Help with gas line riser chart

[JimJNJ]

Hey guys, I just discovered this site while planning a renovation of our laundry room and family room. Thanks in advance for any help or advice. We live in Bridgewater, NJ.

We're doing a lot of projects, but the one I'm currently stuck on is the extension of our gas line to our wood burning fireplace. We want to install a gas fireplace insert for convenience. We have natural gas in the house, which starts with a 1" line coming off of the meter and reduces down from there. There is a good spot to tee off the line and run an extension to our fireplace, and I am trying to calculate the various diameter requirements all the way back to the meter.

I intend to submit a permit, and I'm looking for plumbers to do the work, but it has been challenging because everyone is renovating these days, so I may end up running the gas line myself.

I put together this diagram and calculation as accurately as I could.

Looking at this guide for NJ and using the longest length method with the Pressure Drop = 0.5 in. w.c. chart, my concern is that I will need to increase the diameter of my gas line at the meter from 1" to 1.25". But I'm not certain that I'm doing it correctly. Here are my concerns:

- I need to confirm which chart is correct for my area using black iron pipe. Is that something the town would tell me?
- I could not determine the input BTUs for our range. Looking at it, only output values were listed, so the value I have in the sheet is a guestimate
- Should I use a different method of calculation vs. longest length? It looks like the branch length method has the same initial calculation for the pipe diameter at the meter
- Is there anything else I am missing?

Thanks a lot if you read all the way to this point.

 

[Breplum]

You are using sound methodology.
We use the .5" w.c. chart for normal residential gas as per Uniform Plumbing Code.
At 60' to your fireplace you have 259 CFH. at 70', 239.
It's too late (12AM pacific time) for me to remember interpolation, but, the code is generally overly cautious.
It presumes all other gas appliances running simultaneously for there to be any diminishment at all.
It'll work fine.

 

[Sponsor]

 

[wwhitney]

It would be helpful if your spreadsheet included the existing sizes, rather than just the calculated size.

As to the table, all you need to know is the pressure at the regulator and the allowable drop to the appliance. Those are usually 7" w.c. (0.25 psi, so under 2 psi) and 0.5" w.c. respectively, so that would be the only thing to confirm. If so for black iron pipe, use Table 402.4(2).

I'm guessing a bit, but I think you may have used Table 402.4(1), as I get that 1" is sufficient for 250 CFH at 62' using Table 402.4(2). So if that's the case, go back and redo your sizing, and let us know if there's still an issue. If there is:

The longest length method is a pretty conservative approximation of the exact answer. For example, before you add the fireplace, your longest length is 49'. The fireplace bumps that up to 62', which affects many of the sizing steps in the longest length method, more than is strictly necessary. So with the existing sizes and length, if the system would pass on the longest length method with the longest length at 49' (if the fireplace were 13' closer), then with a little extra-tabular computation you can just upsize the pipe from point 5 to the fireplace to account for the extra length of that segment.

Cheers, Wayne

 

[JimJNJ]

Thanks a lot guys. A diagram of the existing layout is on the 'Plumbing - gas' tab, but I added the sizes on the sizing sheet too.

I was using table 402.4(2), but I went to the next size up for 70', which at 1" only gives me 237 CFH.

It sounds like you both agree that I'm in pretty good shape with the existing lines and extending a .5" line for the fireplace. But how do I represent that when submitting my permit? My concern is my local township will want me to upgrade the lines to the letter of the law.

 

[wwhitney]

You don't need to go to the next size up, you can interpolate. Since 1" shows 257 CFH for 60' and 237 CFH for 70', for 62' you get 253 CFH.

Cheers, Wayne