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Maximum water temperature recommended for concrete

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dman55
dman55 Member Posts: 1
Hi guys,
I need to know if anyone has access to any related documentation for maximum water temperature to a radiant heat slab. I have always followed what the RPA used as a guideline on 140 degrees. But I see other information out there stating 150 degrees. Any literature you can provide or link would be greatly appreciated!
Thanks

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  • hot_rod
    hot_rod Member Posts: 22,468
    edited April 2022
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    Supply water temperature? It would depend on downward losses to some extent. An uninsulated slab may need higher SWT. Plenty of the old ThawMaster car wash systems ran 160 straight from the copper tube boilers
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • pecmsg
    pecmsg Member Posts: 4,949
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    I wouldn’t recommend running 160* water in freezing cold concrete. Bring it up slowly over a few days is doable. 
  • GGross
    GGross Member Posts: 1,105
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    For my own needs I set my own "max temp" to 140 generally speaking, but I have never had any desire or need to go above that. I have seen higher temperatures and everything seemed fine, but why lose efficiency and shorten run time if not needed?

    Any context to go along with this? Inquiring minds want to know.
  • hot_rod
    hot_rod Member Posts: 22,468
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    This shows how tube placement and slab thickness changes output. Tube at the bottom, especially without any insulation would see a lot of the SWT going down.
    Seems if you are looking at 140F or higher, the loads are probably too high for a radiant concrete slab, anyhow?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    pecmsgGGross