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snow melt

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James Bates
James Bates Member Posts: 30
in Radiant Heating
Installed 1/2 in. pex in a concrete driveway 4 yrs. ago without any insulation, and am finally completing the hook-up. How high a temperature will be needed for it to be effective? Is there a danger of cracking the concrete if you go too high with the temperature? I know now it could have been installed better, but I'm stuck with it and would like to be able to use it...

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  • NRT_Rob
    NRT_Rob Member Posts: 1,013
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    uh,

    that looks like it's 18" o.c., or maybe 12" o.c. not good.



    You used 1/2" pipe that will never carry enough flow to do a snowmelt load unless these loops are tiny, tiny, tiny. maybe 150 feet max or so.



    In short: I doubt you will make this effectively melt snow at any temp. Sorry to be the bearer of bad news.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • James Bates
    James Bates Member Posts: 30
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    Snow Melt

    The loops are 150 ft., 12in. to 18 in. apart. Would a high temperature help?
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
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    Expect striping....

    Increasing the temperature increases the possibility of thermally shocking the concrete and causing spalling and cracking. It's not rocket science, but it does require some attention to detail.



    ME

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  • CMadatMe
    CMadatMe Member Posts: 3,086
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    Leaving Out that Insulation

    Hurt you alot. Could have done it had you insulated. Like the others state be real careful. Your oil or gas company is going to be you new best friend once you start firing that driveway up. Your wife will love you though. You just gave here some turf conditioning along the sides of that driveway. She can grow some pretty flowers all year round now.

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  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
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    Questions for James...

    Curious to know,



    What compelled you to do your own snowmelt system?



    Did you do any research prior to doing it?



    Did you seek guidance from a knowledgeable person?



    Was the idea of insulation ever touched upon?



    What caused you to come to this site after the fact?



    If you answer these and fulfill my curious mind, I will make some mechanical suggestions that MIGHT allow the snowmelt to work to 75% of its capacity, without having to have a 2 HP pump :-)



    ME.

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  • CMadatMe
    CMadatMe Member Posts: 3,086
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    Hail Mary

    I would take Mark up  on his willing to help you out of a big jam. Your sitting on the 50 with 1 second left. If I'm thinking correctly Mark is going to tell you how to stretch that delta-t to get some btu's out of that melt.

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  • James Bates
    James Bates Member Posts: 30
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    answers to questions

    I was having the driveway done the next day, when snowmelt was suggested to me by my plumber. I delayed it one day and he installed the pex with my help. I obviously had no time for research and I trusted his knowledge.



    Insulation was never brought up at the time, which turns out to be 8 yrs. ago, not 4 yrs. as previously stated. When you live in a house for 30 yrs., you definitely lose track of time.



    I first came to this site 4 yrs. ago, when the same plumber could not figure out what was wrong with my 1929, 2 pipe, trane steam system. "Steamhead" came to my rescue and suggested some changes that needed to be done. It has run flawlessly ever since. Thanks, again.



    I'm hoping there is some way I can get this to run with what I am stuck with...
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
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    Thank you for the answers...

    The lack of insulation is going to add operating expense to an already expensive operating cost. We normally load these things at around 125 to 150 btu/sq ft/hour. In your case, it will be less, but the net effect will also be less. Expect striping.



    You are going to have to use a modulating condensing heat source for this to work.



    Once the head pressure drop has been calculated, and the pump sized for the application, you can apply a 4 way valve as a reversing valve. I will have to generate a drawing on another PC to demonstrate the piping arrangement.



    Essentially what this will do is reverse the flow through the circuits based on a timed function. Typically 10 minutes per direction.



    This will essentially take what is an excessively long circuit and cut it in half as it pertains to heat transfer. The pressure drop is still based on the whole circuit.



    Snowmelt, although not rocket science, does require a fair amount of planning and design to be efficient and effective.



    Hang on to Frank. He's a keeper.



    As Ahnold Schwartzeneger said, I will be back...



    ME

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  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
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    The drawing...

    Obvioulsly, this is a simple schematic outline.



    It WILL spread the heat around.



    ME

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