 |

^{3}/_{4} | 0.824 | 3 | 3.068 |

1 | 1.049 | 3^{1}/_{2} | 3.548 |

1^{1}/_{4} | 1.380 | 4 | 4.026 |

TABLE A.5.2

COPPER TUBE STANDARD SIZES

TUBE TYPE | NOMINAL OR STANDARD SIZE (inches) | INTERNAL DIAMETER (inches) |

K | ^{1}/_{4} | 0.305 |

L | ^{1}/_{4} | 0.315 |

ACR (D) | ^{3}/_{8} | 0.315 |

ACR (A) | ^{3}/_{8} | 0.311 |

K | ^{3}/_{8} | 0.402 |

L | ^{3}/_{8} | 0.430 |

ACR (D) | ^{1}/_{2} | 0.430 |

ACR (A) | ^{1}/_{2} | 0.436 |

K | ^{1}/_{2} | 0.527 |

L | ^{1}/_{2} | 0.545 |

ACR (D) | ^{5}/_{8} | 0.545 |

ACR (A) | ^{5}/_{8} | 0.555 |

K | ^{5}/_{8} | 0.652 |

L | ^{5}/_{8} | 0.666 |

ACR (D) | ^{3}/_{4} | 0.666 |

ACR (A) | ^{3}/_{4} | 0.680 |

K | ^{3}/_{4} | 0.745 |

L | ^{3}/_{4} | 0.785 |

ACR | ^{7}/_{8} | 0.785 |

K | 1 | 0.995 |

L | 1 | 1.025 |

ACR | 1^{1}/_{8} | 1.025 |

K | 1^{1}/_{4} | 1.245 |

L | 1^{1}/_{4} | 1.265 |

ACR | 1^{3}/_{8} | 1.265 |

K | 1^{1}/_{2} | 1.481 |

L | 1^{1}/_{2} | 1.505 |

ACR | 1^{5}/_{8} | 1.505 |

K | 2 | 1.959 |

L | 2 | 1.985 |

ACR | 2^{1}/_{8} | 1.985 |

K | 2^{1}/_{2} | 2.435 |

L | 2^{1}/_{2} | 2.465 |

ACR | 2^{5}/_{8} | 2.465 |

K | 3 | 2.907 |

L | 3 | 2.945 |

ACR | 3^{1}/_{8} | 2.945 |

*outlet*of the

*piping*system shown in Figure A.6.1, with a designated pressure drop of 0.5-inch w.c. (125 Pa) using the Longest Length Method. The gas to be used has 0.60 specific gravity and a heating value of 1,000 Btu/ft

^{3}(37.5 MJ/m

^{3}).

**Solution:**

*point of delivery*to the most remote

*outlet*(A) is 60 feet (18 288 mm). This is the only distance used.

(4) If a different gravity factor is applied to this example, the values in the row marked 60 feet (18 288 mm) of Table 402.4(2) would be multiplied by the appropriate multiplier from Table A.2.4 and the resulting cubic feet per hour values would be used to size the *piping*.

FIGURE A.6.1

PIPING PLAN SHOWING A STEEL PIPING SYSTEM

*piping*system shown in Figure A.6.2, with a designated pressure drop of 1 psi (6.9 kPa) for the 2 psi (13.8 kPa) section and 3- inch w.c. (0.75 kPa) pressure drop for the 13-inch w.c. (2.49 kPa) section. The gas to be used has 0.60 specific gravity and a heating value of 1,000 Btu/ft

^{3}(37.5 MJ/m

^{3}).

**Solution:**

^{3}/hr).

^{3}/

_{4}psig (5.2 kPa), Table 402.4(18) cannot be used. Note: If pressure drop exceeds

^{3}/

_{4}psi (5.2 kPa), then a larger regulator must be selected or an alternative sizing method must be used.

^{3}/hr)] is 4-inch w.c. (0.99 kPa) based on manufacturer’s performance data.

^{3}/hr) (furnace + water heater + dryer).

Note: It is not unusual to oversize the supply line by 25 to 50 percent of the as-installed load. EHD size 18 has a capacity of 189 cfh (5.35 m^{3}/ hr).

^{3}/hr).

^{3}/hr).

^{3}/hr).

FIGURE A.6.2

PIPING PLAN SHOWING A CSST SYSTEM

*piping*system shown in Figure A.6.3, with a designated pressure drop of 1-inch w.c. (250 Pa) (using the Branch Length Method). The gas to be used has 0.60 specific gravity and a heating value of 1,000 Btu/ft

^{3}(37.5 MJ/m

^{3}).

**Solution:**

*point of delivery*to the most remote

*appliance*is 50 feet (15 240 mm), A + C.

^{3}/hr) for four appliances requires 1-inch tubing.

*point of delivery*to the range/oven at the end of Section B is 30 feet (9144 mm), A + B.

^{3}/hr) for the range/oven requires

^{1}/

_{2}-inch tubing.

*point of delivery*to the dryer at the end of Section C is 50 feet (15 240 mm), A + C.

^{3}/hr) for the dryer requires

^{3}/

_{8}-inch tubing.

*point of delivery*to the water heater at the end of Section D is 30 feet (9144 mm), A + D.

^{3}/hr) for the water heater requires

^{3}/

_{8}-inch tubing.

*point of delivery*to the furnace at the end of Section E is 30 feet (9144 mm), A + E.

^{3}/hr) for the furnace requires

^{1}/

_{2}-inch tubing.

*piping*system shown in Figure A.6.4, with a designated pressure drop of 0.5-inch w.c. (125 Pa) using the branch length method. The gas to be used has 0.60 specific gravity and a heating value of 1,000 Btu/ft

^{3}(37.5 MJ/m

^{3}).

**Solution:**

*point of delivery*to the retrofit

*appliance*(barbecue) at the end of Section G is 40 feet (12 192 mm), A + B + G.

^{3}/hr) for the barbecue requires EHD 18 CSST.

FIGURE A.6.4

PIPING PLAN SHOWING A MODIFICATION

TO EXISTING PIPING SYSTEM

*piping*system is installed on a warm autumn afternoon when the temperature is 70°F (21°C). In accordance with local custom, the new

*piping*system is subjected to an air pressure test at 20 psig (138 kPa). Overnight, the temperature drops and when the inspector shows up first thing in the morning the temperature is 40°F (4°C).

*piping*system is unchanged, then the formula based on Boyle’s and Charles’ law for determining the new pressure at a reduced temperature is as follows:

T_{1} | = | Initial temperature, absolute (T_{1} + 459) |

T_{2} | = | Final temperature, absolute (T_{2} + 459) |

P_{1} | = | Initial pressure, psia (P_{1} + 14.7) |

P_{2} | = | Final pressure, psia (P_{2} + 14.7) |

P_{2} | = | 32.7 - 14.7 |

P_{2} | = | 18 psig |

Therefore, the gauge could be expected to register 18 psig (124 kPa) when the ambient temperature is 40°F (4°C).

*H*= pressure drop, in w.c. (27.7 in. H

_{2}O = 1 psi), proceed as follows:

For ^{1}/_{2}-inch pipe, Δ*H* = ^{20 feet}/_{100 feet} × 0.3 inch w.c. = 0.06 in w.c.

For ^{3}/_{4}-inch pipe, Δ*H* = ^{15 feet}/_{100 feet} × 0.3 inch w.c. = 0.045 in w.c.

For 1 inch pipe: Δ*H* = ^{10 feet}/_{100 feet} × 0.2 inch w.c. = 0.02 in w.c.

For ^{3}/_{4}-inch pipe: Δ*H* = ^{10 feet}/_{100 feet} × [0.5 inch w.c. + ^{(110,000 Btu/hr-104,000 Btu/hr)}/_{(147,000 Btu/hr-104,000 Btu/hr) }× (1.0 inches w.c. - 0.5 inch w.c.)] = 0.1 × 0.57 inch w.c. ≈ 0.06 inch w.c.

*Note that the pressure drop between 104,000 Btu/hr and 147,000 Btu/hr has been interpolated as 110,000 Btu/hr.*

For 1-inch pipe: Δ*H* = ^{20 feet}/_{100 feet} × [0.2 inch w.c. + ^{(14,000 Btu/hr)}/_{(27,000 Btu/hr) }× 0.1 inch w.c.] = 0.05 inch w.c.

For ^{3}/_{4}-inch pipe: Δ*H* = ^{20 feet}/_{100 feet} × 1.0 inch w.c. = 0.2 inch w.c.

*Note that the pressure drop between 121,000 Btu/hr and 148,000 Btu/hr has been interpolated as 135,000 Btu/hr, but interpolation for the 3/4-inch pipe (trivial for 104,000 Btu/hr to 147,000 Btu/hr) was not used.*

For 1-inch pipe: Δ*H* = ^{30 feet}/_{100 feet} × 1.0 inches w.c. = 0.3 inch w.c.

For 1^{1}/_{4}-inch pipe: Δ*H* = ^{30 feet}/_{100 feet} × 0.2 inch w.c. = 0.06 inch w.c.

*Note that interpolation for these options is ignored since the table values are close to the 245,000 Btu/hr carried by that section.*

Minimum pressure drop to farthest *appliance*:

Δ*H* = 0.06 inch w.c. + 0.02 inch w.c. + 0.06 inch w.c. = 0.14 inch w.c.

Larger pressure drop to the farthest *appliance*:

Δ*H* = 0.06 inch w.c. + 0.06 inch w.c. + 0.3 inch w.c. = 0.42 inch w.c.

*Notice that Section 2 and the run to B do not enter into this calculation, provided that the appliances have similar input pressure requirements.*

For SI units: 1 Btu/hr = 0.293 W, 1 cubic foot = 0.028 m^{3}, 1 foot = 0.305 m, 1 inch w.c. = 249 Pa.