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Adding a hydronic zone to a steam system

smokes Member Posts: 9
Hey - I have a steam system running off a Burnham about 10 years old, with a hydronic baseboard loop in the basement with its own simple honywell 120v thermostat and circulator pump. The thermostat basically controls the circulator pump not the boiler.

My question is can i set up the system so the hot water loop will call for heat and fire up the boiler without burning up the radiators upstairs?

if not, would it be practical to add a tankless water heater to run the basement heat seperately? Can that set up work?


  • Jamie Hall
    Jamie Hall Member Posts: 22,934
    It's late at night so I'll be quick

    and others will probably expand on my comments...

    Yes, you can set up an aquastat to run the boiler when the hydronic zone calls for heat and the boiler water isn't hot enough.  No, there is no simple way to keep the boiler from then heating the radiators upstairs.  It might, it might not, depending on how you have the controls wired and a few other factors -- and it wouldn't be very consistent.  Tankless water heaters are not, in general, recommended for use on hydronic heat systems...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Steamhead
    Steamhead Member Posts: 16,729

    it can be done, and will work well. The key is wiring the aquastat so it won't let the boiler make steam when only the HW loop is calling. 
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • smokes
    smokes Member Posts: 9

    Thank you, gentlemen and scholars! Its amazing how you can get great answers on this website! I'll check with my plumbing supply and let you know how it works out.
  • JeffM
    JeffM Member Posts: 182
    commonly done

    Your aquastat would be just like the ones used to control tankless coils in a boiler - they keep the boiler hot, but shut it off before it boils so you're not sending steam to the radiators just by running a hot water faucet. 
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