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slab heat manifold

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Brad White_9
Brad White_9 Member Posts: 2,440
in THE MAIN WALL
You are up there in terms of available outlets on a given manifold, 12 being the most common that I have seen. One inch for 5.5 GPM seems realistic too as does the 300 linear foot rule. I am assuming a 20 degree drop.

The slab in the photo does not look like 3,000 SF to me- is there more?

Just to ask: Might it make sense to have two different water temperatures, exterior versus interior and hence two different manifolds? (Assuming local mixing or are you coming straight off the boiler?)

Two manifolds will afford some redundancy should one fail and also less collateral homeruns to deal with. By splitting them into two manifolds you can also take the edge off each, allow shorter circuit lengths (why be at limit?) and more of a margin on your feeder size.

Also, I can see 12 circuit homeruns overheating the path should they not be planned correctly or if they wind up by default in a place that does not need so much heat.

My $0.02

Brad

Comments

  • aktom_2
    aktom_2 Member Posts: 3
    manifold for radiant slab

    My question is can I use one manifold to supply a 3000ft2 slab. My installer is planning on one manifold with 3000 ft of 1/2" hepex. set up with 300' loops so there will 10 1/2" supply and return lines. The heat load on the building is around 55,000 btu/hr and 2" BB under slab. The numbers say it should be OK with 1" supply and return lines to manifold. I've looked at other large shops and building and noticed multiple manifolds. Just wondering what design criteria is.
    thanks for any help here, the building is a hanger/home in Alaska.
  • Unknown
    Unknown


    for a big open space, I think you're ok. You'll have a 'hot spot' in front of the manifold.. not a big deal in a shop typically.

    The other choices would be to split the manifolds simply to ease tubing runs (doubling feed lines, maybe worthwhile if the runs are short) or to use 5/8" pipe to reduce the loop count by running longer loops. depending on the manifold hardware you are using, the loop count reduction might help pay for a step up in pipe size.

    I see absolutely no advantage to multiple water temps here. We have done multiple zones in open areas before but only in slabs much larger than yours and frankly looking back I think it was overkill then too. Temperature averaging might be useful.. maybe. but that has no impact on your manifold.
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