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Tubing size, spacing, flow rate for a joist install

Geode Member Posts: 20
Hello group,

I had been working with NRT radiant to design my radiant system. At the time I was planning on installing radiant in a basement slab, but was not sure If I wanted to do the first floor as well.

I asked NRT to do a heat load calculation for my first floor as well (19kbtu). Additionally NRT confirmed that my HX and injection pump could handle the addition of the first floor heating zone. NRT indicated it would be fairly straight forward to add the first floor zone.

Sadly NRT is no more, and as I continue to review the documents they provided me I wish I had them design the first floor as well. Working with NRT was a pleasure, I hope they are doing well.

I'm not exactly sure how to proceed, but I think the first step would be to choose the first floor tubing, spacing flow rate etc based of the 19kbtu heat load calcs?

Thanks for any thoughts/advice etc



  • Zman
    Zman Member Posts: 7,467
    edited July 2014

    You will want to determine the required BTU output per square foot in each room.You will also need to know the design water temp your system is running the coldest design day.

    If you use 1/2" tubing and keep the lengths around 200', you should be able to acheive your design flow rate fairly easily.

    Some sort of aluminum track will be needed. Here is some good info from uponer.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Geode
    Geode Member Posts: 20
    Tubing spacing

    27 btu's per square foot.

    The plan at the moment is to have just one zone for this floor (It's 705 sq. ft. total).

    The floor joists are 16" o.c.

    This is from NRT:

    Until the rest of the system is determined the max system water temps are at 105. Once the distribution of the first floor is set this may raise the water


    Thanks for the help, and the link to the aluminum track. I'll look it over later today.
  • Rich_49
    Rich_49 Member Posts: 2,738

    Rob Brown is at Rockport Mechanical in Lewiston Me .  Maybe you could contact him for assistance
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • Zman
    Zman Member Posts: 7,467

    It looks like you may need to raise your temps into the 120-130 range.

    Not a big deal. Keep the loops short ans you should be fine.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein