Adding Glycol to snow melt system

Discussion in 'Boiler Forum' started by thompsonblake, Jan 20, 2012.

  1. thompsonblake

    thompsonblake New Member

    Joined:
    Jan 20, 2012
    Location:
    Nova Scotia
    Currently working on installing a closed loop snowmelt system for a driveway roughly 38x18. Using 3 loops (1 zone) at around 300 feet runs (3/4 HePex, 9 inch centres) Im adding this system to an existing boiler that does have enough BTUs to heat the system. Laying the pipe and building the headers is fairly straight forward and I have done countless times. However my journeyman has always handled the more detailed boiler work such as, pump size, heat exchanger, expansion tank size. More importantly i have calculated that i need a 40% glycol mixture but am not sure the best method for adding and maintaining the glycol in the system.

    Any help would be appreciated but i guess I'm looking for the best method for adding glycol and maintaining glycol levels, and possibly a simple diagram boiler system.
     
    Last edited: Jan 20, 2012
  2. DonL

    DonL Jack of all trades Master of one

    Joined:
    Mar 30, 2011
    Occupation:
    Rocket Scientist
    Location:
    Houston, TX

    This is what they use down south of you. They work good.


    Snow_Shovel.jpg
     
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  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    When I ran a system with antifreeze in it, when the techs filled it, they first determined how much they needed, then they had a hose bib on the suction side of the pump, put a hose on it and sucked the required amount of antifreeze in from the bottles, then turned on the autofill to fill it the rest of the way with water. So, if you figured the tubing was a long cylinder, figured its volume in cuin, then divide by 231, you'd have gallons.

    Unless you run the external system off of a heat exchanger, that means adding the antifreeze to the whole system as well, so you need to figure that volume out, too. A heat exchanger is probably not a bad idea. Also, keep in mind that the antifreeze DECREASES the efficiency of heat transfer, so in effect, the boiler doesn't look as big as if you were using all water. This also may affect the spacing and lengths of your radiant loop(s). I don't remember that factor, but you should be able to find it if you search a bit...I think it was in the 10% range, but don't quote me.
     
  5. thompsonblake

    thompsonblake New Member

    Joined:
    Jan 20, 2012
    Location:
    Nova Scotia
    Thanks for your help Jim, i think the heat exchanger sounds best as well as i don't want to decrease the efficiency off the whole system by running glycol through it. Would a heat exchanger with a closed loop from the boiler on one side and the supply to my smowmelt headers on the other, be enough to heat the system properly? There are detailed installation instructions on the uponorpro tutorials page but they really only deal with systems that are strictly for snowmelt.
     
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
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