I need someone who can bring all the info together on how this is done.
I know this:
You need the btu requirements for each gas appliance. You can pull this info off each appliance.
You need a table like this: http://www.tanklesswaterheaters.com/sizingtable.html
For natural gas, the top two tables in the above chart are what I think matter. The numbers in the chart don’t appear to be Btu load carrying capacity, they appear to be in something else.
The idea appears to be add up all your appliance Btu requirements, and match that to pipe size/length that will deliver that amount of Btu’s.
Can you also expound on piping layout, such as trunk lines with branch lines and when to run home runs. Also I think I have also seen, maybe I am wrong, a 3/4″ line followed by much bigger pipe down stream-is this something that is done as well.
Thanks in advance.
Replies
I hate to use the default CYA answer, but a trained and licensed professional should know the correct sizing protocols (I say "should" because I have seen it done incorrectly, leading to combustion appliances that are "starved" for fuel). In most jurisdictions, gas lines can only (legally) be installed by licensed individuals.
Done wrong, and the appliances may not operate as it (they) should, and of course you could easily blow the house off the foundation and kill everyone inside. Also, most states/municipalities have electrical bonding requirements for gas lines, particularly for flex lines.
Yeah sure, but the knowledge is generally pretty basic. This is somethhing that should be readily available, but having done some google searches, came up empty handed. Hoping that an experienced plumber will step up and share some info.
" pretty basic" !!!!!!
Where do you get that from. Pipe sizing is done wrong so often it can't be basic.
Basic!!! Yet you ask for a plumber! You should be asking for a gas fitter! A plumber MIGHT be a gas fitter.
Maybe it's too early for me. Sheeshroger
Plumbers do it all & fitters do what they are told ;-)
What is up with you dude? If you have not anything informative or constructive to add to this thread then please resist posting boorish comments and hijacking this thread with your inane stories.
Your ignorance is only surpassed by your ignorance.roger
The charts in the link provided are cubic feet per hour.
1,034 btu's = 1 cubic foot of natural gas.
I use 1,000 for easier math ;-)
"Home runs" to each appliance is rarely if ever done.
Generally you have a main trunk line & branch off to each gas outlet.
Branch lines are sized from the appliance all the way back to the meter, not back to the trunk line.
Smaller pipe feeding a larger pipe is only done at the source, wether it's a meter or a regulator.
We do a lot of homerun using tracpipe, and when running black, I always size longest run and load to load, to see which is more cost effective.
I can also use copper and galvanized.
When you say "homeruns" do they go in opposite directions or a bunch of parallel lines.
My house for example has 25' of pipe before the first tee & a total of 6 outlets they are sized at 1" due to length.
125' of parallel 1" lines is not cheap when using CSST & labor intensive if using IPS.
Side note, you heading to Edmonton for that monster project, I hear they are looking for about 15,000 workers.
Usually 1" black into the furnace room. Csst off of a header, black- main and branch. Every thing in the furnace room is usually black. Fireplace, stove etc is csst.
Same with copper and pex. I like the look of copper, straight and parallel. Once I'm into the ceiling, homerun pex.
Hadn't heard of a call. Staying put here. I like being at home at night.
When copper is a reasonab;e price our company is pushing it heavy for gas lines which just got approved for gas a few years ago.
They are really big on propress¯, I can see that for gas, but water & hydronics I have come to the conclsion it sucks----- I should re-open my business & do nothing but propress repairs when in 5yrs it all fails.
"1,034 btu's = 1 cubic foot of natural gas."Thank you for that nugget of information."Smaller pipe feeding a larger pipe is only done at the source, wether it's a meter or a regulator."Can you explain what this is all about. I read Popawheelies posts and your response to them, but it did not clarify, for me, why this is done. I know that if you were running water supply lines, placing a 1" pipe downstream of a 1/2" pipe would not do anything for your pressure, as the 1/2" pipe would act as a bottle neck. But this does not seem to be case with gas?In regards to the chart: 1/2" pipe, 10' long delivers 174 cubic feet per hour= 180,000 btu per hour. Way more than enough for a gas oven that requires 11,000 btu's per hour(?) to operate.If you have a 20' 3/4" trunk line, followed by a 10' 1/2" trunk line, you add the total of the two lines = 260,000 + 180,000= 440,000 btu's per hour- something is not right with this, because the more branch lines you add, the less btu's you should get, not more. What is the proper calculation for this then.Thanks
Edited 10/25/2009 10:20 pm ET by yojimbo2
Look at it this way.
Most meters are 3/4" & 1", can't connect a 1-1/2" pipe to a 1" meter so you would have a smaller pipe to make the connection.
& yes it's done with water as well 1" line fed to house comming from a 3/4" meter.
& you're right that it "will not increase pressure", but it will have less restriction so you can get more flow.
But you cannot do this in the middle of a run of pipe & say that it sized big enough for the demand required.
Hey thanks for that info, makes sense. Can you answer the part about the calculating btu's with branch and trunk lines as well?
I could answer it, but I would just be saying the same as RD for the most part.
FYI, <<1,034 btu's = 1 cubic foot of natural gas.I use 1,000 for easier math ;-)>>The heating value of natural gas varies widely due to its underground source, anywhere from 800-1100 BTU per "standard" cubit foot at sea level. I agree that 1,000 is a "good round number." ;-)
I'm no plumber/HVAC mechanic so this will be a very rudimentary post.... I'm just relating some practical experience,,,
What I've observed and the way it was explained to me was that for common single family residential applications with a 2 lb meter, (psig) 3/4" is normally adequate for most anything. Small to medium commercial applications may have a 5 lb meter (psig) in which case 1" or larger is run.
I guess if you live in a 12,000 sq ft house it could be more complicated....
I have yet to see a house with 2psi natural gas distribution.
.5psi or about 6 to 10 inches on the water column is what I have seen.
Larger psi means smaller pipe required.
Where I am in BC I rarely see low pressure systems. They are mostley 2lb systems. When I did a house that I bought here and ordered a low pressure meter, the first thing the gas person said was "you must be from back east" which I was. Out here we do have a choice which is really handy. Back in Ontario I don't think it was possible to order a 2lb system.roger
I've done a lot of 2lb & 5lb systems, but I'm more on the commercial side of things.
When I first moved out here I worked for one of the biggest mechanical contractors who had I believe over 100 plumbers. I was doing a 5lb job and was in the process of setting it up to do a pressure test on the lines. The foreman(who had his "A" gas ticket which is the highest)came over to me and asked what I was doing. When I told him he said not to pressure test it but just use the 5lbs to do a leak test.
Oh, I forgot.............he was a plumber also;)roger
LOL
I've got to use some nice digital gauges that would detect a leak using less than 1lb test pressure, damn pricy things they are.
Most of our gas systems (excluding CSST) we test @ half of whatever gauge we have on hand over 60lbs.
We found out the hard way what happens to 2"CSST when hit with 50psi------ Viagra got nothing on that.
You UA?
Edmonton is calling for a bazillion pipe workers.
No I'm not in a union.They usually need pipe fitters not gas fitters. The union office in Edmonton I believe is the largest in Canada.
I left Ontario to get away from the cold so Fort McMurray doesn't seem to have the same attraction as here. I like money but not THAT much.roger
From what I have heard they need pipe workers as the call is for pretty much anyone who knows how to join pipe, or move it from point A to point B.
I've heard two different things on the money side of it from 90K for 6 months to 10K every 45 days. As you can see those don't equal each other.
If I was hungry & had no work I might be interested, but I'm not the young single gun I used to be.
I would have to be starving with no unemployment left to consider working in 60 below for 80 grand a year.
Don't believe everything you hear. They do make good money (though not as much as you might think)but you must be in the union. They take their own local first which if I remember has over 10,000 members then they take from other unions. Their piping is huge and is strictly controlled. A welder doesn't touch the pipe, they only weld it. A fitter fits the pipe but a labourer actually moves the pipe THEN the welder welds it.
Most of the guys I knew lived on-site and were housed and fed but most guys piss their money away. Very few guys come out with money in their pocket.roger
Neighbors kid is a fitter. He was making 160,000 -180,000 doing QC. Included sub and overtime. Most fitters make less.
The 80K sounded about right for straight time on a UA job.
The 90K for six months had to have a buttload of OT & probably some perdiem.
My hall is ahving a meeting on it next Saturday for those that are interested------ I won't be there.
I've wondered about the size of gas lines in my house.
I have 3/4" coming off the meter and then as it enters the house it jumps up to 1".
The one inch goes across the utilty room where it braches off to feed a furnace and a water heater with 3/4".
I think I've seen this before.
Is the larger size there for a reason?
Will Rogers
You probably have a 3/4" meter set, & the length & load of the system require a 1" line, that is quite common.
Let me get this straight. I'm not getting more gas through the 3/4" line that it will move.
But, the 1" "trunk" has some volume in it because of length that might be added later?
So if someone decided to put another gas appliance in they would have 1"?
Right now the 1" trunk is about 15' long across the utility room.
I was thinking ( I know it's dangerous ) that the 1" would help when one appliance was on and another came on. Does that make sense?
"There are three kinds of men: The one that learns by reading, the few who learn by observation and the rest of them have to pee on the electric fence for themselves."Will Rogers
But, the 1" "trunk" has some volume in it because of length that might be added later?
You're losing me with that one.
The size is usually for what is there, sometimes we run larger for future expansion of the system.
I was thinking ( I know it's dangerous ) that the 1" would help when one appliance was on and another came on. Does that make sense?
Yes, the larger pipe has less restriction.
Lets say one fixture is already on and another bigger fixture comes on.
Could the bigger fixture coming on drop the pressure momentarily enough to mess with the other one.
Just for a moment when it comes on?
I'm not saying it's right. I'm just saying. Do some fixtures shut down if there is enough drop in the gas delivery?
I was just wondering. I'm probably over thinking this. "There are three kinds of men: The one that learns by reading, the few who learn by observation and the rest of them have to pee on the electric fence for themselves."Will Rogers
They don't "shut down" the flames become smaller and the colour changes because of whole bunch of things, and then because the combustion is all wrong you get carbon monoxide and you all die.
But..........I could be over-thinking all this;)roger
That's it, I'm switching to all electric right now!"There are three kinds of men: The one that learns by reading, the few who learn by observation and the rest of them have to pee on the electric fence for themselves."Will Rogers
Why? didja know it's possible to get CO from an electric oven?
I didn't know that."There are three kinds of men: The one that learns by reading, the few who learn by observation and the rest of them have to pee on the electric fence for themselves."Will Rogers
There are some gas appliances that will shut off if there is not enough gas flow, but that's rare. Having a flame that fets smaller would be more common.
If a fixture comming on line is reducing the amount of gas delivery to another appliance, then the system is too small for the demand & sized incorrectly.
"I was thinking ( I know it's dangerous ) that the 1" would help when one appliance was on and another came on. Does that make sense?"
Won't work, the total c.f. comming from your meter is going to be less as it travels through your pipe and picks up the fixtures as it goes by, if the larger pipe is not sized with the whole system its rating is the same as the smaller pipe it's connected to.
"If all else fails, read the directions"
Right now I have 3/4 coming into the basement.
Then it steps up to 1" for 15'.
But I wanted to add a fixture across the house (100').
Would I get more gas with 1" or 3/4" if I ran it 100' ?
And, if in the future I added in more fixtures, I would already have the 1" in place.
I just got a new meter because they had to move it. I asked if they could bump it up one size. They said it was not needed.
I think I'm fine but just wondered about the 1".
"There are three kinds of men: The one that learns by reading, the few who learn by observation and the rest of them have to pee on the electric fence for themselves."Will Rogers
Would I get more gas with 1" or 3/4" if I ran it 100' ?
1" will restrict the gas flow less than a 3/4" line no matter how long the line is ran.
But neither pipe will produce "more gas".
You need to run the full sized demand all the way back to the meter minus a nipple the same size as the meter set to connect a bell reducer to.
Thank you!"There are three kinds of men: The one that learns by reading, the few who learn by observation and the rest of them have to pee on the electric fence for themselves."Will Rogers
The only place a gas line might jump up in size is at the meter.
The gas company is only going to say the meter is adequate is pertaining to your existing fixtures; they will not assume what you may or may not hook up in the future.
Without knowing the load from your future fixtures you are playing a guessing game.
If 1in. is comming from the meter you might as well continue with it, you may luck out and have it work in the future.
"If all else fails, read the directions"
Your installation is commonly done, and it works fine.
The reason why it works is that the short section of 3/4 pipe offers very little restriction (friction). In a low-pressure system, a 3/4 pipe that's only 10' long will deliver 273 cu ft/hr (or about 273,000 BTU/hr). Incidentally, only the gas company can give you the accurate conversion factor for cubic ft to BTU capacity; generally, you're safe if you figure 1 CFH = 1000 BTU, but this can vary by 10% either way.
Now, supposing that your 1" line serves appliances that add up to 175,000 BTU/hr, that 1" line could run for a total distance of 70' and still deliver 179,000 BTU/hr, which the short 3/4 line is capable of carrying. If the 3/4 line were 70 ft long, it would deliver only 95,000 BTU/hr at its far end.
In response to one of your later posts, where you asked if a larger line can temporarily provide a small boost in gas capacity, the answer is: yes it can.
This is because the larger line acts as a reservoir for the compressed gas, much like a pressure tank on an under-sized water system can supply the extra volume needed for operate a flushometer on a urinal. In the case of the pressure tank, it's the compressed gas (air in the top half of the tank) that gives the extra boost. Between flushes, the pressure tank fills again, but, of course, it won't supply the extra flow continuously.
Interestingly, some manufacturers of large, commercial water heaters insist that at least 10' of 3/4 connector line be installed between the appliance and the main line in order to give that extra boost for the initial firing. If you don't the appliance will fail to fire, and will flash a code that indicates insufficient gas flow.
Thanks rdesigns. I once replaced the main water line for my house using used copper I got off of a commercial job.
The copper was 1 1/4" and was about 90' long.
A soldered up the 90' and pressure tested with water it before I dropped it in the trench.
After the test I open up one end and was amazed at how much water came out of the pipe. It flashed through my mind that I hadn't disconnected the other end. It was that much.
"There are three kinds of men: The one that learns by reading, the few who learn by observation and the rest of them have to pee on the electric fence for themselves."Will Rogers
I assembled a list of appliances with an rough average of Btu consumption:40 gal gas water heater: 40,000 btu'sOven/cooktop: 16,000 for the oven, 12,000 for each burner, so 70,000 btu's.Vented fireplace logs: 50-90,000 btu's
Unvented fireplace logs: 10-30,000 btu'sGas dryer: 15,000 btu'sComes to about 270,000 btu's if everything is on at once. Single family home, under 1600 square feet.
Assuming that you're using black iron pipe, and that you use the "longest run" method of sizing your line, the next step for you is to measure the distance from the meter to the farthest appliance--say it was the gas dryer @ 15k BTU's--the chart you posted shows that you could use 1/2" pipe if the distance from the meter were no more than 70 ft.
Say the next section of pipe (working back toward the meter) serves the kitchen range @ 70k BTU; this section of pipe needs to be sized for both the range and the dryer, or 85K BTU's. Staying on the 70 ft. column, you see that you would jump to 3/4".
Say the next section serves the 85k that we just sized for, plus the water heater @ 40k--a total load on this 3rd section of pipe of 125K. Again, staying on the 70 ft. column, you see that 3/4 is still good for 127k.
Keep going this way all the way back to the meter. You now have your homerun, or main line sized.
The code allows you to use one of two methods to size branches that were not previously sized in the homerun calculation.
1) you can continue using the 70 ft. column for each branch, which will usually result in oversizing to a certain extent, but it's usually no big deal--you might end up running 3/4 instead of 1/2 for the branch.
2) the branch method allows you to size each branch based on its distance from the meter, but you have to size the main line (or homerun line) based on the load imposed by the branch load.
For a DYI'er, I recommend #1, because it costs very little , if anything, more, and always keeps the inspector happy.
I totally got the 1st half of your post. Thank you, thank you, thank you."1) you can continue using the 70 ft. column for each branch, which will usually result in oversizing to a certain extent, but it's usually no big deal--you might end up running 3/4 instead of 1/2 for the branch."70' to the farthest appliance, and then I add more footage of the 3/4" pipe for additional branch lines as I approach the meter. Lets say I end up with 110 feet of pipe run total-including both trunk and branch lines. I am okay, just as long as I meet the btu requirements for all the appliances. I think I understand this."2) the branch method allows you to size each branch based on its distance from the meter, but you have to size the main line (or homerun line) based on the load imposed by the branch load."Not clear on this part. How do size the main line base on the "load" imposed by the branch line? Not clear on the "load" imposed part, or the whole of #2. I am almost there.
"70' to the farthest appliance, and then I add more footage of the 3/4" pipe for additional branch lines as I approach the meter. Lets say I end up with 110 feet of pipe run total-including both trunk and branch lines. I am okay, just as long as I meet the btu requirements for all the appliances. I think I understand this."
If 70' were the longest run, as in my example, you DON'T add more footage for branch lines. The charts are designed to give adequate supply to everything else if you use the column that is equal to the longest run.
In the process of sizing the main line (which is the longest run) all the way back to the meter, let's say there's a branch line that serves two appliances--say gas logs (60k BTU) and a gas fireplace (40k BTU). This branch with its two appliances would impose a load of 100k that would have to be fed by the main line.
The main line section of pipe that serves this branch would have to sized (using the 70' column) for the BTU requirements, not only for the branch load of 100k, but also for the load of all appliances beyond the tee that serves the branch line.
Once the main line is sized, you have two options for sizing this branch line with the logs and the fireplace.
Let's say the fireplace is 50' from the meter and logs are 20'. By using method #2, you could go back to your gas table and begin sizing the sections of pipe in the branch line. Starting at the farthest appliance on the branch, the fireplace, you go to your chart, and using the 50' column, see that 1/2" pipe is good for 73k, so that's the size of the first section. The next section will need to feed both appliances (100k), so, staying on the 50' column, you see that you need 3/4 for the branch line that runs from the main line to the tee that serves both appliances. The sub-branch that feeds the logs (60k) could be 1/2" since the 50' column shows that you're good for 73k.
OR, using mehtod #1, you could size all the lines in the branch section, including sub-branches to the appliances, by using the 70' column. In this example, you would see that the pipe sizes would be the same whether you use method #1 or #2.
So, like I mentioned in the earlier post, it's usually simpler and more sure to meet with the inspector's approval to use method #1, where you stay on the 70' column for all pipe sections. There are many plumbers and gas fitters who use no other method, and there are some jurisdictions that allow no other.
Hey, I want to thank you for your patience in leading me through this concept until I understood it.
My pleasure.
But I think now you might understand one of your responders (#7) who got a little testy about the idea that gas pipe sizing is simple. Not saying his response was well-mannered or helpful, but he's right in saying that many plumbers and gas fitters don't quite get it when it comes to using the charts right.
It's like anything else--simple once you learn it.
Like the farmer who told the plumber as he watched him work: "I think my boy could do that if he had the tools and knew how."