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Gas pipe sizing

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  • Gas pipe sizing

    Is there an easy way to size gas pipe. I'm seriously spinning my wheels on this. I'm replumbing most of a 4500 square ft. home with two tankless units, furnace , two gas fireplaces and a gigantic professional type stove. Currently has a 1" B.I. line. I'm having trouble converting the BTU imput ratings of the appliances to a cubic feet rating for the pipe size. Anybody out there good at this?

  • #2
    Re: Gas pipe sizing

    I'll start by saying that gas lines should be run by a licensed professional.

    Comment


    • #3
      Re: Gas pipe sizing

      You should have a drawing/permit made for something this complex. The code books have charts and a calcluator to help.

      Comment


      • #4
        Re: Gas pipe sizing

        seriously, pick up a copy of the relevant fuel gas code book, add up your BTU load and find that number and the developed length on the chart, it'll pinpoint the size you need.
        No, it's not rocket science, it's plumbing and unlike rocket science it requires a license.

        Comment


        • #5
          Re: Gas pipe sizing

          gas ain't water. water leaks cause mold. gas leaks cause kaboom. breid.......

          Comment


          • #6
            Re: Gas pipe sizing

            this should only be answered by a licensed professional in your area and as far as lam concerned this thread should be closed.
            Last edited by aero1; 09-13-2009, 08:13 AM.

            Comment


            • #7
              Re: Gas pipe sizing

              If you are a gas-fitter then the training for sizing gaslines should have been thouroughly covered in school, and as mentioned the gas code has all relevant tables for sizing any system.
              If you are not a gas-fitter do not attempt to do this yourself.
              Gas is perfectly safe if properly installed by trained qualified persons, and should NEVER be attempted by anyone without proper qualifications and training. The repercusions can not only harm you or your customer, but can take out half a neighborhood!! I have seen this and it is not a pretty sight.

              Comment


              • #8
                Re: Gas pipe sizing

                Everything is measured in CF and distance per UPC. Atleast, here, it's the UPC. Your area might be different.

                If you can't read a code book, then you probably shouldn't be installing gas.

                There is no easy way, there is only the right way.
                Last edited by westcoastplumber; 09-12-2009, 06:47 PM.
                sigpic

                Robert

                Comment


                • #9
                  Re: Gas pipe sizing

                  Round number, a cubic foot of ng is about 1000 BTU. ( It is usually closer to 1100, but can vary with time of year from the supplier, who uses something called a therm multiplier for billing.) But if you use 1 cuft = 1000 BTu it is easy figuring, and gets you in the ballbark.

                  Sounds like you are not familiar with the National Fuel Gas Code and the UPC or IPC, so you may need some outside help on this?

                  Comment


                  • #10
                    Re: Gas pipe sizing

                    Originally posted by lovetheUSA View Post
                    Round number, a cubic foot of ng is about 1000 BTU. ( It is usually closer to 1100, but can vary with time of year from the supplier, who uses something called a therm multiplier for billing.) But if you use 1 cuft = 1000 BTu it is easy figuring, and gets you in the ballbark.

                    Sounds like you are not familiar with the National Fuel Gas Code and the UPC or IPC, so you may need some outside help on this?
                    Wouldn't you know it. A supplier had to spill the beans. Shame on you!!

                    Comment


                    • #11
                      Re: Gas pipe sizing

                      gas is sized by the total demand, total developed length, and acceptable pressure drop.

                      first thing you need to establish is your total demand in btu's. this then gets converted to cubic feet. out here we use 1100 btu's to the cubic foot.

                      you also need to know what sizing tables you use for your location based on delivered pressure and acceptable drop off pressure.

                      out here/ los angeles, we are at 7'' w.c. with a drop of .5 w.c.

                      with these low pressures, our lines are traditionally larger and more conservative than other locations that start with higher pressures and allow a larger drop.

                      total developed length is the distance from the gas meter/ regulator, to the most remote location. with 2 tankless you're already into the 400,000 btu range most likely. the farther the large demand/ tankless are from the meter. the longer the large main piping size will have to be run downstream. keeping the high demand/ tankless closer to the meter, will allow you to use less large diameter piping.

                      hopefully you take all considerations into account and design and install a safe and properly working gas system.

                      remember, not all inspectors know or inspect right from wrong when it comes to sizing. lots just look for a pressure test.

                      i would draw up the system with all the numbers, distances and figures, and run it through your local building departments inspector, plan check.

                      typically the plan checker will verify your numbers and sign off on the design.

                      threaded gas pipe and threaded water pipe is pretty much the same. black iron/ galvanized iron is the difference. it's what's inside that makes a potential leak the difference between a wet wall, ceiling, floor and no walls left standing

                      keep that in mind when working with gas, or hiring the pro of choice.

                      good luck, do your math and drawings and check it with the building department.

                      rick.
                      phoebe it is

                      Comment


                      • #12
                        Re: Gas pipe sizing

                        [QUOTE=PLUMBER RICK;251699]gas is sized by the total demand, total developed length, and acceptable pressure drop.

                        first thing you need to establish is your total demand in btu's. this then gets converted to cubic feet. out here we use 1100 btu's to the cubic foot.

                        you also need to know what sizing tables you use for your location based on delivered pressure and acceptable drop off pressure.

                        out here/ los angeles, we are at 7'' w.c. with a drop of .5 w.c.

                        with these low pressures, our lines are traditionally larger and more conservative than other locations that start with higher pressures and allow a larger drop.

                        total developed length is the distance from the gas meter/ regulator, to the most remote location. with 2 tankless you're already into the 400,000 btu range most likely. the farther the large demand/ tankless are from the meter. the longer the large main piping size will have to be run downstream. keeping the high demand/ tankless closer to the meter, will allow you to use less large diameter piping.

                        hopefully you take all considerations into account and design and install a safe and properly working gas system.

                        remember, not all inspectors know or inspect right from wrong when it comes to sizing. lots just look for a pressure test.

                        i would draw up the system with all the numbers, distances and figures, and run it through your local building departments inspector, plan check.

                        typically the plan checker will verify your numbers and sign off on the design.

                        threaded gas pipe and threaded water pipe is pretty much the same. black iron/ galvanized iron is the difference. it's what's inside that makes a potential leak the difference between a wet wall, ceiling, floor and no walls left standing

                        keep that in mind when working with gas, or hiring the pro of choice.

                        good luck, do your math and drawings and check it with the building department.
                        And if it's a carpenter,elec. plumb. insp. all in one [ common in the rural areas ] He won't have a clue whats He's looking at !
                        I can build anything You want , if you draw a picture of it , on the back of a big enough check .

                        Comment


                        • #13
                          Re: Gas pipe sizing

                          At what point do we say that we don't need to show off our knowledge and let somebody call a plumber?
                          Buy cheap, buy twice.

                          Comment


                          • #14
                            Re: Gas pipe sizing

                            Originally posted by PLUMBER RICK View Post
                            out here we use 1100 btu's to the cubic foot.


                            rick.
                            Rick
                            Though the 2007 CPC still uses 1100btuh=1cfh, many California gas utilities are supplying gas at approx. 1050btuh=1cfh. That being the case, many contractors are using (1000=1) as the conversion formula just to error on the safe side. I guess the surest answer is to contact your local utility, in your case SoCal Gas and in mine PG&E.

                            Comment


                            • #15
                              Re: Gas pipe sizing

                              Originally posted by PLUMBER RICK View Post
                              gas is sized by the total demand, total developed length, and acceptable pressure drop.

                              first thing you need to establish is your total demand in btu's. this then gets converted to cubic feet. out here we use 1100 btu's to the cubic foot.

                              you also need to know what sizing tables you use for your location based on delivered pressure and acceptable drop off pressure.

                              out here/ los angeles, we are at 7'' w.c. with a drop of .5 w.c.

                              with these low pressures, our lines are traditionally larger and more conservative than other locations that start with higher pressures and allow a larger drop.

                              total developed length is the distance from the gas meter/ regulator, to the most remote location. with 2 tankless you're already into the 400,000 btu range most likely. the farther the large demand/ tankless are from the meter. the longer the large main piping size will have to be run downstream. keeping the high demand/ tankless closer to the meter, will allow you to use less large diameter piping.

                              hopefully you take all considerations into account and design and install a safe and properly working gas system.

                              remember, not all inspectors know or inspect right from wrong when it comes to sizing. lots just look for a pressure test.

                              i would draw up the system with all the numbers, distances and figures, and run it through your local building departments inspector, plan check.

                              typically the plan checker will verify your numbers and sign off on the design.

                              threaded gas pipe and threaded water pipe is pretty much the same. black iron/ galvanized iron is the difference. it's what's inside that makes a potential leak the difference between a wet wall, ceiling, floor and no walls left standing

                              keep that in mind when working with gas, or hiring the pro of choice.

                              good luck, do your math and drawings and check it with the building department.

                              rick.
                              Completly irresponsible on your part Rick

                              Comment

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