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Radiant Heat custom manifold with spaced out T

DrVit Member Posts: 17
Question to pro radiant heat installers - would system work if instead of doing home runs for loops to one location manifold, I will use a 20' of 3/4" copper on one end of the wall for supply, another 3/4" on another side of the wall for return, cut T's for each section of 200-250' of loops, and use valves on each run for adjusting water flow?


  • billtheplmbr3845
    billtheplmbr3845 Member Posts: 41
    Yes, but do a reverse return. First supplied last return. Also depending on the amount off loops being connected, make sure you can get enough g.p.m and btu's thru 3/4", you may have to change the mains accordingly
  • ch4man
    ch4man Member Posts: 296
    remote manifolds are done all the time.
  • GroundUp
    GroundUp Member Posts: 1,868

    Yes, but do a reverse return. First supplied last return. Also depending on the amount off loops being connected, make sure you can get enough g.p.m and btu's thru 3/4", you may have to change the mains accordingly

    In most cases, reverse return kind of defeats the purpose of what I think he's trying to do. I should already have an answer to this but I don't so I'll ask you; why?

    I've got an underfloor system done in the manner the OP is describing, in a direct return fashion. It took some time to get balanced, but works perfectly since. When reverse return is not an option, we go to plan B right?
  • DrVit
    DrVit Member Posts: 17
    Attached is the design I've had in mind. I'm assuming reversed returns are for balancing out water flow? I was thinking about having valves on each loop so I can balance out flow if that's a case.

    Also, radiant I'm doing is purposed just to have warm floor for a comfort. I have existing baseboard heat to supplement BTU if radiant will not be sufficient. Based on layout of the open space in basement - I'm planning to do 5 loops totaling about 1200' of 1/2" Pex. Was planning to use 1 mixing valve, 1 pump, 3/4" headers, and just one Tstat. Do adjustments mostly with valves on loops if needed. Hope this idea is workable.
  • hot_rod
    hot_rod Member Posts: 21,868
    Here is another piping and mixing that would allow outdoor reset on the high and low temperature zones, plus boiler return protection with proper mixing device.

    Pipe it this way and ODR could be added later.

    Your drawing for the radiant is correct, first loop supplied is last returned.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Zman
    Zman Member Posts: 7,546
    That type of header arrangement will work just fine with balancing valves or reverse return.
    1000 sq/ft at 8" centers will take more than 3 loops, probably 5 loops at 250'-300'.
    Be sure the mixing valve is designed for radiant,
    I don't understand the near boiler piping.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Gordy
    Gordy Member Posts: 9,546
    Looks like near boiler piping is doing the high temp baseboard, and the radiant is taking off of that with mixing valve.

    How will this be controlled? One or the other? Both together? Or radiant with baseboard as supplemental when temps drop?

    If I understand correctly you want to run both together?
  • DrVit
    DrVit Member Posts: 17
    Thank you guys for your inputs !
    Near boiler diagram is just a schematic to show existing heating. Which is 1" supply line branching out as it goes, and separate returns with zones valves. I have attached a photo of the space on the wall where I was thinking of connecting mix valve and pump. With cutting into 1" pipe to get hot and using one of the existing stub outs on return. There is no primary/secondary, no outdoor temp controls - just basic boiler install.

    - was thinking about coming from mix valve with 3/4 copper, T-out for first 2 loops in one direction ~ 250-280', then supply 3/4" to another spot for 2 loops (they will be under floor with transfer plates), and 1 last loop ~ 180' will be above floor in bathroom with transfer plates under tile (sleepers, transfer plates, durok, tile).

    - system will be used along side with existing baseboard heat. Purpose is to add a comfort of warm floor to walk barefoot. So what ever heat loss needs to be supplemented - existing baseboard will be a backup.

    I'm figuring 3/4" copper for supply would be sufficient?
    Also I was thinking just using 1 mixing valve and 1 pump, and put everything on 1 T-stat. Do adjustments with valves on loops.

    Also, any suggestions for possibly prefab 2 ports 3/4" x 1/2" pex valves? Not sure if I should just custom build, or buy some prefab copper-to-pex valves.

    Also if I need to add some kind of flow meters, gauges, etc on each loop for "scientific" adjustments, or just use basic valves and adjust based on comfort level.

    P.S. Side question - is there a way in this forum to get notified when someone is posting a comment? Like email notification?

    Thanks for all of your help !
  • DrVit
    DrVit Member Posts: 17
    Also - as far as T-stat - what kind of solution would you recommend?
    - floor censors or wall T-stat?
    - any particular brand? My brother (its his house I'm helping him with) likes Nest T-stat. I doubt they have floor sensor, unless it can be wired in somehow
    - put say outdoor sensor and turn on when winter is here and off when summer comes? And just adjust flow so floor is not too hot?
  • Gordy
    Gordy Member Posts: 9,546
    edited January 2019
    You'll have to rethink a new SWT to the baseboard. Possibly the same as floors. Otherwise the baseboard will satisfy the tstat before floors warm. All you are doing is adding more emitter to the system which is already able to carry the load I'm assuming. All you want is the neutral floors?

    I'd recommend the floors as the primary emitter, and baseboard as secondary when floors can't carry the load. This way you always benefit from the floors.
  • rick in Alaska
    rick in Alaska Member Posts: 1,452
    Right next to the title of this post, Radiant Heat custom manifold with spaced out T, is a "star". Click on it and it will highlight yellow, and then you will be notified if anyone posts any more comments.