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Gas line from meter

cartommycartommy Posts: 6Member
Hello I need to know if I hook 1-1/4 pipe NG into the 3/4 tee off the meter and run it 10’ and then 3/4” the rest of approx 60’ to 22kw generator will be adequate? And leave the other 3/4 pipe untouched to my stove and furnace. Dryer and water heater is electric.

Comments

  • STEVEusaPASTEVEusaPA Posts: 3,491Member
    edited July 2018
    Nope.

    The 11/4 will help with your volume, but not necessarily your pressure.
    You need a licensed plumber to do the work, and you need to find out what kind of volume and pressure are needed at the gen, and what you need total.
    Then you probably need the meter/regulator upped. However, once that is upped, you better make sure it doesn't exceed the pressure maximums for your range and furnace, or you'll have a big (BOOM!) problem.
    Then after the licensed plumber hooks everything up, someone (qualified generator person) should come over and do a load bank test, checking the gas pressure with a manometer.
    And if you're running the gas underground, specific code must be followed. In our area you need to run tracer wire, exposed and properly terminated at both ends so the gas line can be located if someone needed to dig.
    Edit: Forgot to mention, make sure your gas co. can supply that amount of gas to your home, especially during peak demand. If they can't, you'll have to switch it to propane and get a big enough tank to get you enough run time for refill in the event of an emergency (4 days).
    steve
  • ZmanZman Posts: 5,334Member
    Your generator will need more than 300,000 btus. Download a gas chart and you will see that you will need a minimum of 1 1/4" all the way to the generator. You will also need to check the meter sizing and evaluate additional losses if you are restricted at the meter by smaller piping.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • EBEBRATT-EdEBEBRATT-Ed Posts: 6,115Member
    @cartommy

    Step 1 is to call your gas utility. They will have the information about your existing load. You will need to provide them with the gas requirements of your generator both pressure required and gas volume (btus or cubic feet required).

    They will check your gas service and see if they can provide the required flow and pressure. Chances are they will install a new gas meter.

    If they can provide the required gas I recommend you hire a licensed plumber or gas fitter to pipe the gas line. A separate gas line from the meter to the generator is best. The gas utilities work stops at plumber taker from their (in most locations)
  • cartommycartommy Posts: 6Member
    I was told by the installer that the meter is big enough but that my pipe coming in will need to be 1-1/4” pipe to first drop. Then 1” to next drop and 3/4 to last as well he said what each drop needed to be for the appliance based on the chart. I was confused as to where from the meter you would start the run when it is being fed with 3/4”?
    Thanks
  • Jamie HallJamie Hall Posts: 11,460Member
    The meter is being fed from the street with 3/4 inch? That's almost certainly not going to work, unless the pressure reduction is at the meter. If the meter is big enough, and the street feed is big enough, the inch and a quarter has to start right at the meter.
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • ZmanZman Posts: 5,334Member
    I think you should draw out your system including pipe sizes, lengths, and ratings of appliances. A picture of the nameplate on the meter would also help.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • LeonardLeonard Posts: 840Member
    edited July 2018
    22kw is a big gen for a house. 15kw Onan JC gens wants 255K btu/hr at full load , so estimating your 22kw will want ~374K btu/hr at full load (read your gen manual for what yours wants). That's ~ 3-4 X a typical house heating load!!

    Typically will require a meter change, or at least an upping of safty flow orfice size in the meter.

    3/4 inch street to meter would likely only work IF gas co runs their street mains at higher than standard building pressure, but some street mains are only at house pressure ( ~ 6 inch WC). You need to talk with your gas co. Will need to add up all your gas loads that will be on at same time. If you want to try to use existing house pipes need to make a drawing of lengths and diameters of existing pipe to calculate if they need to upsized.

    Following maybe helpfull ..... Onan generator manual # T-015 (Onan gaseous fuels manual). It specs out pipe dia required for various pipe lengths and gen demands. It's end of list in below link. Compare your 22kw gen with similar kw sized Onan one, as an estimate.
    http://www.twinslan.net/~n0nas/manuals/onan/
    .
  • cartommycartommy Posts: 6Member
    I do have the gas company engineer coming out to size up the meter and then a plumber from my heating company to install piping. I did research how to size up piping for the the inlet of branch and to each drop of branch and what drop should be based on the international gas code chart. I believe the pressure coming from the street to the meter is probably sufficient because I had a 18kw installed in my previous residence and had to upgrade the meter there as well no other changes at that time.
    Thank you all for your input it has been informative. I have HVAC training and experience but never got into the gas line plumbing and calculating side. Time to go back to school lol thanks again to all.
  • LeonardLeonard Posts: 840Member
    edited July 2018
    Pipe sizing........Basically gas flowing thru a pipe has friction with pipe walls that makes a pressure drop. For a given length and flow rate larger dia pipes have less pressure drop.

    Several ways to estimate total piping pressure drop. But fundamentally one accurate way is to add up all the pressure drops of each length of pipe, and fittings ( elbow, tee, valve, strainer ect). And make sure the total pressure drop is not excessive, need a min pressure at the loads ( appliances/gen). Need to know worst case flow in each length. Fittings are typically handled as being equivalent to an extra x feet of pipe.

    There are likely precalculated charts of pressure drop for a given length of pipe and flow rate ( btu/hr in that length), to make this relatively easy to add up.

    Not really recommended (because of reg failure risk) but sometimes can run the building system at 2 psi to avoid having to retro-fit larger pipe diameter (gens require a lot of fuel) . Gas co has to be able to supply that 2 psi. Need pressure regulators at all your loads to bring that back down to standard gas pressure ( ~ 6inch WC). Check if local code allows it.
  • cartommycartommy Posts: 6Member
    Thanks. I am having the meter upgraded and the gas company engineer said that I have 7”wc coming into my house as that is all that is allowed and so I still believe that 1-1/4 pipe is needed for my branch as the last drop is my generator at 310k btu at max load which will never happen and 2 drops prior to that is 40k btu stove/oven and the 2nd drop is 75k btu max is my furnace. I believe my drops to furnace and stove is good at 1/2” and continue 1-1/4” to gen. Thoughts?
  • cartommycartommy Posts: 6Member
    It’s a 70’ branch I might add from meter it is 27’ to first drop oven 60’ to 2nd drop furnace and 68’ to gen drop.
  • Jamie HallJamie Hall Posts: 11,460Member
    max. load will never happen? Hate to tell you this -- but it happens every time it starts as it comes up to running speed...
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • cartommycartommy Posts: 6Member
    Gtk thanks
  • LeonardLeonard Posts: 840Member
    edited July 2018
    Max load ......Agree with Jamie.

    More importantly Gen will be at WOT ( full gas demand) every time a large load is suddenly dropped on gen ( ei central AC unit starts). Under size gas line and engine may choke/sputter/strain on central AC starting. Fuel starvation.

    Motor starting currents typically are 4-6 X running amps. Such a high load that sometimes need a soft-starter for AC motor just to allow gen to start the AC. So I wouldn't under size the fuel line, or gen will behave as if it were a smaller kw rating

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