need help on calculating pipe size on natural gas lines...

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Old 12-18-12, 07:56 AM
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need help on calculating pipe size on natural gas lines...

I am running new gas lines from my meter to my dryer (30,000 BTU) and my range (165,000 BTU).

I am finding conflicting information. One chart says devide BTUs by 1,100 to calculate CuFt/hr another says 1,000.

Second, I read in one resource that I should be adding 10' to the distance of the run for each 90 degree elbow and 5ft for each 45 on the system? MOST resources dont mention this addition?

At the absolute minimum, logistics require 5x 90 degree elbows. The most convenient configuration would be 8. Should I be adding additional length in my calculations to account for resistance at an elbow?
 
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Old 12-18-12, 08:16 AM
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Are you running right from the meter, or tapping in somewhere on the existing line?

How far is the distance of the to the farthest appliance? That total distance including all turns and such?

Once you know that you work of the pipe chart/btu to determine the size pipe required.
 
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Old 12-18-12, 09:12 AM
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HI lawrosa,
Thank you for helping,

If you look at the original post, it says I am running new lines from meter. The house was built in 1906 and the old lines are leaking and there are gas nipples in the walls and floors for old gas lights. I would feel safer just re-piping to the only two gas appliances in the house, the dryer and the stove.

Total distance will be determined by layout, which will be determined by weather or not I have to add 10ft of length to account for resistance of 90 degree elbows. Its a 5,000 sq ft L shaped home with a foundation and first floor made of 22" thick granite block, with finished basement. Of course the meter is on the North wall of the west wing and the stove is on the south wall of the kitchen in the south wing, and that is the only section of the house built over non-excavated space.

My question is, when calculating the length of the run, should I be adding a multiple to the length calculation to account for resistance at 90 degree elbows.
 
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Old 12-18-12, 09:17 AM
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There are also 3 substantial granite chineys that go all the way down to the basement floor making a straight run impossible. I want to know about adding length to the calculation for elbows to determine weather I should take a shorter route with more turns or a longer route with fewer elbows...
 
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Old 12-18-12, 09:29 AM
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Minimum length with multiple elbows is ~40ft. Length with fewest elbows is about 65ft. Also, there are steel I beams spanning the ceiling, different heights in different locations, and again, it is a finished basement.
 
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Old 12-18-12, 09:34 AM
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My question is, when calculating the length of the run, should I be adding a multiple to the length calculation to account for resistance at 90 degree elbows.
You do not account for elbows. You need the total developed length of the farthest appliance.

I want to know about adding length to the calculation for elbows to determine weather I should take a shorter route with more turns or a longer route with fewer elbows...


Whatever way you chose, we need the total distance of develped pipe to the farthest appliance.

Example:

From the meter you may go 20ft straight in, make a right 5 ft, then up 2ft, then straight another 30 ft to appliance...

Total 57 ft.

Thats the first step. Once you find that # you look on the gas chart and find that footage column. Then you find your total btu ( 195k). Then to the left it will tell you what pipe size is needed coming off the meter into the home.

From there, after the first appliance usually, you can break down to smaller pipe from there.





 
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Old 12-18-12, 09:38 AM
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According to the chart here:
http://www2.iccsafe.org/states/orego...s%20Piping.pdf

I THINK i should be adding 2.06ft of length to my calculation for each 90 degree elbow in 3/4" black pipe, but I dont know if I am interpreting the chart correctly.
 
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Old 12-18-12, 09:44 AM
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Something like this .

Name:  gas 1.jpg
Views: 10668
Size:  14.7 KB
 
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Old 12-18-12, 09:55 AM
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You would go buy this chart here.

TABLE 402.4(2) SCHEDULE 40 METALLIC PIPE

Chapter 4 - Gas Piping Installations

The National gas code is easier to follow. Look in my sticky for the codes. To view that one you need to register free.
 
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Old 12-18-12, 11:27 AM
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Thanks, why would I use the 0.5 pressure drop chart instead of the 0.3 or 1.0 chart?
 
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Old 12-18-12, 12:18 PM
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Well I belive thats what typical residential gas meters are. That is the preferred chart from the gas company here in NJ anyhow.

Read your gas meter and see what the Diff is. Call your local autority to confirm what their preferred chart is.
 
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