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Pipe size vs double header

Snowmelt
Snowmelt Member Posts: 1,422
edited September 2020 in THE MAIN WALL
On your riser going into your header vs using both risers.........
For sake of arguments a smaller residential of 100,000 btu
I know that you guys are going to say use both headers all the time and increase pipe size.
But what would be better if you just increased pipe size and use one header or keep minimum recommended size and use 2 risers & why?
Follow up question goes it matter how many risers are on original main?

Comments

  • SlamDunk
    SlamDunk Member Posts: 1,639
    edited September 2020
    2" out of the boiler vs 4" out of the boiler. the boiler ports are still 2 inches which means velocity will be faster with only one port. You have a venturi to deal with.

    You get slower, drier steam velocity using both ports -economically.
    STEVEusaPA
  • Snowmelt
    Snowmelt Member Posts: 1,422
    Thanks slam that’s a short and right to the point.
  • ChrisJ
    ChrisJ Member Posts: 16,127
    A single 3" has more surface area than two 2" but two 2" may pull more evenly. This is assuming the boiler has 3" tappings.

    Going up a size out of a tapping is a huge no no in my book because you're dropping velocity and there's no where for water that's already been sucked out to go, meaning it'll tend to get trapped in that riser. The slower steam will tend to not want to pull it up as well as higher velocity.


    Going down a size after you leave the tapping could be beneficial and certainly won't hurt. But never go up a size.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
    STEVEusaPA
  • Snowmelt
    Snowmelt Member Posts: 1,422
    Ok so on the riser you don’t increase the size but you will increase it at the header ?
  • Jamie Hall
    Jamie Hall Member Posts: 24,108
    Snowmelt said:

    Ok so on the riser you don’t increase the size but you will increase it at the header ?

    Just so. Remember that the idea is to let the steam slow down somewhere where the water droplets can drop out and make their way, unimpeded, back to the equalizer and the back to the boiler. If you increase the riser size, they'll drop out in the riser, and try to get back to the boiler that way, which isn't helpful. But if you increase at the header, and the header is piped riser/second riser if any/steam main(s)/equalizer, they'll happily drop out in the header, miss the corner up to the steam main or mains, and go back down the equalizer.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    ChrisJ
  • Snowmelt
    Snowmelt Member Posts: 1,422
    Ok Jamie thanks, so don’t increase risers but increase the header.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,074
    edited September 2020
    I don't agree. I have no problem blowing up the riser size.

    The job of the boiler is to be a steam boiler and keeping the water in the boiler is the deal. It's job isn't to circulate water through the header

    It makes no sense to me to allow the water to blow up into the header and recirculate back to the boiler

    the riser size is supposed to keep water in the boiler and a bigger riser will help make that happen. 2 risers are better than 1 riser blown up. The more time the water is in contact with the steam the more the water will condense some of the steam
  • Snowmelt
    Snowmelt Member Posts: 1,422
    I wish dan would chime in on this .......
  • ChrisJ
    ChrisJ Member Posts: 16,127
    I don't agree. I have no problem blowing up the riser size. The job of the boiler is to be a steam boiler and keeping the water in the boiler is the deal. It's job isn't to circulate water through the header It makes no sense to me to allow the water to blow up into the header and recirculate back to the boiler the riser size is supposed to keep water in the boiler and a bigger riser will help make that happen. 2 risers are better than 1 riser blown up. The more time the water is in contact with the steam the more the water will condense some of the steam

    Im assuming you are misunderstanding what I said.
    I was talking about using a larger size riser than the tappings.  For example a 3" on a boiler that only has 2" tappings.

    So it'll go from 2" to 3" after it's already left the boiler.


    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Danny Scully
    Danny Scully Member Posts: 1,434
    The tapping on the boiler sets the velocity, increasing it after that does not slow it down...so ultimately I’m agreeing with you @ChrisJ, but for a different reason. I just think it’s a waste. 
  • Snowmelt
    Snowmelt Member Posts: 1,422
    Dan would you oversize anywhere in the system?
  • Danny Scully
    Danny Scully Member Posts: 1,434
    @Snowmelt, there is a formula for header sizing that I always use. Many times we upsize the header against the manufacturers specifications. In terms of the entire system, in counterflow situations we will upsize, as well as longer run-out (counterflow) situations.  
  • ChrisJ
    ChrisJ Member Posts: 16,127

    The tapping on the boiler sets the velocity, increasing it after that does not slow it down...so ultimately I’m agreeing with you @ChrisJ, but for a different reason. I just think it’s a waste. 

    You don't feel the velocity drops once it gets to the larger piping? Isn't this how and why venturis work?
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
    ethicalpaul
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,074
    Say a 2" tapping with a 2 1/2" riser. I don't feel the velocity in the 2 1/2" riser will be the same as a 2" riser. The velocity will slow as soon as it passes through the tapping. Plus the tapping is only what? an 1 1/2-2" Its not even going to have time to speed up much
  • Jamie Hall
    Jamie Hall Member Posts: 24,108
    Interesting discussion. Viewpoints on all sides here! Seems to me, though, that the main thing to remember is that where the steam slows down -- and it will if the pipe size is increased -- water droplets will form. Can't avoid it -- it's one of the oddities of saturated steam, even if you don't have some carryover -- and the objective of the exercise is to avoid getting those water droplets into the steam mains, but letting them go somewhere (like the equalizer) where they aren't a problem. Whatever works...

    The advantage, as I see it, to two risers in longer boilers is that it avoids potential problems with tilting waterlines, as well as lower velocities, and therefore less potential for entrainment and carryover. Are they needed? Not always. Cedric -- a 5 section Weil-McClain 80 -- only uses one riser and is fine, but of course it also has a generous dropped header -- and a big steam drum after that. Odd... Boilers with side outlets... from the standpoint of the hydrodynamics of the thing, pipe as generously as possible!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • ChrisJ
    ChrisJ Member Posts: 16,127
    edited September 2020
    Gentlemen,

    The only thing that matters as far as pulling water of a steam boiler is the diameter of the opening of the boiler and it's distance from the water and the amount of steam you're pushing through it.

      It doesn't matter if it's 1 foot thick or 0.0001" thick the velocity is what it is at that spot.

    The gas doesn't need time to accelerate.   When you force X amount through a certain size opening it must go a certain speed.

    Sigh..


    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • ChrisJ
    ChrisJ Member Posts: 16,127
    Here's a video showing how water gets sucked up into the piping of a boiler.

    Yes, it's high pressure and a commerical boiler but the idea is the same

    https://youtu.be/dorhr85ASRM
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
    CLamb
  • unclejohn
    unclejohn Member Posts: 1,833
    I have never installed a steam boiler but it would seem to me that lower velocity would mean less water leaving the boiler.
  • SlamDunk
    SlamDunk Member Posts: 1,639
    @ChrisJ is right on all counts. I would like to believe the boiler manufacturers considered everything before they decided on tapping size and quantity.

    You've got the all important "A" dimiension, steam pressure less than, equalto 2psi and finally installation costs. The larger the pipe, the more expensive the install, not to mention the added difficulty of threading and sizing larger pipe.

    Putting 4" risers on a residential boiler is like putting a V12 in a volvo 240. It is cool, but it is expensive.
    ethicalpaul
  • Snowmelt
    Snowmelt Member Posts: 1,422
    I only did a hand full of boilers, I never had to cut pipe. I did have a lot of nipples that I had to bring to supply house but I do have my standard nipple tray.
    At the end of this conversation I am believing 2 risers are better then one. Bigger is better (2 inch to 2 1/2 or 3) drop header is even better for the steam. And if the header is a even a bigger barrel it will slow down the steam even more.
  • ChrisJ
    ChrisJ Member Posts: 16,127
    edited September 2020
    Required riser size depends on the boiler output.  Just as with boilers and air conditioners bigger isn't always better.

    They should be sized appropriately.  Doing more than a 2" header on an EG30 is a waste in my opinion.

    An EG40-45 a 3" is nice.


    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Snowmelt
    Snowmelt Member Posts: 1,422
    I’d keep that in mine.
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,585
    I would use two risers of the size specified by the boiler manufacturer and the go larger on the header. 
    Retired and loving it.