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LP smaller diameter = higher pressure/BTUs? True??

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rbphhc
rbphhc Member Posts: 126
edited February 2023 in THE MAIN WALL
We just had the tech come by from propane supplier (nationwide chain) to determine correct LP line sizing for new tankless HWH, and he told me some stuff that seems wrong, want a second opinion.

- Current piping is as follows: big 1000 gal propane tank on the road, about 150' from the house. 1/2 inch copper running from tank to house regulator;

- Tech says existing regulator is good for 1.2 million BTUs. No need to change. Does that sound right?

- He said pressure on the house side of the regulator should be about 10 or 11 W.C. Doe that sound right?

- Thread coming off regulator is 1/2" NPT into 5/8" soft copper. That 5/8" trunk tees off and feeds a 1/2" line to a 6-burner gas stove and a Rinnai wall-mounted gas blower in one direction, and a 5/8" line to 2 gas-fired hot water tanks, a gas dryer, and a small upstairs gas 'fireplace' in the other direction (the 2 HWTs are getting replaced by a tankless + indirect).

- We asked the company to come in and upgrade the lines to accommodate the new tankless. My understanding was that they would need at least 3/4" coming off the regulator and feeding that 199k BTU tankless. (None of the other loads are huge, but they certainly add up.)

- Tech said no need to go 3/4", that larger diameter actually makes the propane 'lazier,' and that we should run a 1/2" line off the nearest tee to the regulator (about 2 feet away). He said that going smaller will keep the LP at higher pressure, and will be no problem for a 1/2" line to supply that 199k tankless *and* the gas dryer and small propane fireplace.

- Does that sound right? I thought we would need 3/4" off the regulator all the way to the tankless, with small 3/8" branches to the dryer and fireplace. (Stove and Rinnai blower are off a separate 1/2 branch going to the other end of the house.) Tech said there are actually 'more BTUs' in the 3/8 branch than in the 5/8.

I understand venturi physics, and that decreasing cross-section increases pressure, and vice versa, but isn't the KEY thing how big you go initially, off the regulator? Doesn't going to 3/4 off the regulator allow more flow to ALL the loads in the circuit? Doesn't staying at 5/8 limit the total BTUs we can supply to the house?

FYI, the distances here are not huge - from the regulator, about 2' to first tee; then, in one direction, about 6' to the stove, and an additional 30' to the Rinnai blower; in the other direction @ 12' to proposed tankless, @ 5' additional to the dryer, and @ 20' additional to the fireplace.

Help. Am I an idiot (granted), or is this guy smoking crack?

Main point is, we don't want to starve that new 199k tankless.

Thanks!
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Comments

  • mattmia2
    mattmia2 Member Posts: 9,959
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    The "lazier" part is not true, you get more volume through a larger pipe/tube.

    You would have to do the sizing calculations to figure out if 5/8" tube is adequate given the loads and the effective length of the run. Propane is distributed at a little higher pressure than natural gas and it is about 3x the energy content per volume of natural gas so it requires much smaller piping than natural gas.
    rbphhcMad Dog_2
  • hot_rod
    hot_rod Member Posts: 22,476
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    Is there one regulator outside and all the inside piping at 11". Or does each appliance have its own reg, so the inside pressure is higher, and reduced to 11" at each connection?

    Obviously the higher the pressure the more btus you move.

    The size of the tube and the amount of LP it carries has to do with pressure. A 3/8 line could in fact carry more BTUs then a 1" line, depending on the pressure. Use voltage as an analogy.

    Ever notice the pigtail on the reg at the tank? It's usually 1/4" or 3/8"copper and can carry your entire building seeing as it could be 100 psi or more in the tank.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    rbphhcMad Dog_2
  • rbphhc
    rbphhc Member Posts: 126
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    mattmia2 said:

    The "lazier" part is not true, you get more volume through a larger pipe/tube.

    You would have to do the sizing calculations to figure out if 5/8" tube is adequate given the loads and the effective length of the run. Propane is distributed at a little higher pressure than natural gas and it is about 3x the energy content per volume of natural gas so it requires much smaller piping than natural gas.

    Excellent. Thank you. Interesting about propane being 'higher yield.' Kind of like diesel and gas.

    Mad Dog_2
  • rbphhc
    rbphhc Member Posts: 126
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    hot_rod said:

    Is there one regulator outside and all the inside piping at 11". Or does each appliance have its own reg, so the inside pressure is higher, and reduced to 11" at each connection?

    Obviously the higher the pressure the more btus you move.

    The size of the tube and the amount of LP it carries has to do with pressure. A 3/8 line could in fact carry more BTUs then a 1" line, depending on the pressure. Use voltage as an analogy.

    Ever notice the pigtail on the reg at the tank? It's usually 1/4" or 3/8"copper and can carry your entire building seeing as it could be 100 psi or more in the tank.

    There is a regulator at the tank, and a signle regulator outside at the house. The tech was saying it was 10 to 11 WC off the regulator at the house.

    And I understand that you can push more BTUs through 3/8 than 3/4 *IF* the pressure is higher.

    BUT. That 11WC at the house is a ceiling, correct? And my understanding is that the larger you go with the *INITIAL* pipe, the more BTUs you 'let in' to the system. Is that right?

    So going 1" off the regulator allow more total BTUs into the house than 3/4". Which is more than 5/8". Which is more than 1/2". Etc. True?

    I don't know the numbers, but just for argument, say 400k for 1", 300k for 3/4" and 200k for 1/2". So no matter what size tubing I used down the line, I'm never going to move more than 200k BTUs if I only have a 1/2" trunk off the regulator. Right?

    Also, I'm guessing it matters what load is in a branch line *before* a given appliance? So say our trunk is 5/8" and 250k BTUs. Our 'south' branch is 1/2", which somewhat restricts the BTUs, correct? So now it's down to 200k? And then length further restricts it? AND. Having the 6-burner stove *before* the Rinnai wall blower further restricts it, assuming we're cooking? So what gets to the Rinnai? Maybe 150k at dinner?

    And in the 'north' branch, let's say we keep it at full 5/8", and go straight to the tankless. There's some reduction from pipe length, but it's only 15 feet ish, so, we're getting close to 250k at the tankless? (Again, I'm pulling these numbers out of my a**. Will check a chart shortly.)

    I'm assuming we don't want to feed the dryer and the fireplace *before* the 199k tankless, correct? Or does it not matter?

    What happens at the tankless (@ 15' and 5/8" away from the main tee) if someone is cooking at the stove (@ 6' and 1/2" away from the main tee)?

    Basically, bigger is better, right? Should we insist on at least 3/4" off the regulator, and run as short a line as possible, full 3/4, to the tankless? Then branch down from there to feed other appliances?

    Seems critical to get max volume to the tankless. Nothing else in the house is consuming nearly as much gas. (And, to be fair, that tankless is modulating/ condensing, and will rarely run at full capacity. So maybe it's only using 30k or 50k most of the time.)

    Thank for letting me sound this out!
  • Zman
    Zman Member Posts: 7,605
    edited February 2023
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    I am not sure if he is on crack, meth is so popular these days, and that would be my first guess.

    Seriously though, it is not all that complicated. You can use a chart like this: https://www.regoproducts.com/liquid-propane-gas/field-topics/sizing-propane-piping-systems/
    to figure it out. The code dictates that the drop is no more than 0.5"WC at the appliance. Keep in mind that when measuring the length of pipe there is a penalty for fittings, for example, a 90-degree elbow is equivalent to ~5 feet of pipe.

    Yes, Bigger is better!
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    rbphhcGGrossSolid_Fuel_Man
  • rbphhc
    rbphhc Member Posts: 126
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    ALSO, I paced off the distance from the house to the tank, and it's 59 YARDS, not counting the vertical sections. So something like 170'. Not sure how/if that affects things (like pressure available at the house).
  • hot_rod
    hot_rod Member Posts: 22,476
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    The first stage reg at the tank drops pressure to 10 psi. You can look up you reg to see it’s capacity, 2 mil isn’t out of the question.

    Next what is the tube size from the tank to the home, you mentioned 1/2” is that ID or OD. If it is 1/2 OD at that distance, that may limit you capacity.

    The link from @Zman takes you through the sizing steps
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Zman
    Zman Member Posts: 7,605
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    You likely have a dual regulator system. In that case, the tank regulator would drop the pressure between the tank and the house from the very high tank pressure to ~10psi. A regulator at the house would then reduce the pressure again to ~11" WC (~0.4PSI). If that is the case, it is unlikely you have a pressure drop issue between the tank and the house. The second chart in the file shows the capacity at 1PSI drop. A higher pressure drop due to higher demand would not likely be an issue unless the pressure dropped below the rating of the regulator.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    rbphhc
  • rbphhc
    rbphhc Member Posts: 126
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    I just measured the main trunk line *inside* the house. It is 5/8" OD. The outside line is definitely a notch smaller (I will attach a photo), which means it is 1/2" OD.

    Which means, according to the chart, we have a rough *maximum* energy delivery to the house of 225k BTUs (175' first stage to second). Which means we're kind of screwed.

    Because we basically need ALL that just to run the tankless properly (luckily we haven't bought it yet). I'd hate to downsize it too much.

    Question: is it possible to adjust pressure at the first stage regulator? I'm guessing even 12psi would give us a helluva lot more BTUs than 10psi. Or is the only option to upsize the line from the tank to the house? Because that's never gonna happen.

    I'm starting to understand why they chose 2 40gal HWTs to run everything here. It's all they had left for BTUs, once the other appliances were accounted for.

    Note: the current system has had no problem running 2 40 gal HWTs, a 6-burner stove, a RInnai wall blower, a gas dryer, and a gas fireplace, all simultaneously. But a HWT is only 35k. A modern tankless HWH is @ 200k.

    Do I really need to rethink this entire system? Here's my list:
    dryer 35k
    stove 65k
    wall heater 30k
    fireplace 20k

    That's already 160k. Which means, if 225k total is true, we only have 65k to make DHW plus a little in-floor hydronic. Is it back to the drawing board??
  • rbphhc
    rbphhc Member Posts: 126
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    Looks like adjustable first-stage regulators are common, and go up to 12 psi. Assuming that would deliver significantly more BTUs/hr to the 2nd stage regulator. Anyone got a chart? Googling...
  • Mad Dog_2
    Mad Dog_2 Member Posts: 7,245
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     Butane has the highest BTU valve of all flammable games, I believe. MD
    rbphhc
  • rbphhc
    rbphhc Member Posts: 126
    edited February 2023
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    Photos. First stage top of tank; From the tank up to the house; At the house.




  • Jamie Hall
    Jamie Hall Member Posts: 23,649
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    To go back to the basic physics here... the pressure loss in a pipe is proportional to the length of the pipe -- naturally -- and the SQUARE of the velocity of flow. The volume of gas is proportional to the area of the pipe and the velocity of flow. Now there is no arbitrary upper limit on either velocity or, therefore, head loss -- if you can tolerate the head loss. There is, however, a decided practical limit: it you have two regulators in series, as you do, there is a limit to the highest stable pressure the upstream one can put out -- and there is a limit to the lowest pressure the downstream one can tolerate and still produce a regulated final pressure.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    rbphhc
  • rbphhc
    rbphhc Member Posts: 126
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    To go back to the basic physics here... the pressure loss in a pipe is proportional to the length of the pipe -- naturally -- and the SQUARE of the velocity of flow. The volume of gas is proportional to the area of the pipe and the velocity of flow. Now there is no arbitrary upper limit on either velocity or, therefore, head loss -- if you can tolerate the head loss. There is, however, a decided practical limit: it you have two regulators in series, as you do, there is a limit to the highest stable pressure the upstream one can put out -- and there is a limit to the lowest pressure the downstream one can tolerate and still produce a regulated final pressure.

    OK, but what ARE those limits, and can this setup be tweaked to feed a 199k monster? Or do I have to downsize the tankless? Or is my headroom so limited I have to redesign the entire system, and go back to (god forbid) tank(s)??
  • hot_rod
    hot_rod Member Posts: 22,476
    edited February 2023
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    What is your total load, add up all the appliances, then do the tube sizing.

    There is some wiggle room between copper L and ACR copper

    1/2” copper L gets you closer to 400k at that length. It would be an actual 5/8 od however, so get an accurate measurement or look for the stamping on the tubing

    so you need two pieces of stable data, combined load and actual line size from tank to 2 nd stage

    or stage how you run the appliances. It’s rare to run every burner and the oven at once, so calculate how the loads could be managed with what you have.

    id check with a certified trained knowledgeable Lp person before you start tweaking regulators.
    your last guy isn’t one of them🤓

    Do you own the tank and regulators or are they the suppliers?

    we had to recertify our LP installers license every 2 years and test on all the sizing math every time, as well as safety protocol 
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    rbphhc
  • Zman
    Zman Member Posts: 7,605
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    I would not worry about the first stage, even if you have a drop of 3 psi you will still have good pressure at the second stage. Your issues will be from the second stage onward if you have issues.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    rbphhcLarry WeingartenMad Dog_2SuperTech
  • rbphhc
    rbphhc Member Posts: 126
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    hot_rod said:

    What is your total load, add up all the appliances, then do the tube sizing.


    I did, above.
    "Here's my list:
    dryer 35k
    stove 65k
    wall heater 30k
    fireplace 20k
    That's already 160k. Which means, if 225k total is true, we only have 65k to make DHW plus a little in-floor hydronic."



    There is some wiggle room between copper L and ACR copper

    1/2” copper L gets you closer to 400k at that length. It would be an actual 5/8 od however, so get an accurate measurement or look for the stamping on the tubing


    Yep, as above, tank-to-house line is 1/2" OD. According to the chart linked above, that's 225k BTUs delivered, at @ 175' distance.


    or stage how you run the appliances. It’s rare to run every burner and the oven at once, so calculate how the loads could be managed with what you have.


    Yep. But hard to predict when the tankless is going to kick on, and that'll suck most of the BTUs up.


    id check with a certified trained knowledgeable Lp person before you start tweaking regulators.
    your last guy isn’t one of them🤓


    Yeah, but he's the 'professional. :/


    Do you own the tank and regulators or are they the suppliers?


    I believe they are supplier-owned. I am property manager, not owner.



  • Mad Dog_2
    Mad Dog_2 Member Posts: 7,245
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    Great advice for you.  Maf dog
  • yellowdog
    yellowdog Member Posts: 159
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    get a new propane supplier. the tech has no clue how to size propane lines. you are borderline undersized for what you currently have connected. you will need to run 3/4 black iron from the regulator into the house to the new rinnai and pick up all of the other takeoffs. 5/8 copper can only handle 206k btu at 10 feet. you will need to repipe a lot of the piping in the house to add the new rinnai.
    rbphhcCLamb
  • rbphhc
    rbphhc Member Posts: 126
    edited February 2023
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    yellowdog said:

    get a new propane supplier. the tech has no clue how to size propane lines. you are borderline undersized for what you currently have connected. you will need to run 3/4 black iron from the regulator into the house to the new rinnai and pick up all of the other takeoffs. 5/8 copper can only handle 206k btu at 10 feet. you will need to repipe a lot of the piping in the house to add the new rinnai.

    Thank you. That's what I thought (and said to the guy).
    BUT.
    What about the 170 ft of 1/2" OD from the tank to the house?
    According to charts, that limits us to 225K BTU for the whole system, no matter what we run inside.
    Can we tweak the 1st stage reg to get 12psi? How much would that gain us? I have not been able to find that # online.
  • rbphhc
    rbphhc Member Posts: 126
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    OK. Phew. Just spoke to a supervisor at the propane company, who confirmed that we need 3/4" black pipe off the regulator at the house, and also need to upgrade to 3/4" from the tank to the house. Mo money, obviously, but at least a safe, properly sized system. Ecch. Onward! Thanks for the feedback!
    yellowdog
  • rbphhc
    rbphhc Member Posts: 126
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    BTW, he also said that it's illegal to tweak the 1st stage regulator. You can only run 10psi max to the house in a residential system. FTR.
  • hot_rod
    hot_rod Member Posts: 22,476
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    I agree that all the piping inside and out is undersized for the loads you plan on running.

    Come spring or summer it is fairly easy to rip in a new poly line from the tank. The piping inside may not be as easy if it isn’t exposed.

    Some first stage regs are adjustable, some are fixed, but that is only 1/2 the problem.

    Change the stove to electric, consider a smaller tankless😏
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    rbphhc
  • GroundUp
    GroundUp Member Posts: 1,956
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    I may have overlooked something, but 1/2" at 10 psi from your first to second stage (tank to house) with a 3 psi drop is good for 750k. There is absolutely no reason to upsize the underground portion. I didn't see it mentioned so I'll say this as well- smaller diameter absolutely does not raise the pressure, but a higher pressure in a smaller line allows more BTU capacity than a lower pressure in that same line. Your existing draw is already maxed out for 11" pressure through 5/8" OD copper, and even upsizing to 3/4" iron will not get you where you need to be without going to a higher pressure from the 2nd stage reg. 1" will do it, but not 3/4". Sounds like there are a lot of weird numbers being thrown around by people who don't understand their jobs.
    rbphhcZmanSolid_Fuel_Man
  • rbphhc
    rbphhc Member Posts: 126
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    GroundUp said:

    I may have overlooked something, but 1/2" at 10 psi from your first to second stage (tank to house) with a 3 psi drop is good for 750k. There is absolutely no reason to upsize the underground portion. I didn't see it mentioned so I'll say this as well- smaller diameter absolutely does not raise the pressure, but a higher pressure in a smaller line allows more BTU capacity than a lower pressure in that same line. Your existing draw is already maxed out for 11" pressure through 5/8" OD copper, and even upsizing to 3/4" iron will not get you where you need to be without going to a higher pressure from the 2nd stage reg. 1" will do it, but not 3/4". Sounds like there are a lot of weird numbers being thrown around by people who don't understand their jobs.

    Tank to house is 1/2" OD copper. Chart I consulted said 225k over 175'. 750k would be very good news. Can you confirm this? Thx!

  • rbphhc
    rbphhc Member Posts: 126
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    hot_rod said:

    I agree that all the piping inside and out is undersized for the loads you plan on running.

    Come spring or summer it is fairly easy to rip in a new poly line from the tank. The piping inside may not be as easy if it isn’t exposed.

    Some first stage regs are adjustable, some are fixed, but that is only 1/2 the problem.

    Change the stove to electric, consider a smaller tankless😏


    Piping inside is a nightmare (crawlspace on wet ledge), but it only has to be done once.

    Trying to avoid electric b/c rates are outrageous, and outages are common in rural VT.

    New 3/4 poly to tank was reasonable by supplier, and they can do it in a couple weeks.

    Once new lines are in, system can handle anything we throw at it. Owner wants to double-down on propane (off-grid type).

    Thx!
  • hot_rod
    hot_rod Member Posts: 22,476
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    You’re wise to think of future needs in all of this.
    notice the pressure drop charts for that first stage piping all show 1 psi drop. The second stage reg needs close to 10 psi inlet to regulate properly to 11”. The more you try to flow thru that 1/2” the more the pressure will drop. A gauge at that second stage would determine the actual pressure the the second stage is seeing at your largest load condition.
    plenty of info about that requirement if you dig in at the regulator manufacturers tech info site.

    Negative pressure gas valves found on many tankless need a fairly tight incoming pressure, so that second stage reg needs to be accurate, as does the piping size feeding them

    Copper is $$ If 1/2” could adequately handle those large loads at that distance, Lp installer certainly would not use $$ 3/4”
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    rbphhc
  • rbphhc
    rbphhc Member Posts: 126
    edited February 2023
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    hot_rod said:

    You’re wise to think of future needs in all of this.
    notice the pressure drop charts for that first stage piping all show 1 psi drop. The second stage reg needs close to 10 psi inlet to regulate properly to 11”. The more you try to flow thru that 1/2” the more the pressure will drop. A gauge at that second stage would determine the actual pressure the the second stage is seeing at your largest load condition.
    plenty of info about that requirement if you dig in at the regulator manufacturers tech info site.

    Negative pressure gas valves found on many tankless need a fairly tight incoming pressure, so that second stage reg needs to be accurate, as does the piping size feeding them

    Copper is $$ If 1/2” could adequately handle those large loads at that distance, Lp installer certainly would not use $$ 3/4”

    Thanks Rod!

    Propane co is going to put in 3/4" plastic to the tank. I will also request a pressure gauge at the 2nd stage reg. That way we can make sure we are getting good pressure at the tankless.

    (Question: would it be better/easier to put propane pressure gauge at the tankless itself? Does a tankless generally have some mechanism for regulating pressure internally? Seems a little unwise for manufacturers to count on conditions they can't control.)

    Definitely not putting in 170' of copper. And definitely 3/4 black iron shortest possible run to the tankless. But it's not a problem to branch off from there to existing soft copper lines, is it?

    Would it make sense to reduce to 1/2" black pipe after the tankless to feed smaller loads? Or better to keep 3/4 to other downstream appliances? They are smaller loads - 35k dryer, 20k fireplace.

    Thx again!
  • rbphhc
    rbphhc Member Posts: 126
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    GroundUp said:

    Your existing draw is already maxed out for 11" pressure through 5/8" OD copper, and even upsizing to 3/4" iron will not get you where you need to be without going to a higher pressure from the 2nd stage reg. 1" will do it, but not 3/4".

    Thanks again, GroundUp. So you are saying keep 1/2" OD from tank to house @ 170'. BUT. Switch to 1" off the 2nd stage reg to admit adequate pressure into the system to feed tankless + all other loads. Correct?

    Qs: would we need to maintain that 1" all the way to the tankless? Or just 1" trunk, with 3/4" branch to the tankless?

    Maintain 3/4 to smaller loads, or step down to 1/2"? Any reason not to use existing copper piping after the tankless?

  • GroundUp
    GroundUp Member Posts: 1,956
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    rbphhc said:

    GroundUp said:

    Your existing draw is already maxed out for 11" pressure through 5/8" OD copper, and even upsizing to 3/4" iron will not get you where you need to be without going to a higher pressure from the 2nd stage reg. 1" will do it, but not 3/4".

    Thanks again, GroundUp. So you are saying keep 1/2" OD from tank to house @ 170'. BUT. Switch to 1" off the 2nd stage reg to admit adequate pressure into the system to feed tankless + all other loads. Correct?

    Qs: would we need to maintain that 1" all the way to the tankless? Or just 1" trunk, with 3/4" branch to the tankless?

    Maintain 3/4 to smaller loads, or step down to 1/2"? Any reason not to use existing copper piping after the tankless?

    As stated earlier, the BTUs that a given line can carry is dependent upon pressure. 170ft at 2psi, yes 225k is about it. However your first stage reg should be at 10 psi, which would carry 750k through that same 1/2" line due to the higher pressure. The 2nd stage reg may need to be replaced altogether, and 1" should be run at least to the manifold location before loads start pulling from it. From that 1" manifold/trunk, each load could use its existing line and the new 199k tankless should be able to survive with a 1/2" ID line at only 12 feet of length but gas is one application where bigger is better so 3/4" would be cheap insurance if the threader is already out.
    rbphhc
  • rbphhc
    rbphhc Member Posts: 126
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    GroundUp said:


    As stated earlier, the BTUs that a given line can carry is dependent upon pressure. 170ft at 2psi, yes 225k is about it. However your first stage reg should be at 10 psi, which would carry 750k through that same 1/2" line due to the higher pressure. The 2nd stage reg may need to be replaced altogether, and 1" should be run at least to the manifold location before loads start pulling from it. From that 1" manifold/trunk, each load could use its existing line and the new 199k tankless should be able to survive with a 1/2" ID line at only 12 feet of length but gas is one application where bigger is better so 3/4" would be cheap insurance if the threader is already out.

    Thanks again. Yeah, the 'manifold' wouldn't be much, in this case. Just about 3 ft of 1" pipe into the building, with a tee going 3/4" in one direction (tankless) and 1/2" in the other (stove and wall heater).

    I'm guessing OK to run 1/2" post-tankless to feed the dryer and fireplace? Both smaller loads at 35k and 20k.
  • yellowdog
    yellowdog Member Posts: 159
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    @GroundUp you are mistaken on the 1/2" to the house from the tank. you are looking at the ips chart to get over 700k. in the rego book, 1/2" copper at 10# is only good for 269k at 175'.
    @rbphhc can you make a sketch of your interior piping with sizes and lengths and loads and we can tell you what they will need to do for interior piping.
    rbphhc
  • rbphhc
    rbphhc Member Posts: 126
    edited February 2023
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    GroundUp said:

    The chart I saw said 225k at 10psi. The LP supplier and multiple pros here also seemed to concur with that figure. But I agree, it does seem like a severe drop from 1.2M to 225k. I'm glad if that's wrong, but can you provide any link to confirm that figure I can show to the property owner?


  • hot_rod
    hot_rod Member Posts: 22,476
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    Generally LP suppliers are more than happy to help you use more of their product. Including upsizing lines.
    Just do a sketch of the piping inside, loads, distances. The charts attached a few posts above will give you the required pipe sizes. Much easier to get it right if you are at the site with tape measure in hand.


    All regulators have test ports for checking and maintaining them. You don’t usually see exposed gauges on regulators mounted outside the building. Same for the appliances, they have test ports also. Most high efficiency equipment will lock out at a low gas pressure condition. An error on the screen would indicate the fault of a lockout.

    There are sizing charts all over online, including code books, NFPA, all the regulator manufacturers.

    Included this one to show the difference in different types of copper tube, quite a difference in capacity from ACR to L copper.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    rbphhc
  • rbphhc
    rbphhc Member Posts: 126
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    yellowdog said:


    @rbphhc can you make a sketch of your interior piping with sizes and lengths and loads and we can tell you what they will need to do for interior piping.

    Will do. Stand by.
  • rbphhc
    rbphhc Member Posts: 126
    edited February 2023
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    I forgot to include loads, here's what I think they are:
    Stove @ 65k
    Wall heater @ 35k
    Tankless @ 199k
    Dryer @ 35k
    Fireplace @ 20k

    Proposed new routing:
    - tank to house 170' @ 3/4" poly
    - 2nd stage into house @ 3' x 1" black iron w/ (2) 90s + tee (1 x 3/4 x 1/2)
    - 1/2 tee goes to existing 1/2 ACR feeding stove, then wall heater
    - 3/4 tee goes to tankless (14' @ 3/4 black pipe), then to exitsing 5/8 ACR w/ 3/8 branches to dryer and fireplace.



  • rbphhc
    rbphhc Member Posts: 126
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    Question: with new 3/4 supply from tank to house and new 2nd stage reg w/ 3/4 NPT out, could we get away with 3/4" trunk into house, maintaining 3/4" to tankless? Propane supplier seemed reticent to put in 1" for some reason.
  • GroundUp
    GroundUp Member Posts: 1,956
    edited February 2023
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    yellowdog said:

    @GroundUp you are mistaken on the 1/2" to the house from the tank. you are looking at the ips chart to get over 700k. in the rego book, 1/2" copper at 10# is only good for 269k at 175'.
    @rbphhc can you make a sketch of your interior piping with sizes and lengths and loads and we can tell you what they will need to do for interior piping.

    Actually you are mistaken, because you're only looking at the 1 PSI pressure drop chart. The drop here is over 9.5 PSI. My 750k figure was actually quite conservative.
    rbphhcSolid_Fuel_Man
  • rbphhc
    rbphhc Member Posts: 126
    edited February 2023
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    GroundUp said:


    Actually you are mistaken, because you're only looking at the 1 PSI pressure drop chart. The drop here is over 9.5 PSI. My 750k figure was actually quite conservative.

    OK. According to this chart, looks like 1/2" OD at 10psi over 200' w/ 1psi drop gives us between 250k and 260k at the house.

    GroundUp may have been looking at an "SDR" piping chart. Which, if I'm reading correctly, 1/2" pipe is close to 3/4" INSIDE DIAMETER, at 0.72". The pipe we have is 1/2" OD, which is closer to 3/8" ID. Which is VERY different.

    So maybe both are 'right?' But what matters is the ID of the supply line, not its nominal 'size.' Which in MY case is closer to 0.400".

    So yeah, we are SOL. Even at 150' it's still barely 300k to the house.

    Alas.




  • hot_rod
    hot_rod Member Posts: 22,476
    Options
    Same question for the copper tube inside, is it ACR or plumbing sized, type M or L?

    This table for copper tube covers everything inside at 11". Both coppers are listed, and again the plumbing size tube, type L column carries more.

    A rule of thumb BTU table for appliances, although the instantaneous estimates are high, use your actual number there.
    These are the most commonly used sizing tables NFPA, same ones you find in code books
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    rbphhc