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Hydronic System with In-slab, Radiators & Water Heating

Santilal Member Posts: 42
Someone recently showed me a really simple hydronic design which I have sketched up and attached. I haven't shown the expansion vessels, check valves etc, but have shown enough detail (hopefully) to describe the principle. The system has water heating, radiators and in-slab heating. The in-slab circuits each have their own thermostats and electrically operated valves. The radiators each have a thermostatic valve. The main circulator is fitted into the Caleffi Anti Condensation Valve (Type 281066). The flow rate in the main loop is about 5.5gpm. The flowrate through the water heating and in-slab circuit is about 2gpm. The flow restrictor/meter is there to restrict the flow to 2gpm and monitor it from time to time. It might also be possible to replace the circulator with an Alpah 2.

The design seems so simple that I think there must be a catch but maybe I'm wrong. I was wondering anyone had any thoughts on this.




  • Zman
    Zman Member Posts: 7,573
    I sure wouldn't put one in like that.
    My main concern would be the fluctuation in flow rates to the system based on return water temps. Any time the thermostatic mixing valve closes, all flow stops to the system. If the radiant system is significant, when it cold starts it will drop the return temp and shut everything down until it warms up.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Rich_49
    Rich_49 Member Posts: 2,766
    Please allow us to see the entire drawing including the parts you have omitted
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • Santilal
    Santilal Member Posts: 42
    Thanks for the comments. I didn't think about the reduced flow, Zman. I will pass that comment on to the person who told me about this idea. Rich, I will have to sketch up how the rest of the system would go. Will try to do that today. It is not an actual system but a suggestion from an installer I just happened to be talking to. I am interested in hydronic systems because I have one myself and I am always interested in talking to others who have them or install them to gain other perspectives. Thanks.
  • hot_rod
    hot_rod Member Posts: 22,256
    There are a number of better piping arrangements, here is a book full of best practice ideas.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream