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Question on pex in ceiling heating.

cnmdesign
cnmdesign Member Posts: 101


Hi to all

Gutted my house April of 20 and now I'm to the point where the first floor ceiling (1,500 sq/ft) has been covered with OSB and is ready to receive the foam board spacers for the Pex-Al-Pex.

It's a 3k sq/ft project and I hope to have half done by the end of September. Working on my330 sq/ft. 22x15 kitchen (running pex long ways using Johns (Over your head https://www.pmmag.com/articles/96488-radiant-ceilings-are-a-great-option-in-many-systems) and I have a few questions:

*** Does the rule on only using up to 300 ft of .5 in. pex-al-pex still apply?

*** Using his layout, how many square feet can you cover (give or take) using 300 of pex?

*** If I need over 300 ft. will the Caleffi TRVs compensate for the difference somehow?

*** Is there any major changes to his ceiling heat idea before I get too far down the road?

Hope everyone had a nice 4th.

Robert
Combat Veteran owned, Final Salute LLC on FaceBook & Twitter.
www.afinalsalute.com

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 16,062
    The 300 foot rule of thumb -- and it is that, not a hard number -- is there for two reasons. First, to maintain a reasonable pressure drop through the loop. Second to maintain a reasonable temperature difference between the beginning and the end.

    It is much ore satisfactory to use two shorter loops rather than one longer loop.

    As to how many square feet? Well... if your tubing spacing is one foot, 300 square feet. 6 inches? 150 square feet. And so on.

    If you need over 300 feet, break it into two loops. The Caleffi TRVs are wonderful gadgets, but they don't repeal the laws of physics.

    Done right, ceiling heat is very good. Do I personally like it? No -- I like the air temperature to be warm, and I hate having my legs and feet cold when I'm sitting at a table. But that's me. It is less expensive -- and a good deal easier to do -- than in-floor radiant in a retrofit, and those are the main advantages.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    cnmdesignDerheatmeister
  • Derheatmeister
    Derheatmeister Member Posts: 1,081

    The 300 foot rule of thumb -- and it is that, not a hard number -- is there for two reasons. First, to maintain a reasonable pressure drop through the loop. Second to maintain a reasonable temperature difference between the beginning and the end.

    It is much ore satisfactory to use two shorter loops rather than one longer loop.

    As to how many square feet? Well... if your tubing spacing is one foot, 300 square feet. 6 inches? 150 square feet. And so on.

    If you need over 300 feet, break it into two loops. The Caleffi TRVs are wonderful gadgets, but they don't repeal the laws of physics.

    Done right, ceiling heat is very good. Do I personally like it? No -- I like the air temperature to be warm, and I hate having my legs and feet cold when I'm sitting at a table. But that's me. It is less expensive -- and a good deal easier to do -- than in-floor radiant in a retrofit, and those are the main advantages.


    Jamie... i agree and disagree with you
    i agree with the cold legs and feet comment but disagree with the easier to install radiant ceiling and less expensive comment..We have designed and installed both radiant retro ceilings and retro infloor systems ..... Radiant Ceilings are far more labor intensive and therefore come with a higher installed cost.
    Paul Pollets
  • cnmdesign
    cnmdesign Member Posts: 101
    edited July 14
    Answered
    Combat Veteran owned, Final Salute LLC on FaceBook & Twitter.
    www.afinalsalute.com
  • JUGHNE
    JUGHNE Member Posts: 8,425
    I agree with Jamie about the cold legs and feet.
    If you were to have a breakfast nook in a corner or even against a wall, I would install wall radiant in that area. Just up 3-4' away from picture hanging height.

    As for the large dining room table, for Thanksgiving and such, sitting in the middle of the room, I would guess there would be enough body heat in the room to not feel a chill under the table.

    But the daily coffee/brunch nook would benefit from wall heat heat IMO.
    Also any place you might sit for a while, such as office desk areas and sewing machine stations.
    We have wall heat in our bathroom in addition to floor heat.
    The wall heat is the prime source.
  • cnmdesign
    cnmdesign Member Posts: 101
    edited July 14
    My Ranch home is 30x55. Can I run a 1 inch manifold along the top of the middle support wall in the basement and run each first floor ceiling radiator off of it? This would cut the loop run down to less than 20ft. from ceiling to manifold round trip for each room.
    Combat Veteran owned, Final Salute LLC on FaceBook & Twitter.
    www.afinalsalute.com
  • cnmdesign
    cnmdesign Member Posts: 101
    Does the TRV set the flow rate for the required BTUs for a set temp?
    Combat Veteran owned, Final Salute LLC on FaceBook & Twitter.
    www.afinalsalute.com
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