Gas pipe sizing

[North Jersey]

I've decided to run a couple new propane branches to add a dryer and a range to my home.

I would appreciate input on a couple of questions:

1. In the process of evaluating the gas distribution system, I noticed the first stage from the tank is only 1/2" copper tubing, approximately 190 feet in length. As far as I can tell, the capacity of that length of tubing at 10 psi is only 209 MBH. Currently, the total maximum appliance load is 296,000 BTUs (110, 88, and 60 from furnaces and 38 from a water heater). Ought I to install a 15 psi first stage regulator to improve this situation?

2. I noticed the first several feet of pipe beyond the second stage regulator is 1/2" black pipe. I'll be adding at least 99,000 BTUs of appliances to the 296. Should I use a close nipple and a reducer to step up the pipe size to 1-1/4?

 

[Reach4]

Propane at 10 psi? At that pressure, the BTUs available thru 1/2 inch copper would be a lot. In a house, the propane pressure is usually regulated down to about 11 inch water column nominal. That would be about 0.4 psi. 14 inches of water would be about 0.5 psi.

When you say MBH, do you mean thousand BTU/hour or million?

I am not practiced in propane or other BTU calculations, but you might want to confirm your info.

 

[Sponsor]

 

[wwhitney]

1. In the process of evaluating the gas distribution system, I noticed the first stage from the tank is only 1/2" copper tubing, approximately 190 feet in length. As far as I can tell, the capacity of that length of tubing at 10 psi is only 209 MBH.

It's 1/2" OD, not 1/2" nominal (5/8" OD)? If so, then you are correct. 5/8" OD would be 426.

As to how to deal with it if is too small, I don't really know anything about propane (other than how to read the pressure drop tables), so I don't know if 15 psi is viable, or if you'd be better off upsizing the 190' of pipe.

Also, that table is based on 10 psi from the regulator and 1 psi drop. I believe that for natural gas/propane, the the pressure drop varies as approximately the square of the flow rate. So if you are at twice the tabular value, you'd have about 4 psi pressure drop when everything is running. The table implies that's undesirable, but I'm not clear on what would actually happen if you supply only 6 psi to your second stage regulator.

2. I noticed the first several feet of pipe beyond the second stage regulator is 1/2" black pipe. I'll be adding at least 99,000 BTUs of appliances to the 296. Should I use a close nipple and a reducer to step up the pipe size to 1-1/4?

From a different table, if the second stage regulator is set to 11" w.c., and the allowable pressure drop is 0.5" w.c., then 10' of 1/2" schedule 40 pipe has a capacity of 291 kBTUs/hr. So at present if you have 3' of 1/2" pipe there, that's using up 30% of the allowable pressure drop for your current load.

In other words, the value of "several" is important here; 1' is probably OK but 5' would be very poor. It does seems like if you are going to 395 kBTUs/hr you'd want to eliminate any 1/2" iron pipe after the second stage regulator.

Cheers, Wayne

PS Let me put in a word for considering using less propane and more electricity, as fossil fuels are (very slowly) on their way out. I.e. instead of going to 395 kBTUs/hr, substitute electricity for the new appliance, or for one of the existing appliances, to keep your propane demand from increasing. That way you won't have to change your propane infrastructure.

 

[wwhitney]

As to how to deal with it if is too small, I don't really know anything about propane (other than how to read the pressure drop tables), so I don't know if 15 psi is viable, or if you'd be better off upsizing the 190' of pipe.

A couple further comments:

The table says 1/2" OD copper at 10 psi with 1 psi pressure drop can carry 401 kBTUs/hr for 60 ft. So at 190 ft you'd have a bit over 3 psi pressure drop.

As to increasing from 10 psi to 15 psi, I'm still not sure about that, but it would depend on the capabilities of the 2nd stage regulator. I.e. based on the table allowance of 1 psi drop out of 10 psi, the typical 2nd stage regulator can deal with incoming pressure variation of 9-10 psi. If 7-10 psi is too much variation for it, then the question is whether a different 2nd stage regulator could handle 12-15 psi as the incoming pressure range. [That is, bumping to 15 psi shouldn't change the pressure drop.] If 3 psi variability on the inlet of the 2nd stage regulator is just too much, the only solution is to enlarge the pipe or reduce the demand.

Cheers, Wayne

 

[North Jersey]

Propane at 10 psi? At that pressure, the BTUs available thru 1/2 inch copper would be a lot. In a house, the propane pressure is usually regulated down to about 11 inch water column nominal. That would be about 0.4 psi. 14 inches of water would be about 0.5 psi.

When you say MBH, do you mean thousand BTU/hour or million?

I am not practiced in propane or other BTU calculations, but you might want to confirm your info.

Yes, the first stage regulator steps the tank pressure down to 10 psi.

I mean thousands of BTUs.

It's 1/2" OD, not 1/2" nominal (5/8" OD)? If so, then you are correct. 5/8" OD would be 426.

As to how to deal with it if is too small, I don't really know anything about propane (other than how to read the pressure drop tables), so I don't know if 15 psi is viable, or if you'd be better off upsizing the 190' of pipe.

Also, that table is based on 10 psi from the regulator and 1 psi drop. I believe that for natural gas/propane, the the pressure drop varies as approximately the square of the flow rate. So if you are at twice the tabular value, you'd have about 4 psi pressure drop when everything is running. The table implies that's undesirable, but I'm not clear on what would actually happen if you supply only 6 psi to your second stage regulator.


From a different table, if the second stage regulator is set to 11" w.c., and the allowable pressure drop is 0.5" w.c., then 10' of 1/2" schedule 40 pipe has a capacity of 291 kBTUs/hr. So at present if you have 3' of 1/2" pipe there, that's using up 30% of the allowable pressure drop for your current load.

In other words, the value of "several" is important here; 1' is probably OK but 5' would be very poor. It does seems like if you are going to 395 kBTUs/hr you'd want to eliminate any 1/2" iron pipe after the second stage regulator.

Cheers, Wayne

PS Let me put in a word for considering using less propane and more electricity, as fossil fuels are (very slowly) on their way out. I.e. instead of going to 395 kBTUs/hr, substitute electricity for the new appliance, or for one of the existing appliances, to keep your propane demand from increasing. That way you won't have to change your propane infrastructure.

The tubing is unfortunately 1/2" OD (confirmed with calipers).

I would love to upsize the tubing with some cheap poly. The material cost would be negligible. That said, the underground tank is artfully concealed beyond my front lawn. It also traverses septic components. I am relcutant to excavate that area.

Between the second stage regulator and the first branch, I have about 7.3 feet (including equivalent length of two elbows and a tee). Between the regulator and the 3/4" branch (236,000 BTU maximum load), I have a total equivalent length of about 11.5'.

Whether or not I can find a pair of commercial regulators at 15 psi and 11 wc, I'm pretty sure I need to remove all of that 1/2" pipe. I'm thinking a 1-1/4" manifold with CSST to the two existing branches (eliminating the elbows and tees), and a 1-inch CSST branch for new and future appliances would fit the bill.

I'm actually adding water-to-air heat exchangers to each of my furnaces, so that I can use coal-fired hydronic heat, which is much more economical than the alternatives. I live very close to anthracite country, and I can stockpile a lifetime of fuel for very little money. A Catholic seminary in the area was offering 38 tons of coal for free to anyone who could remove it from the basement. I'm also installing a couple of heat pump units, so I'll have three options for central heat. Heat pumps alone are really only practical for the shoulder seasons in this climate.

 

[Reach4]

PS Let me put in a word for considering using less propane and more electricity, as fossil fuels are (very slowly) on their way out. I.e. instead of going to 395 kBTUs/hr, substitute electricity for the new appliance, or for one of the existing appliances, to keep your propane demand from increasing. That way you won't have to change your propane infrastructure.

Keep the propane infrastructure for powering that whole house Generac for when they shut down the electricity for when the winds are high or for rolling blackouts.

 

[North Jersey]

Considering future expansion, (another 300,000 BTUs for a generator), I suppose I'll have to bite the bullet and tear up the yard. I don't think the benefit gained by installing a 15 psi regulator would be a long term solution. While I wait for the snow to melt, I'll remove the 1/2" pipe and replace it with 1-1/4". That 1/2" pipe passes through four or five inches of granite veneer. I hope I can widen that hole in the stone without cracking it. I've found some diamond milling bits with a 5/8-11 thread for use on an angle grinder.

 

[Fitter30]

There is a lot more than just raising the line pressure of the first stage regulator. Rate of vaporization of the size of tank. The varying pressure of the tank and the pressure out of the regulator. Summer tank could be 150psi winter 50lbs output of reg will vary as well as tank vaporization. All the 1 st regs I've seen have been set 10 lb for home heating. Lp for engine fuel is different pressure.

https://www.google.com/url?q=https://babfar.com/wp-content/uploads/2016/12/BABFAR-Vaporization-Tables.pdf&sa=U&ved=2ahUKEwjRveblxeP8AhUakokEHYkCD_sQFnoECAwQAg&usg=AOvVaw3gW4RvyjAvf2_UPU3V2e-P

 

[North Jersey]

I have a 1000-gallon underground tank, so I expect it to be good for well over 500 MBH at the coldest time of year and at a 10 percent fill.