Natural gas line sizing with generator addition

I am looking at installing a standby generator that uses ~320cfh of natural gas. My utility company said I will have to have a bigger meter installed as I already have ~250cfh of potential usage with everything else on.

It's a little unclear to me as to whether I'll need a new pipe run from the curb stop to the house. It measures about 1.6 inches OD, with the meter about 50 feet from the road, and has 1/4 psi inlet pressure. Looks to be made of HDPE or something similar. I see some conflicting information online regarding this but I think I'm in the clear. Thoughts? Are there standards for this type of pipe to let me know what the ID likely is?

• I'm curious, is the pressure on the utility line from the street 1/4 pound or do the have a regulator at the curb? I'm in Toronto and our utility runs high pressure (10lbs or so) right up to the meter at the house and regulates it down there. That way they can deliver cfh in the thousands if necessary on a 3/4" line. Where do you live? Mar 22, 2019 at 11:40
• Hi - the pressure is coming in at 1/4 from the utility and there's no regulator at the meter. I'm in the states.
– Ryan
Apr 2, 2019 at 12:49

Natural gas is conveniently 1000 btus per hour per cubic foot per hour so 320 cfh =320 mbtu/h. Your gas line with a 1.6" outside diameter is an 1-1/4" I.D. pipe. At 50' it will be capable of delivering 561 mbtu/h or 561cf/h

Here's a reference Perfection pipe calculator

This chart is rated with a 6" water column and your 1/4 psi is 7" water column so 561 is slightly underrated from what you'll actually be getting.

Edit

It seems the chart you're looking at is using a derated figure for natural gas' calorific value.

Most charts I've ever seen use the calorific value from the google sherch pictured above.

I can only guess that that from your link they are going with the lowest quality refined gas available. I'm going to read the whole link later because I'm curious. It may be for "wet gas" but they are got rid of that stuff in the 70's through better refining processes.

• This seems to be different than: codes.iccsafe.org/content/IFGC2018/… - table 402.4(21) is there a reason that it significantly varies?That seems to be the table that best reflects my setup, including specific gravity, pipe material, and pressure drop.
– Ryan
Mar 23, 2019 at 5:57