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Size of pipes in forced water heating system

Bill de Rosa
Bill de Rosa Member Posts: 3
Thank you again. I find your replies very helpful.
As you have been so kind I would like to take further advantage of it.

What are the balance considerations which come into play?? Also is there a place, like the one you gave me for the gravity system, where I can learn the basics of a forced water system?? I have quite a few questions that come to mind, such as circulator type and size, kind of pipe material (i.e. iron vs copper) and so on.

For what professionals are concerned, I am quite discouraged, that is the reason I am attempting to learn as much as I can. It seems that everybody is interested in changing the boiler, but nobody wants to mess with the plumbing. I have had three H/C companies look at the system; they all gave me different answers, nobody even mentioned what, after following your suggestion and reading about the gravity system, seems a quite obvious thing: I have a system converted from "gravity" to "forced". I apologize for venting my frustration, but I was trying to explain why I am attempting to learn as much as I possibly can.

Than you again.

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Comments

  • Bill de Rosa
    Bill de Rosa Member Posts: 3
    Pipe sizes in forced water hydronic system

    I need some help!! I am refinishing the basement in an old brick building with forced water heating system. The building is two floors high on top of a good height basement. The pipes (cast iron) carrying the water from the boiler start at 3/4 at the boiler and increase to 3 to 4 inches along the basement ceiling, before being reduced again to 3/4 as they start rising toward the first and second floor. The return pipes enter the basement at 3/4 and expand to 3 4 inches along the ceiling before being reduced to 3/4 at the boiler return manifold. What is the function (if any) of such large pipes?? I would like to change them with 1" pipes so I can gain some head space. If I do that will there be enough heat still carried to the first and second floor??

    Thank you in advance for your ideas.
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,636
    Sound like

    you have an old gravity hot water system. You can read all about it here (cut and paste)

    http://www.heatinghelp.com/heating_howcome1.cfm
    Retired and loving it.
  • Bill de Rosa
    Bill de Rosa Member Posts: 3


    Thank you for your reply. I have followed your suggestion and read about the gravity system. It gives suggestions on how to replace near-boiler pipes.

    My question is: can I change all the pipes running along the basement ceiling using the same formulas without interfering with (and eventually improving) the heating efficiency of the system??

    Thank you
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,636
    Those rule

    apply to the near-boiler piping. You can reduce the size of your basement pipes if your system has a circulator, but the size would be based on the flow rate, which is based on the heat loss. One-inch pipe, for instance, has a maximum flow rate of 8 gallons per minute. Based on a 20-degree temperature drop across the system, that represents 80,000 BTUs per hour, which is quite a bit.

    If you're not comfortable with the sizing, it would be best to have a pro look it over and make recommendations. There's also the issue of system balance to consider.

    Thanks for the good question.
    Retired and loving it.
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