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Gravity Boiler System - add rad

desol
desol Member Posts: 2
in Plumbing

Hi. Does anyone know, can I put two smaller rads off of a single branch line? Right now there's only 1 rad on the branch line, but I think I would like to add another. Thanks

Comments

  • mattmia2
    mattmia2 Member Posts: 10,958

    Is it still gravity? Pictures of the boiler and the mains and what you want to add on to. If it has been converted to forced circulation or if you can add a forced circulation zone you have a few options, if it is still gravity you have to be very careful.

  • desol
    desol Member Posts: 2
    https://forum.heatinghelp.com/discussion/comment/1812865#Comment_1812865

    Hi. No it's still gravity. The whole system seems to work as is…but I want to add one more rad. A small one in the bedroom. I figure if 3/4 inch pipe will feed a bigger rad (which I think it does), why shouldn't it feed two small ones? I've attached a picture of the pipes I want to cut into….put t's and go off to the right to the new small rad upstairs.

    20241003_125855.jpg

  • Big Ed_4
    Big Ed_4 Member Posts: 3,024
    edited October 4

    You first need to figure the installers formula . Hight of riser is positive for gravity , hozontal , fittings and smaller pipe size are a negative or restrictive to gravity…What size riser was used for the first floor and normally the second floor riser pipe would be smaller if they did the math .. Best to follow suit to the original installer ……

    There was an error rendering this rich post.

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,507

    Because gravity system has no circulator the only thing that moves the water is the difference in weight of hot water versus cold water.

    Any alterations you make can disrupt the system. I would have some valves to balance the flow but even the resistance of those valves can upset the flow

    If you brach off with two tees (supply and return) the water will favor going straight though the tee instead of turning the corner

  • delcrossv
    delcrossv Member Posts: 1,357
    edited October 6

    You need a height change and to be aware of viscous drag in the pipe. So for a single rad, maybe 3/4 or 1 inch iron pipe for both supply and return. If there's a delta T the hotter water will rise up the tee.

    I'd recommend against balancing valves and induce balancing with pipe choice.

    We could use more detailed information on how you're planning on making the run. Heights, pipe size, bends,etc.

    Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.
  • mattmia2
    mattmia2 Member Posts: 10,958

    An orifice plate in the emitter that is heating might be the way to balance the new parallel emitters

    delcrossv
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,217

    ………and some radiators can't be used on gravity systems. Too much resistance from small pathways.

    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab

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