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Piping size for myson panels

rosy Member Posts: 9
edited September 2019 in Radiant Heating
A mechanical room and control panel are about 12' below grade and three Myson panel radiators (2) 24" x 18" and (1) 32" x 24" ( in three bathrooms, each fed by approximately 20 feet of 1/2 - 02 pex. Supply and return lines for the three radiators will run to a crawlspace and route into a 1" copper manifold with 1/2" balancing valves. The Myson's will have TRV valves.

Myson rates the 24 x 18's at around 3k btus and the 32 x 24 at 4.5k btus.
The question is whether to supply those manifolds with 3/4" supply and return pipes or 1/2"? Pump will be a Grundfos 15/58 3 spd. Seems like 3/4" is the way to go to get enough head to overcome the situation of all 3 activating at the same time. The rise from the manifolds in the crawlspace is 2-3 feet.




  • Ironman
    Ironman Member Posts: 6,876
    So, are you saying the total for all three of the 24 x18's is 3k btus or 3k btus for each totaling 9k btus?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • psb75
    psb75 Member Posts: 570
    No. Two at 3 btuh ea. and one at 4.5 btuh for a total of 10.5 btuh.
  • Ironman
    Ironman Member Posts: 6,876
    The height makes no difference in a closed loop.

    You'd need a minimum of 1" copper to feed the manifolds using a standard 20* delta T.

    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Rich_49
    Rich_49 Member Posts: 2,692
    1/2 is fine .
    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
  • psb75
    psb75 Member Posts: 570
    Sorry, I meant 10.5K btuh.
  • TAG
    TAG Member Posts: 622
    FYI -- I have used the Buderus panels w/ bypass on three houses using 1/2 pex. Two houses have third floor ... w/o issue. I think at the time I was told keep it around 12k max BTU per zone w/ 1/2 inch.

    These are old school CI Buderus boilers -- panels are the main loop using outdoor reset .. small brute primary pump. All the panels have the Danfoss thermostats.

    It's really a great system if you can lay out the panels properly