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Old 11-30-2016, 09:11 AM   #1
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Natural gas piping question


I am new here so please bear with me if I put this in the incorrect location.

I am going to be adding a gas range to my house very soon and I want to be sure I have the correct piping in my home. I have added a rough diagram of what my current system looks like along with an actual picture of it. Also a table showing the BTU demands, piping length and diameter. Please let me know what size piping I should use for the stove and if anything else should need to be changed.

Gas meter: AC-250 (250 CFM)
2 PSI natural gas system
Farmington, MN

Branch BTU Length Diameter
Main 00000 32' 1/2''
dryer 22000 15' 1/2''
furnace 80000 2' 1/2''
fire place 40000 42' 1/2''
Tankless w/h 200000 15' 3/4''
Range 84500 35' ??
TOTAL BTU 426500

Last edited by iaminsider; 11-30-2016 at 09:16 AM.
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Old 11-30-2016, 09:15 AM   #2
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Re: Natural gas piping question




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Old 11-30-2016, 12:39 PM   #3
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Re: Natural gas piping question


Short answer: at least 3/4". But do some google searching, there are tons of sizing charts out there. You already have the load, size, and lengths, so it shouldn't be too hard to figure out.
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Old 11-30-2016, 12:47 PM   #4
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Re: Natural gas piping question


With the 2 psi system that my home has, it sounds like 1/2'' might be sufficient but I think I will just run 3/4''.

How about my meter? My total demand will be 427k btu but the meter is rated as 250cfm. Actually my current demand is 342k btu running through the 250cfm meter. Does the fact that my house has 2 PSI coming from the meter change that calculation?

Am I going to need to worry about the fact that only 1/2'' copper is running from the meter to the distribution in the basement? It seems like running at 2 psi is allowing the 1/2'' feed from the meter be sufficient currently but will that still be the case adding in another 84500 btu draw with the gas range?
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Old 12-01-2016, 11:10 PM   #5
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Re: Natural gas piping question


Quote:
Originally Posted by iaminsider View Post
I am new here so please bear with me if I put this in the incorrect location.

I am going to be adding a gas range to my house very soon and I want to be sure I have the correct piping in my home. I have added a rough diagram of what my current system looks like along with an actual picture of it. Also a table showing the BTU demands, piping length and diameter. Please let me know what size piping I should use for the stove and if anything else should need to be changed.

Gas meter: AC-250 (250 CFM)
2 PSI natural gas system
Farmington, MN

BranchBTULengthDiameter
Main 00000 32'1/2''
dryer 2200015'1/2''
furnace 800002'1/2''
fire place 4000042'1/2''
Tankless w/h 20000015'3/4''
Range 8450035'??
TOTAL BTU426500
Sorry all I have is my own code book, which is the CSA B149. Although you're in a different jurisdiction, the math will be similar.

At 30ft, 2psig, 1.5psi max drop, 1/2" OD copper tubing is only rated for 312,000 btu. That main line is undersized without the range. 5/8" allows up to 544,000 at 40ft at the same pressures. (636k at 30ft)

You haven't mentioned what you've set your regulators to. This is important. However, at 7-14" WC working pressure, 1/2" black iron will do at 40ft. (107k btu at 40ft) However, if you run copper tubing, it'll have to be 3/4" OD. (121k btu at 40ft)

PS. Those regs are supposed to be exterior vented here. That means running pipe from the vent straight outside. A relief device is also required down steam of both regs. (unless they are combo devices but they don't look like it.) Your rules could be different though.



Cheers!

Last edited by supers05; 12-01-2016 at 11:19 PM.
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Old 12-02-2016, 01:10 PM   #6
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Re: Natural gas piping question


Quote:
Originally Posted by iaminsider View Post
With the 2 psi system that my home has, it sounds like 1/2'' might be sufficient but I think I will just run 3/4''.

How about my meter? My total demand will be 427k btu but the meter is rated as 250cfm. Actually my current demand is 342k btu running through the 250cfm meter. Does the fact that my house has 2 PSI coming from the meter change that calculation?

Am I going to need to worry about the fact that only 1/2'' copper is running from the meter to the distribution in the basement? It seems like running at 2 psi is allowing the 1/2'' feed from the meter be sufficient currently but will that still be the case adding in another 84500 btu draw with the gas range?
Your home is not 2 psi. You can get away with 1/2" feeding your home because up until the regulator, it's 2 psi. After the regulator it's probably less than 14"w.c. (1psi = 27.7"w.c.), like super05 mentioned.

You are right that you might be OK with 1/2", but you are cutting it close, and since it's not installed yet, 3/4" is the safe bet and will cost little more.

You have probably been alright with a 250cfm meter because not all of your appliances are maxed out at the same time. And unless you are planning on taking a full blast hot shower while have a fire in the fireplace, drying a load of laundry, boiling a pot of water, and running the furnace at the same time, you should generally be OK.
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Old 12-02-2016, 06:56 PM   #7
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Re: Natural gas piping question


Thank you for all of the help folks.

I apologize for not being clear. I was aware that I was running 2 PSI from the meter to the regs and less after. The regs are 7-11 WC.

The gas company is going to be swapping me to a 425cfm meter in the next week or so. That part has worked it self out.

Now.... Do you folks think that 1/2'' copper from the meter into the house at 2 PSI carries enough gas for 427k BTU?

P.S. both of the regs have a tag on them stating that they are ventless regs from Maxitrol. The house passed inspection when I bought it so I don't have much concern that we are not set up correctly.... should I?
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Old 12-02-2016, 08:08 PM   #8
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Re: Natural gas piping question


The current meter was probably fine, but upgrading never hurts. (the rating is usually for less the 7" WC. At 7-14"wc you have plenty of capacity to spare. At wet psi, you don't have much to worry about.) At any rate, I always leave that up to the utility. It's their responsibility.

You're interior regs have vent limitors in them. If there is ever a rupture, they only leak a small amount by design. If it passed inspection, then don't worry a second more. Rules change from place to place. Maxitrol has a list of indoor vent limiting devices on their website if you want to double check. (as compared to the outdoor versions)

Here, the 1/2" incoming line wouldn't pass inspection. It's too small.

Cheers!
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Old 12-03-2016, 10:30 PM   #9
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Re: Natural gas piping question


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Originally Posted by supers05 View Post
You're interior regs have vent limitors in them. If there is ever a rupture, they only leak a small amount by design. If it passed inspection, then don't worry a second more.
Sorry to hijack the thread but I have never seen a regulator on any natural gas system in any house I have owned (beyond the one with the meter). Is this a jurisdictional thing? Just interested.
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Old 12-03-2016, 10:40 PM   #10
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Re: Natural gas piping question


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Originally Posted by lenaitch View Post
Sorry to hijack the thread but I have never seen a regulator on any natural gas system in any house I have owned (beyond the one with the meter). Is this a jurisdictional thing? Just interested.
Don't think so... just very rarely needed. They also aren't cheap, so if you don't need to use them, why add them. When the piping gets longer, it starts to make more sense.

Cheers!

Last edited by supers05; 12-03-2016 at 10:44 PM.
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