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Natural Gas Pipe Dimensions for Onan JC


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  #1  
Old 11-10-2017, 03:28:51 PM
JT240Z JT240Z is offline
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Default Natural Gas Pipe Dimensions for Onan JC

I have a 15.0JC that I'm going to be plumbing into my NG system. The generator is going to be sitting approximately 20' from my gas meter. I currently have a 1 1/2" outlet from the gas meter. I'm trying to balance cost and needs to come up with a plan to run the gas line. I obviously don't need to run 1 1/2" all the way to the generator. The technical bulletin T-015 specifies 1" line for 15' and 1 1/4" line starting at 25'. The line going into the cutoff switch and demand regulator is only 3/4". I obviously will have to reduce the pipe dimension down to the 3/4" line sometime before that and will probably use 3/4" flex line to do the final connection although 1" line is available if needed. My current plan is to run 1 1/2" line into a tee (to provide access to supply the rest of the house in the future) and then reduce to 1 1/4" line for most of the way to the generator housing. From there I'll reduce down to either 1" or 3/4" pipe and make my entry into the generator shed with that. My question is, does this make sense? The cost and availability of 1 1/4" pipe and fittings are significantly more than either 1" or 3/4" so I really only want to run the larger diameter pipe for as long as I need to. Any suggestions on specing this out? Plan to do the work myself. I've run black iron pipe in the past so that's no issue.

The layout would be something like this:
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Old 11-10-2017, 06:36:44 PM
Jim Marcozzi Jim Marcozzi is offline
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Default Re: NG pipe dimensions for JC

My 12.5 JC was 90' from the meter. I teed into the meter outlet with 1" yellow plastic and went to the JC with it. In the enclosure, I had a shutoff and it went into the demand regulator with 3/4" flexible. Load tested full output.
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Old 11-10-2017, 06:54:01 PM
JT240Z JT240Z is offline
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Default Re: NG pipe dimensions for JC

So are you saying that I'm over thinking this? I thought about just running 1" pipe since the distance was very close, but between the Onan recommended size pipes for 15' and 25'. The problem is that the line is 20' away but will have a couple elbows along the way. I was told to add 5' of pipe length for every 90-degree bend. That would make the calculated distance more like 35'. Was thinking of running only about 10 or so feet of the 1 1/4" pipe in order to get closer to the shed and than go with the 1" pipe from there on. Right now my meter only feeds my furnace and the 1 1/2" pipe tees with a cap on one side and a 3/4" line going to the furnace. A little overkill but I asked for a larger meter so I could add the genset and future gas appliances. A gas stove and water heater would go a long way in a power outage.
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Old 11-10-2017, 07:04:01 PM
Jim Marcozzi Jim Marcozzi is offline
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Default Re: NG pipe dimensions for JC

I prefer a larger pipe, when possible. It acts slightly as a reservoir and dampens any pulsations.

You also need to calculate the gas usage for water heater, cooking, heating, etc then add in the generator's consumption. All added together, your meter, regulator (if used) and delivery service (street lateral pipe) needs to be able to handle the volume of all units running togther.

If not, the gas co will be glad to install a larger meter in most cases.
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Old 11-10-2017, 07:33:58 PM
Max Thompson Max Thompson is offline
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Default Re: NG pipe dimensions for JC

Per. the Uniform Plumbing code 1” pipe will deliver 259 CFH up to 60’ @ 0.5” water column.

I think it is common practice to count each 90 as 10'. It looks like if you are going to do a "text book" installation, you will be real close with 1" pipe all the way.

If you have 7" WC pressure at the meter or more, I would run 1" and not worry about it. Just keep the elbows to a minimum.
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Old 11-10-2017, 07:48:49 PM
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Default Re: NG pipe dimensions for JC

/\ +1 with Jim. I also agree with JT240Z about elbows causing some restrictions. I believe in having a little more than finding out I didn't go big enough. "Do the job right the FIRST time then you will never have to go back and fix it right the NEXT time." With extra capacity, you could add in another outdoor appliance such as a gas BBQ... And then cook ALL of US here on the site some BBQ RIBS!!!
My 7.5JB is right at my gas meter but I have a 1.25" ID rubber gas flex hose of 12 ft. I want to move my JB to the other side of my home and into my carport where I park my Pickup. For the 50 ft I need to get the Nat. gas there, the T-015 calls for 3/4 inch but jumps to 1.25" at 75 ft.
I am going 1.25" the whole length because I eventually want to tie into the line at about 1/2 way to put in a Nat Gas BBQ and maybe an outside WOK burner to be able to stir fry outside so I don't stink up the house. NO I an not going to "WOK the Dog!"
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Old 11-10-2017, 07:59:36 PM
I like oldstuff I like oldstuff is offline
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Default Re: NG pipe dimensions for JC

JT you're golden with your approach. Run with it.
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Old 11-10-2017, 10:53:55 PM
len k len k is offline
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Default Re: NG pipe dimensions for JC

I like to plan ahead, on other things been bite by designing to current needs, then later wanting to upgrade.

Like idea of larger than required line if you can afford it. Then will be set for possible larger gen in future. Most of the back breaking work is in digging the trench. I'ld even add extra empty plastic conduit for future control wires , ect.

I'ld even put the power wires in plastic conduit, so can easily replace them if they fail in 30 years or so. Read of underground 120V utility feed to house fail, was ~ 150 ft uphill.

Last edited by len k; 11-10-2017 at 11:07:02 PM.
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Old 11-11-2017, 09:07:18 AM
scoops scoops is offline
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Default Re: NG pipe dimensions for JC

Quote:
Originally Posted by Jim Marcozzi View Post
My 12.5 JC was 90' from the meter. I teed into the meter outlet with 1" yellow plastic and went to the JC with it. In the enclosure, I had a shutoff and it went into the demand regulator with 3/4" flexible. Load tested full output.
I never thought about this Jim.
my natural gas meter is also about 90 ft from my house.
my shed where genny will be is 1/2 way between meter and house.
are you saying i can have a plumber tee off the meter?
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Old 11-11-2017, 10:01:11 AM
Gunny Gunny is offline
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Default Re: Natural Gas Pipe Dimensions for Onan JC

In my opinion, for what that's worth, you'll be OK. If you can find them, use long sweep 90's, less restriction. Or even better, get some of that 1" plastic the gas company uses with no elbows.
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