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Snow melt boiler

Are there any ModCon boilers approved for use with Glycol? I have a customer who doesn't want make up water for boiler, just glycol feed tank. This is for snow melt of 1500 sq. ft. driveway in Northern Illinois.


  • Zman
    Zman Member Posts: 7,446
    I believe they are all approved for glycol. The question is, which models can run at 50%. Triangle tube and Lochinvar have approved 50% in the firetube models in the past. I have not checked the most recent I&O's
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    Bob Sersen
  • GroundUp
    GroundUp Member Posts: 1,573
    edited August 2019
    I haven't seen one that doesn't allow glycol, but for only 1500 sq ft in likely a single zone there should be no need for a glycol feeder. Maybe 40 gallon total system volume? Even in the frozen tundra of MN, I've never needed more than 40% in a snowmelt system. My system at home gets tinkered with and abused very hard on a regular basis, simply to test the limits. We had a -42F morning last winter and my bare sidewalk with 40% propylene was pumpable and making heat in about a minute
  • Bob Sersen
    Bob Sersen Member Posts: 4
    The glycol feeder takes the place of make up water to boiler, which is required for any system to protect the boiler in case of a leak. I'll check some I&O manuals, but many of them want a heat exchanger between the boiler loop and glycol system
  • GroundUp
    GroundUp Member Posts: 1,573
    I know what the feeder is for, my point is that radiant systems don't just develop a leak. Boilers (any I've seen, anyway) have a LWCO to protect themselves in the event of low water and snowmelt is not a life safety system. If there is a leak it needs to be addressed, not band-aided by a glycol feeder. Do you have a particular boiler in mind? I run primarily HTP, Laars, and Lochinvar but I have never heard of any brand requiring a HX for glycol