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flow on system?

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HoraceHeat
HoraceHeat Member Posts: 6
in Radiant Heating
Still struggling with a zoning question I can't get my head around. How can I determine the flowrate on my current system? Its a gravity conversion with Grundfos UPS 20-42 circulator. How will I know if zone valves will constrict the system?

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  • heatpro02920
    heatpro02920 Member Posts: 991
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    I think we will need more info

    zone valves will definitely "constrict" the system, but if that will or will not inhibit proper function won't be apparent until you do the math...



    Why not forget about zone valves and use a nice circ for each zone, something variable like the bumble bee, set it up for delta t and forget about it...
  • Gordy
    Gordy Member Posts: 9,546
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    Good read

    http://www.heatinghelp.com/article/343/Circulators/238/Sizing-Circulators-for-Hot-Water-Heating-Systems



    Gravity hot water systems have very low head.



    Why not use TRVs instead of zone valves? A much better option then use a delta p, or t circ ECM flavor like the bee.
  • HoraceHeat
    HoraceHeat Member Posts: 6
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    info

    Hi Heatpro,

    lots of help on here but lots of different opinions. I have a gravity convert system in old house. 3500 sq ft, 150KBTU nat gas. 4 inch cast iron pipes, 18 radiators in main house, 2 radiators on separate circuit in sunroom...all one zone (Grunfos UPS 20-42). Want to go to two zones.



    I have two 3.5CV Honeywell zone valves, thinking I could just do it that way, but I don't know what my current flow to the main house is; I'm thinking its ~10gpm to carry ~100K? I don't know, but if so, will 3.5CV be too small?

    Thanks
  • bob_46
    bob_46 Member Posts: 813
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    Pump

    Horace , how is your existing system controlled ? Does the pump run continually or does it go on and off with the burner ?
    bob
  • HoraceHeat
    HoraceHeat Member Posts: 6
    edited August 2014
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    control

    The system is controlled by a Honeywell aquastat (can't remember model). The pump comes on when the boiler fires, which is controlled by a thermostat in the main house.



    My problem is my sunroom is always ~10 degrees colder than the main house. I want to heat it more in the evenings, less during the day. I was thinking a programable thermostat on a separate zone would do the trick. Everything works great for the main house, apart from moderate gas bill.



    I'm not sure if zone valves that I have are the correct approach...?

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