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Old 01-30-2012, 08:52 AM   #1
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Propane pipe size


Just wanted someone to double check my plan to make sure it sounds right.

We've got 3 major devices, a furnace 70k btu input, a water heater, 36k btu input, and a range, 80k btu input (max).

I'm thinking 1" black sch 40 pipe enter the house from the provider. From there we run into some T's. (see picture). Each run will be 3/4" pipe. The T'1s be 1" and reduce down for each run. Picture is ugly, but you should get the idea of my intended layout. Permits are in place, and gas (propane) company is coming out tomorrow to tell me where they are placing the tanks. Based roughly on where I think they will go, this is kind of how I intend to lay out my pipes.

The circled area is the arrangement if t's with the leg. I figured the first T can have a reducing elbow on the top into 3/4" to feed the furnace.

Bottom T will provide the leg, and go out with a 1" nipple into another T. That T will go left reduced 3/4" and feed the water heater, and going out forward will feet the range, again reduced to 3/4".

I can probably do this all with 3/4" I think, unless I fudged my calculations but if there is a pro on the forum that wouldn't mind giving me a hint or two that would be appreciated.


-- Joe
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Propane pipe size-gas_routing.jpg  


Last edited by anesthes; 01-30-2012 at 11:21 AM.
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Old 01-30-2012, 09:07 AM   #2
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Propane pipe size


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Originally Posted by anesthes View Post
We've got 3 major devices, a furnace 70k btu input, a water heater, 36k btu input, and a range, (110,000) btu input (max) ... I'm thinking 1" black sch 40 pipe...
With natural gas at 3.5-5" WC that 1" pipe w/should be adequate.
What does your propane supplier recommend and/or your county require?


Last edited by TarheelTerp; 01-30-2012 at 09:09 AM.
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Old 01-30-2012, 11:16 AM   #3
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Propane pipe size


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Originally Posted by TarheelTerp View Post
With natural gas at 3.5-5" WC that 1" pipe w/should be adequate.
What does your propane supplier recommend and/or your county require?
The inspector who gave me the permit told me to size it based on the NFGC, which is what I did. He said to use black pipe, since a gas fitters license is required to use copper tube, or csst (for the fittings I guess). That is fine with me.

The supplier I'm meeting with tomorrow, but I'm not sure how much insight they have into the dwelling itself. They might just want the total use calc for the regulator sizing.

-- Joe
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Old 01-30-2012, 12:17 PM   #4
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Propane pipe size


Did you size all of the runs based on the longest measured run?
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Old 01-30-2012, 12:31 PM   #5
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Propane pipe size


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Originally Posted by hvac benny View Post
Did you size all of the runs based on the longest measured run?
Yeah, that would be 40 feet to the range.

I guess I don't quite understand why that would matter unless the appliances were all in somewhat of a series?

-- Joe
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Old 01-30-2012, 01:25 PM   #6
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Propane pipe size


Quote:
Originally Posted by anesthes

Yeah, that would be 40 feet to the range.

I guess I don't quite understand why that would matter unless the appliances were all in somewhat of a series?

-- Joe
Because you would get too much pressure drop and, therefore, not enough gas to your farthest appliance.
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Old 01-30-2012, 01:58 PM   #7
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Propane pipe size


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Because you would get too much pressure drop and, therefore, not enough gas to your farthest appliance.
Ok. Right. I think I've got it now, pressure drop per foot based on the diameter.

I'll read through the sizing again.

What is the risk of over-sizing?

-- Joe
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Old 01-30-2012, 02:02 PM   #8
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Propane pipe size


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Originally Posted by anesthes

What is the risk of over-sizing?

-- Joe
Money spent on larger pipe and fittings, which with black iron fittings isn't that much. Over sizing isn't a bad idea if you ever decide to add more appliances.
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Old 01-30-2012, 03:45 PM   #9
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Propane pipe size


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Originally Posted by hvac benny View Post
Money spent on larger pipe and fittings, which with black iron fittings isn't that much. Over sizing isn't a bad idea if you ever decide to add more appliances.
Sounds like what I should do then. I'll just run 1". If my calculations are correct, 1" would be fine for 80 feet (double the length) at 300,000 btu. 1" black is under $1 per foot. Not a huge savings, maybe 25 cents per foot tops over 3/4".

TarheelTerp edited my quote and changed my range size from 80k to 110,000 btu.. Is that something normally done, when you guys size a system do you assume a 110k range/oven ? I know a lot of commercial ranges happen to be 110k.


Thanks folks!


-- Joe
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Old 01-30-2012, 11:49 PM   #10
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Propane pipe size


I checked my code book, and based off of your numbers, I would run a 3/4" (40' code zone = 306MBTUH@11"w.c.) main trunk, and 1/2" (40' code zone @ 182MBTUHA@11"w.c.) feeds to the appliances. These sizes would work for your appliances and longest measured run up to 100' according to my code book (Canadian Standards Association B149.1). Any pipe under 2" is like working with spaghetti, but for a newbie such as yourself, the smaller 3/4" and 1/2" pipe will be much easier to work with.
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Old 01-31-2012, 07:34 AM   #11
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Propane pipe size


Quote:
Originally Posted by hvac benny View Post
I checked my code book, and based off of your numbers, I would run a 3/4" (40' code zone = 306MBTUH@11"w.c.) main trunk, and 1/2" (40' code zone @ 182MBTUHA@11"w.c.) feeds to the appliances. These sizes would work for your appliances and longest measured run up to 100' according to my code book (Canadian Standards Association B149.1). Any pipe under 2" is like working with spaghetti, but for a newbie such as yourself, the smaller 3/4" and 1/2" pipe will be much easier to work with.
That was my original plan, which comes out to 175MBTU @ 100 feet or 287 MBTU at 40'. Here is what I was/am confused with.

When the system T's off like mine does, you still only calculate for the longest run? For example, if I go 40 feet to the left, and 30 feet to the right, I just use the 40 foot column for my calc, not add the 40 + 30 ?

Thanks!

-- Joe
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Old 01-31-2012, 09:48 AM   #12
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Propane pipe size


You measure from the source, which would be the regulator, to the farthest appliance, and this will give you the code zone. From there, you use the btuh being carried by that particular section of pipe to determine pipe size. So, before the tee, the pipe will carry your total load (110+70+36=216) you choose whichever pipe size in the 40' code zone will carry at least 216 mbtuh. After you tee off to an appliance, the pipe can reduce to carry the total load minus the load of the appliance that has been teed of to. Finally, each pipe serving an appliance individually can be sized to the load of the appliance, still using the 40' code zone.

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