Gas Pipe sizing for new outbuilding

Rainman13

Hello everyone, new here and was hoping to find some help with sizing a gas line for my new pole barn.
The meter on my house is rated at 425 CFH (it was upsized when I installed the generator). The regulator is at 6-8 IWC. The outlet of the meter is 1.25 inch. From there, it reduces to 1inch. After the reduction, there is a tee with one side going into the house for all of the appliances, and the other side of the tee goes to the generator, about 10 feet away. My plan was to tap into the line that supplies the generator and run it to the new outbuilding, just under 200 feet away. My questions are:

Can I increase the size of the line going to the outbuilding (possibly to 1.5 or 2) after the connection to the generator? Will this even help, since the larger line would be supplied by a smaller one?

If I can increase the size of the line to one that is larger than the one coming off the meter, would I be better off replacing the short (10 foot) section of line going to the generator with the larger size line, then continuing to the barn?

The charts I am looking at have me landing between a 1.5 and 2 inch line to the pole barn. Will putting the larger line in cause any other problems?

The generator uses 309 CFH at 100%, and the furnace in the pole barn will use about 60 CFH. The only time the two may run at the same time is when the generator is in test mode (5 minutes every Saturday). Other appliances in the house (furnace, HWH, dryer, stove), however, may be running at the same time as the barn furnace.

Thanks for any help!

EBEBRATT-Ed

You look way undersized to me. The pipe to the pole barn needs to be tapped in right at the meter outlet not into the generator pipe. It's questionable wether the meter can supply the load that is on it without an unreasonable pressure drop.

The big question is what is feeding the meter high pressure(over 1 psi) or low pressure 6-8"wc.

Mad Dog_2

You always want to design, especially with Gas for worst case scenario...everything running simultaneously.  Unlike, Potable water, not obeying the laws and rules for natural gas could cause combustion and Dangerous Carbon Monoxide issues.  You need to look at The N.F.P.A. Fuel gas guidelines for proper sizing and distances.  This is usually a Master Plumber's Responsibility to size and run out the piping.  What are you planning for the 200 Foot Run?  Poly Pipe buried?  Mad Dog 🐕 

Rainman13

So maybe I didn't explain it correctly in my post. When there is no power, the generator will not power the barn. So, the barn furnace and generator will never run at the same time. The end result is exactly what I have now, which functions just fine. My question is, can I tap into the generator line (after the generator) with a larger line? Will that provide any more pressure/volume than tapping that line with the same size pipe? Would I benefit at all from using a larger line from the meter to the generator AND the barn? Mad Dog 2 I was planning on burying poly line out to the barn, just didn't know if I would benefit from using 1.5 or 2 inch if there is 10 feet of 1 inch off the meter before it. I might try to draw a diagram so I can explain it better. Thank you both for the replies, I appreciate it.

EBEBRATT-Ed

No. The line for the barn must be tapped in as close to the meter outlet as you can get it regardless of the pipe size of the meter outlet. Tapping the gen pipe is not a good idea.If the meter outlet is 1 1/4 that's where you tap in and it should be as close to the meter as possible.

As far as the size pipe to the barn if the input to that appliance is 60cfh/hr and it's a 200ft run that's how you size the pipe and you should allow for any fittings in that run. Since you only have 6-8" wc you cannot afford much pressure drop in the pipe to the barn so I would be on the conservative size wise.

mattmia2

unless you interlock the generator and new load so they can't run at the same time during automatic tests and maintenance and such you need to size for the total load. the existing load on the meter is marginal but it somewhat depends on how the service regulator is set

Rainman13

Here is a drawing I made showing what I have now and what I think may work, if I am understanding mattmia2 and EBEBRATT-Ed correctly. I may even be able to go down to 1.25 after the generator for the rest of the run to the barn.
What I wanted to do was put a separate service to the barn, but the gas company wants about $4k to come 30 feet off the road, so I'm exploring other options, including this, or a propane tank for the barn. I appreciate your feedback!

Mad Dog_2

Listen to the guys. I  know what you WANT to do but were telling you not a good idea. In NYS and NYC Meter, piping is designed for all appliances possibly coming in at once. If this is hardly used, think about to a Second gas meter just for the pole barn. Blowing up the gas piping to larger sizes, within reason is common to provide a "reservoir" volume of gas for hungry appliances, but it all emanates from your street service gas pressure in PSI & Inches of mercury.  H.P. gas can be jacked up by the gas utility at regulator if more gas is needed.  Gas meter sizing is based off of that and BTU load.  Just curious 🤔?  Are u tackling this yourself?  Mad Dog 🐕 

Rainman13

Thanks Mad Dog. What I WANT to do is have a system that works and doesn’t cause me problems. When I got the estimate for a new meter, I wanted to explore some options, this being one of them. I’m also going to discuss meter options with the gas company, or a propane tank for just the barn. Once I decide which route I’m taking, I’ll decide whether I can tackle it myself or not. I definitely know my limits. I appreciate the help from all of the guys. I definitely want to make an informed decision