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Standby Generator Gas Line Sizing

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  • Standby Generator Gas Line Sizing

    OK guys, I am considering getting a 8KW NG powered Generac Standby Generator. I have a 3/4 inch line within 3 feet of where the pipe will go out to feed the generator. My question is will the 3/4 pipe feed both an 80,000 BTU furnace and the gen set at 80 CF per hour?


  • #2
    Re: Standby Generator Gas Line Sizing

    What other gas appliances do you have in your house? What size line is coming in from your gas meter?

    I know in Pa. we can use 12/2 gas which is a higher pressure and there for we don't have to run 1" or 1 1/4" to the furnace/boiler.

    Somewhere I got my gas piping only if I can find the darn thing.


    • #3
      Re: Standby Generator Gas Line Sizing

      That can be calculated but you will need to have the layout of the existing pipe, the kind of pipe (CSST/iron pipe), the length of the sections in the runs, how many fittings and what kind they are and the static input pressure to the system. Once these are known it will be possible to calculate this.

      I'm sure Plumber Rick will give you the answer


      • #4
        Re: Standby Generator Gas Line Sizing

        3" always. go with 3", 3" will handle just about anything you hook to it. Welded pipe would be good also.


        • #5
          Re: Standby Generator Gas Line Sizing

          most likely it will not. but you need to get the total developed length on the pipe run to the meter. basically you need to size the entire system.

          fortunately, this is an emergency standby generator. so the little it will get used, is more of an inconvenience. as long as you're not planning on heating the house when the generator is running, the 80,000 btu heater is almost identical to the 80 cfh you're needing.

          but in reality, need to know your gas pressure and pressure drop along with the total developed length and demand.

          is the pipe black steel or galvanized (inside joke)

          phoebe it is


          • #6
            Re: Standby Generator Gas Line Sizing

            Rick - I did not think he specified that it was iron pipe - it could be CSST or even copper for all we know. But I think we should tell him to use galv - after all here in Cali we call it the miracle pipe, yes .

            Buckwheat - if you can sketch or draw the exact layout I think people can give an accurate answer. But you will also need to know the static pressure (ie no load pressure) at the meter. Do you have a manometer to measure? I believe you are supposed to size for worst case scenarios - ie using everything at full load at any time.


            • #7
              Re: Standby Generator Gas Line Sizing

              Thanks guys, but I had the gas company out and they said it was a no go due to service size. I guess I will just have to get a little better about exercising my Diesel gen set a couple of times a year. As far as the Galv vs black pipe discussion, it is galv up to the meter and black from there on.

              Once again, thanks for the input.