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Radiant Heat Manifold Questions

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Fluke216
Fluke216 Member Posts: 33
in THE MAIN WALL
I have two 300' loops stubbed up in wall cavity from concrete floor and two 300' loops stubbed down in the same wall cavity from staple up between floor joist for the room above. I think I can use 1 manifold and control these zones separately with actuators and separate thermostats. All loops are 1/2 pex I was planning on running a 3/4 supply and return to a single 4 loop manifold. Any product recommendations or information on if this is correct or not or if it should be done another way would be greatly appreciated Thanks.


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  • Paul Pollets
    Paul Pollets Member Posts: 3,656
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    These loops will have distinct and different SWT, and will need their own manifolds. The slab manifold requires lower temps and the staple-up higher temps. If you supply the staple up with its required SWT, the slab will tend to overheat, even with telestats. The near boiler piping should have a 3 way mix for the slab and a high temp supply for the staple up. Each would have it's own pump, preferably a Smart Delta P pump to accomodate for the telestats.
    EdTheHeaterManFluke216GGross
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,833
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    I was wondering who designed the piping layout and who did the heat loss for the radiant floor rooms? It appears that you have slab piping and staple up piping in 2 different locations. You will need to have separate temperature manifolds for the different types of radiant. Depending on the amount of current or future staple up loops you will have, you may want to send 1" piping to the manifold locations then branch off with 3/4" to the different manifold locations.
    This example was taken from this book http://media.blueridgecompany.com/documents/ZoningMadeEasy.pdf on page 24 and modified to match your situation. The near boiler piping is generic and may not match the manufacturers recommended piping for your boiler. Also if you are using high temperature radiators on this boiler the Staple up zone may also need to have a mixing valve to lower the temperature from that required by the high temperature heat emitters, like Indirect Water Heater or Baseboard type radiators.

    This may be a bit confusing however, if you have questions you can PM me or ask the forum for clarification.

    I hope this helps.

    Mr. Ed
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
    Fluke216
  • hot_rod
    hot_rod Member Posts: 22,131
    edited August 2022
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    good for you installing 3 plates per bay! Also lifting the bar in the slab 👌

    Do you know what supply is needed for the plates. If the load is low you may be close enough to the radiant since you have a wide spacing there. If they are within 15 degrees if one another a single temperature may suffice. Carpet on the slab would bring the temperatures closer together😉

    Or get a manifold that has the pump and mix valve built into it for the slab zones, Caleffi and others offer them
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    EdTheHeaterManFluke216GGross
  • Fluke216
    Fluke216 Member Posts: 33
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    Paul Pollets said:

    These loops will have distinct and different SWT, and will need their own manifolds. The slab manifold requires lower temps and the staple-up higher temps. If you supply the staple up with its required SWT, the slab will tend to overheat, even with telestats. The near boiler piping should have a 3 way mix for the slab and a high temp supply for the staple up. Each would have it's own pump, preferably a Smart Delta P pump to accomodate for the telestats.

    OK makes sense thank you for that info and recommendation. Any other recommendations on manifold types or anything else would be appreciated if not no problem thanks again.



  • Fluke216
    Fluke216 Member Posts: 33
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    EdTheHeaterMan said:

    I was wondering who designed the piping layout and who did the heat loss for the radiant floor rooms? It appears that you have slab piping and staple up piping in 2 different locations. You will need to have separate temperature manifolds for the different types of radiant. Depending on the amount of current or future staple up loops you will have, you may want to send 1" piping to the manifold locations then branch off with 3/4" to the different manifold locations.
    This example was taken from this book http://media.blueridgecompany.com/documents/ZoningMadeEasy.pdf on page 24 and modified to match your situation. The near boiler piping is generic and may not match the manufacturers recommended piping for your boiler. Also if you are using high temperature radiators on this boiler the Staple up zone may also need to have a mixing valve to lower the temperature from that required by the high temperature heat emitters, like Indirect Water Heater or Baseboard type radiators.

    This may be a bit confusing however, if you have questions you can PM me or ask the forum for clarification.

    I hope this helps.

    Mr. Ed

    Ok so the situation was this portion of the house I bought had an addition with no concrete floor. its a walk out basement with room above and small loft above that. I went over some stuff with some companies about the calculation ill have to dig that paperwork up as I this was last year when I did this. I dug down roughed plumbing in removed dirt added stone then 2 in xps and 2 in xps tapered on the edges. I changed the spacing to about 9 inch centers in he slab and its closer together in the bathroom about 6 inches. I figured while I have everything torn out there's a room above minds well add the pex in-between the floor joists to heat the room above. Again I think I went over a little with radiantec about some things. These
    studs are 24 in centers so I ran 3 down each bay. I don't have a better picture because I put up a foil barrier but the aluminum plates cover almost all the tubing except for the radiuses at the end. There should be nothing else in that area for radiant as its on the end of the house I could add staple up loops in my basement but that would be in the same room as the boiler. So maybe 3/4 would suffice let me know what you think. Is there advantage disadvantage to copper vs pex as the supplies? I assume the should be insulated also. I don't have a boiler picked out at the moment was thinking an on demand propane for this situation. sorry for all the questions the drawing makes sense and I greatly appreciate you taking the time to respond and modify that to give me a good example.
  • Fluke216
    Fluke216 Member Posts: 33
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    hot_rod said:

    good for you installing 3 plates per bay! Also lifting the bar in the slab 👌

    Do you know what supply is needed for the plates. If the load is low you may be close enough to the radiant since you have a wide spacing there. If they are within 15 degrees if one another a single temperature may suffice. Carpet on the slab would bring the temperatures closer together😉

    Or get a manifold that has the pump and mix valve built into it for the slab zones, Caleffi and others offer them

    Thank you, all the stuff I went over showed a 24 in center joist bays needing the 3 runs so that's what I did. All the info i found also was in the slab that the tubing should be about 1 1/2 down from the top of concrete so thats what I have going on there. I'm not sure what is needed for the plates as I just figured it add it and go from there i did my best to look up good info an space things correctly. The area inside the studs is going to be a bathroom so tile floor and the other area would be left uncovered or possibly tiled. The room upstairs currently has carpet but was planning on removing and putting hardwood down. This house has forced air heat currently this just kind of developed from a slab needing poured and then figure i minds well add this in the slab cause it isn't going to happen at another time. Does the caleffi setup you show eliminate the need for two separate manifolds? I wasn't sure sorry about all the questions Thanks for the great info
  • hot_rod
    hot_rod Member Posts: 22,131
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    What are you going to heat all the radiant with. That will determine the piping options?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,002
    edited August 2022
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    What have you got there? Maybe 800 square feet total? You could possibly use a heat exchanger off your domestic water heater to heat the radiant if your water heater is large enough. This is a popular setup although they seem to be out of stock. You could also use a dedicated gas or electric water heater.

    Try not using an on-demand water heater as they are not set up for warm return water temperatures and they will short-cycle to death.
    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
    GGrossFluke216
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,833
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    If you look at that text I took the illustration from, it will give you information of pipe sizing on page 5. If all you are ever going to do with radiant heat is just that small area, then 3/4" pipe is fine. And the source for that small amount of heat can be a small heat exchanger that is taking heat from something you already have. A heat exchanger off of your water heater has been suggested, but not a tankless water heater. A heat exchanger off of your space heating boiler or perhaps a zone off the existing space heating boiler if you have one.

    I have done this with a 30 gallon tank type LP gas water heater. Just set the water temperature on the tank to the higher temperature loop and run that circulator with a thermostat and relay. Then the mixing valve for the lower temp zone with its own circulator thermostat and relay

    I'm not aware of your current heating source for the rest of the house, so I can't recommend what you should do as a source for this floor heating.

    Hope this is helpful.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • hot_rod
    hot_rod Member Posts: 22,131
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    It will be a little tricky running both a forced air and partial radiant system. The forced air will win the race, satisfy the thermostat. Then the radiant could over heat the spaces 
    Maybe consider it a floor warming system, use a two stage thermostat with a floor sensor to prevent over heating.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Fluke216
    Fluke216 Member Posts: 33
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    Alan (California Radiant) Forbes said:

    What have you got there? Maybe 800 square feet total? You could possibly use a heat exchanger off your domestic water heater to heat the radiant if your water heater is large enough. This is a popular setup although they seem to be out of stock. You could also use a dedicated gas or electric water heater.

    Try not using an on-demand water heater as they are not set up for warm return water temperatures and they will short-cycle to death.

    ok I like that idea. ok I see the tankless is not a good idea. Yes correct its about 800 sq foot 400 below and 400 above.
  • Fluke216
    Fluke216 Member Posts: 33
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    EdTheHeaterMan said:

    If you look at that text I took the illustration from, it will give you information of pipe sizing on page 5. If all you are ever going to do with radiant heat is just that small area, then 3/4" pipe is fine. And the source for that small amount of heat can be a small heat exchanger that is taking heat from something you already have. A heat exchanger off of your water heater has been suggested, but not a tankless water heater. A heat exchanger off of your space heating boiler or perhaps a zone off the existing space heating boiler if you have one.

    I have done this with a 30 gallon tank type LP gas water heater. Just set the water temperature on the tank to the higher temperature loop and run that circulator with a thermostat and relay. Then the mixing valve for the lower temp zone with its own circulator thermostat and relay

    I'm not aware of your current heating source for the rest of the house, so I can't recommend what you should do as a source for this floor heating.

    Hope this is helpful.

    Ok I see what your saying im going to look at the link for piping size thanks for that. Its going to be that area and maybe another room of a similar size 400 more sq ft at some point in the future. My wife wants to get a propane stove here soon, so I figured Id get a tank anyway and do a propane heater of some kind. Currently the heat is forced air elec and the water is elec water heater. I have a wood stove in another area. I thought about doing some type of wood boiler but didn't really nail anything down about either. thanks for the information any other comments are much appreciated.
  • Fluke216
    Fluke216 Member Posts: 33
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    hot_rod said:

    It will be a little tricky running both a forced air and partial radiant system. The forced air will win the race, satisfy the thermostat. Then the radiant could over heat the spaces 
    Maybe consider it a floor warming system, use a two stage thermostat with a floor sensor to prevent over heating.

    OK that makes sense. So this area was an additon and my idea was put a damper in the duct run to this portion and run radiant there and close off the forced air as the bill is crazy in the winter. The duct in the concrete floor portion just had a grill cut in and didnt heat very well, and it sends to branches up into the other room. Let me know what you think I greatly appreciate the information

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