# Nat gas line sizing Q.



## RASelkirk (Sep 18, 2020)

Hi All,

Need some clarification on line sizing. This direct quote from Champion Power Equipment's install PDF shows conflicting info:



> Gas supply and pipe MUST be sized at 100%
> load BTU rating. Understand that as a specific fuel supply line
> pipe diameter is extended in length, its ability to carry the volume
> of gas is diminished in direct proportion.
> ...


First recommendation is to add 2.5' per all relevant fittings, then it shows an exception of 8' per 90°. So which should it be? I'll likely end up with ~ 40' of pipe, one "tee", and three 90°s. Haven't pegged an exact size yet, prolly looking at 260 cf/hr max. I'm hoping to avoid going larger than 1" steel...

Thanks!

Russ


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## Jackruf (Nov 4, 2012)

The US Carb website provides some good information on NG piping size


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## drmerdp (Apr 10, 2018)

What model generator are we talking about?


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## RASelkirk (Sep 18, 2020)

Jackruf said:


> The US Carb website provides some good information on NG piping size


Ugh, shows 1 1/4". Link for others, thanks!



drmerdp said:


> What model generator are we talking about?


I don't have a particular one in mind yet, doing a (mental) site-prep right now. Will be looking at 12 - 20kW eventually. Fuel usage isn't different enough over that range to matter in the calc's...

Russ


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## drmerdp (Apr 10, 2018)

Gotcha, your looking at 1 1/4 minimum. Unless you go with a 2 psig setup... You can get away with A Much smaller pipe like 1/2 or 3/4“.


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## RASelkirk (Sep 18, 2020)

Gas company has already stated I'll need a larger meter, I'll have to ask about that. I _think_ the header here runs 150 PSI, so maybe they could just add a second meter with the 2 PSI setup. I'm assuming this would require a step-down to 10" at the generator site? My main into the house is 1", the tan line is a 12 foot run to the cooktop from our 2017 remodel as the builder didn't want to rip out the inside walls...

Russ


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## iowagold (Jan 22, 2020)

yea they change out the main high pressure regulator to a LARGE flow output..
go the super large 3 inch commercial service meter.
then do a T with dual shut off valves after the meter.
neck down to the lines.
that makes it nice if you have to work on just one branch of the lines.
i agree with the large line for the gen set..
go with 50% larger than they say with adding up the subtraction for the connectors as well as any 45's and 90 deg.
always go the next size larger when it is close on the rating.

yea it would be cool to set 2 meters... it depends on the gas co rules..
they have a silly rule here for only one meter per house...

but you can get around that with the apartment rules.
or the work shop rules.
at least in my area.


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## iowagold (Jan 22, 2020)

RASelkirk said:


> Hi All,
> 
> Need some clarification on line sizing. This direct quote from Champion Power Equipment's install PDF shows conflicting info:
> 
> ...


so exactly how many btu do you need on your gen set???
of is it a gx390?
and how many btu is the rest of the house?

I have found that the one inch lines here work great on a gx 390 with a honda eu7000is ng kit.

one inch line is rated at 1m btu.
and yea you have to subtract the fittings etc.
here is the kicker
if you do a T like in your photo and keep the line short or under 20 feet.
then yea the meter you have will work if you have a small furnace under 150k btu.

you can run larger pipe on that super long run with the current meter and save some flow resistance..

but yes you are better off with high pressure close to the generator then dual regulators at the gen set.

did you find out if they will let you have a dual meter setup on the same gas account?

you might have to do the second meter like it is for a garage or an apartment..
watch city code on that as they might flag you for an apartment..
some times the property taxes are more for a commercial or biz connection thing..
just saying something now as it is a question...
it can be a can of worms!!
been there done that.

most of the ng and lp charts are good over kill if they system is planned right.

a flow meter as well as a pressure meter will show any issues.


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## RASelkirk (Sep 18, 2020)

This is my load, gen is a worse-case guess figured for 20kW (lpg)/18kW (nat):

______________________BTU load________CFH
Cooktop:______________60,000_______60____60
Water Heater:_________40,000_______40____40
Furnace:_______________74,000_______74____74
Dryer: _________________22,000_______22 ___22
Generator (half/full)________________190__300

Total:_______________________________386___496

All the existing stuff runs off a 3/4" header inside the house (except the cooktop), the gen will need to be on a separate tee at the meter. Forgot my gas log fire, it obviously wouldn't be a factor during hurricane season.

It's a shame it took me 20 minutes to "format" my table, why don't forums allow for the tab character? <LOL>

Russ


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## iowagold (Jan 22, 2020)

i see it as too small on the house feed.
at least at any real run..
how many feet are each branch and the main run?

mine was 3/4 for the furnace and stove and was pushing it..
that was at 30 feet.
you could see flame drop off on the stove.
the new system has better runs and is perfect.
1 inch feeding the house now.
stove, water heater, furnace.
then a dedicated 1 inch for the gen setup.


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## drmerdp (Apr 10, 2018)

Diameter of pipe is one thing, the length is the other. 3/4“ can be enough volume, but only if the total length is pretty short.

I certainly prefer an oversized system instead of only adequate.


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## RASelkirk (Sep 18, 2020)

House piping is not an issue, house was built in 1974, we've owned it since 1987 and never had a problem with any gas appliances (other than wearing out and replacing with more efficient ones). We are located in SETX where we do not have the heating load you "yanks" have. Our gas bills in summer are low $20s, winter months < $100...

Russ


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## iowagold (Jan 22, 2020)

did the cook top numbers include the oven?
some of the modern units are 150k btu total max with all the burners and pre heat on the oven...
depending if your unit has the 20k each turbo burners.

the like 3/4 id just for the stove on some of them...

how long are the runs?
and how many 90 deg fittings and or T's?

one inch is supposed to be 1m btu at the meter for natural gas.
at least at my location.
that is before any length and fittings.


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## RASelkirk (Sep 18, 2020)

Oven is electric. I'm 67 and not particularly inclined to crawl thru my attic measuring gas lines that have been perfectly adequate for the last 45 years. The gen would be on a separate run from the meter, so (new meter aside) inner-house line sizes are all moot.

Russ


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## iowagold (Jan 22, 2020)

just have the gas utility set a second meter at the large generator location.
that will get you high pressure to the location so the lines from the home owner side will be short.
10 to 20 bucks a month for min service charge.
and make sure the meter will handle up to 2 inch line.
that will get you a large service for a good generator.

I like generator pipe line runs less than 40 feet.
20 feet nom.
that will get the meter and regulator far enough away for the inspection pass.


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