# natural gas sizing help...



## younger-plumber (Sep 12, 2008)

I have a customer that currently has lp and will be changing to natural gas.I am making sure the current size pipe is sufficient when changed to n/g.I am running 80 foot on 1/2 soft copper to the 100.000 btu a/c / heater.according to nc code this should be fine , any advice/constructive criticisms about using the same old copper( 8 years old) Inspector approved it to be re-used if sized appropriately.


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## SlickRick (Sep 3, 2009)

We use the National Fuel Gas Code here.


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## younger-plumber (Sep 12, 2008)

thanks?


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## SlickRick (Sep 3, 2009)

younger-plumber said:


> thanks?


Why the ? LP carries more btu's than NG. National gas code would only allow a few feet of 1/2" at 100,000 btu. But you need to check the developed length to the most remote appliance and btu loads starting at the meter and working to the last appliance.


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## dclarke (Dec 22, 2012)

How many gas appliances are there ? I would most likely run 1" but that depends on what exactly you have. Need more Info


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## SlickRick (Sep 3, 2009)

Sorry, link did not copy.


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## Tommy plumber (Feb 19, 2010)

Just shooting from the hip and without looking it up in the fuel gas code book {it's 11:00 PM here and I'm tired} I will hazard a guess that 1/2" for 80' at 100,000 BTU is probably undersized. But don't quote me, you'll have to look at the charts in the gas code book.

It may have been ok for LP, but it will probably be undersized for natural gas.


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## BC73RS (Jan 25, 2014)

In my gas code it's good too as long as a 2 psi system is used.


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## plbgbiz (Aug 27, 2010)

Not sure what your pressure drop is but at 100,000btu, the 1/2" was undersized on propane. 

If I am reading the charts correctly, you could getaway with 3/4" steel on NG if the btu's are 117K or less. To keep copper, it looks like you would have to run 1". Either way, 1/2" copper is a no-go.


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## SlickRick (Sep 3, 2009)

Remember that the length in ft. is from the meter to the furthest appliance, and stay on that line to calculate loads and sizes. Some get confused go from line to line in footage, that's not the way it works.


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## younger-plumber (Sep 12, 2008)

according to my code book I need to find out what the pressure drop is...what is the formula for this? I cannot find a reliable source to confirm


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## plbgbiz (Aug 27, 2010)

Your gas provider can tell you, or the AHJ.


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## BC73RS (Jan 25, 2014)

To avoid any confusion here is my chart from the Canadian Gas Ass.
Sorry for the lousy pic. but it's all I can do for now...off to work...


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## younger-plumber (Sep 12, 2008)

Called the gas company. Gonna be a 2 pound system and they said average is 1 pound pressure drop. If that's the case then the 1/2 line will be plenty according to the code book. He did say each unit will now need a regulator to reduce the pressure. Any insight?


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## plbgbiz (Aug 27, 2010)

younger-plumber said:


> Called the gas company. Gonna be a 2 pound system and they said average is 1 pound pressure drop. If that's the case then the 1/2 line will be plenty according to the code book. He did say each unit will now need a regulator to reduce the pressure. Any insight?


2psi regulators are pretty common. Most supply houses have been carrying them since CSST hit the street.


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## evan (Dec 10, 2010)

how many appliances are there? are you sure you want to put a regulator at each one?
If its just a furnace and a water heater thats one thing. If its a furnace, WH, range, dryer, fireplace .... it might be easier to re-run one line and have it be a 1/2 pound system. Just have to check the rest of the lines arent undersized too


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## plumbdik (Aug 6, 2013)

Make sure the 2 psi regulator is "heavier duty" like a Pietro type or it can lock up pretty easy. You can adjust the spring to calibrate proper in of W.C. for unit/appliances.


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## Plumb26 (May 18, 2013)

younger-plumber said:


> Called the gas company. Gonna be a 2 pound system and they said average is 1 pound pressure drop. If that's the case then the 1/2 line will be plenty according to the code book. He did say each unit will now need a regulator to reduce the pressure. Any insight?


Here in NC, and I believe you're from here, you have to put test Ports before and after the regulator and both need to be 10 times the pipe diameter away from the vent on the regulator. You have to hard pipe all floor and foundation penetrations and they should be sleeved as well. Don't forget to purge the crap out of the old line if you reuse it and make sure all of the appliance conversions get done before putting any fire to anything. Have fun..... Gas is easy, just be careful.


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## Tommy plumber (Feb 19, 2010)

Why does the fuel gas code book state in the sizing tables '_cubic feet of gas per __hour'_ for natural gas yet '_thousands of BTU's per hour_' for propane? Is it because natural gas is a utility measured by the gas meter in cubic feet?


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## Plumb26 (May 18, 2013)

Never made sense to me either. It's really the same number anyway.


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## BC73RS (Jan 25, 2014)

We debated that in tech school way back (BCIT), some gas companies provide higher calorific valued natural gas than others. Albeit 1000 btu's per cu.ft. is the norm, I've heard in BC you can get as high as 1050 btu's.


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