What size gas line do I need for 200 000 BTU?

guys need some major help here. I am having a hard time sizing my needs for my gas line. I have a Reznor 200,000 btu heater that is 125' away from my tank. I would like to run the minimum size of gas line for cost reasons. Home depot says 3/4"(don't trust the knowledge) and my propane supply store says I can get away with 1/2". Does anyone have any tips on trying to calculate this?

 

That sucker takes 180,000 BTU in, and it's sensitive to pressure fluctuations from other devices turning on/off on the same branch. Ideally it would have it's own "home run" line teeing off very near the regulator/meter, and have sufficient BTU capacity for the length of the run (the length includes adding "equivalent length" of about 1.5 feet for every 90 degree fitting, whether tee or ell, along the path):



A gas dryer & cooktop together probably add up to 50-70,000BTU/hr, the water heater is 180,000 so you need a minimum of ~250K of capacity on a line that's shared, and any tees off to the other load is best located within a couple feet of the meter/regulator.

Half inch line won't cut it even at 2' of distance from the regulator, even though the connection to the unit is half-inch.

There no way 3/4" will cut it, even as a non-shared home-run to the meter unless the hot water heater is VERY close to the regulator.

Even 1" might not cut it if it's shared by other appliances and more than 20 equivalent feet of gas line from the regulator.

Most installations call for 1-1/4" gas lines, but as a non-branched home-run it's often possible to get there with 1" line.

The closest is the quote for 1", but measure it up yourself, and if it's anywhere close, have them re-quote it for 1-1/4" plumbed as a home run, so you don't have to worry about it mis-behaving when the furnace kicks on while you're in the shower.

Also, look at the BTU ratings of the furnace, dryer, and cooktop. Add it all up, including the 180K for the Navien, and compare it to the BTU rating of the meter & regulator. If you have a ridiculously oversized furnace (very common) there's some chance you'd be over the capacity of the regulator, which can also lead to some mis-behaviors if every thing is running at once.

It could be that none are getting it right, but some are clearly ded-rong.That sucker takes 180,000 BTU in, and it's sensitive to pressure fluctuations from other devices turning on/off on the same branch. Ideally it would have it's own "home run" line teeing off very near the regulator/meter, and have sufficient BTU capacity for the length of the run (the length includes adding "equivalent length" of about 1.5 feet for every 90 degree fitting, whether tee or ell, along the path):A gas dryer & cooktop together probably add up to 50-70,000BTU/hr, the water heater is 180,000 so you need a minimum of ~250K of capacity on a line that's shared, and any tees off to the other load is best located within a couple feet of the meter/regulator.Half inch line won't cut it even at 2' of distance from the regulator, even though the connection to the unit is half-inch.There no way 3/4" will cut it, even as a non-shared home-run to the meter unless the hot water heater is VERY close to the regulator.Even 1" might not cut it if it's shared by other appliances and more than 20 equivalent feet of gas line from the regulator.Most installations call for 1-1/4" gas lines, but as a non-branched home-run it's often possible to get there with 1" line.The closest is the quote for 1", but measure it up yourself, and if it's anywhere close, have them re-quote it for 1-1/4" plumbed as a home run, so you don't have to worry about it mis-behaving when the furnace kicks on while you're in the shower.Also, look at the BTU ratings of the furnace, dryer, and cooktop. Add it all up, including the 180K for the Navien, and compare it to the BTU rating of the meter & regulator. If you have a ridiculously oversized furnace (very common) there's some chance you'd be over the capacity of the regulator, which can also lead to some mis-behaviors if every thing is running at once.