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Flow rate, what is ideal for in floor hydronics?

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  • Flow rate, what is ideal for in floor hydronics?

    I am running a single zone with 2 loops. Loops are 150' each. I have a taco 3 speed pump. On low speed I am doing about 6 gallons per minute per loop. What is the ideal speed? Also, If my flow rate is too fast should I use a flow control to slow it down? What kind?

    Regards.

  • #2
    Re: Flow rate, what is ideal for in floor hydronics?

    Not a very experienced hydronics guy but what kind of TD is your heating source looking for??

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    • #3
      Re: Flow rate, what is ideal for in floor hydronics?

      Chris,

      300' of tubing would not be considered a small zone. What's the square footage and spacing on the tubing?

      6 GPM is too fast for this zone. You want to be somewhere in the 2-4 GPM range. The Grundfos 3 speed pump will work but not recommended.

      I would have broken it out to at least 3 loops with less footage on each loop.

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      • #4
        Re: Flow rate, what is ideal for in floor hydronics?

        Originally posted by plumberscrack View Post
        Chris,

        300' of tubing would not be considered a small zone. What's the square footage and spacing on the tubing?

        6 GPM is too fast for this zone. You want to be somewhere in the 2-4 GPM range. The Grundfos 3 speed pump will work but not recommended.

        I would have broken it out to at least 3 loops with less footage on each loop.
        Square footage is only 250 sq' . spacing is about 10", as I said 2 loops 150' each. 3 loops of 100' didnt make sense to me for such a small area. Many people run 1/2" in 300' single loops.
        The reason I am asking about flow rate is that my return temp is less than 10 degrees lower than supply temp.

        Chris

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        • #5
          Re: Flow rate, what is ideal for in floor hydronics?

          In slab or staple up? What is the outlet temp? are you using a tempering valve or injection? Finally single or multi speed circulator?
          sigpic

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          • #6
            Re: Flow rate, what is ideal for in floor hydronics?

            Originally posted by NHMaster3015 View Post
            In slab or staple up? What is the outlet temp? are you using a tempering valve or injection? Finally single or multi speed circulator?
            Tubing will be covered with 1 1/2" of thermafloor gypcrete. Outlet temp is 125 or so (thermafloor has a recommended maximum of 140 degrees) I have a taco 3 speed circulator

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            • #7
              Re: Flow rate, what is ideal for in floor hydronics?

              depends mainly on type of boiler, call manufacturer tell them what you got.

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              • #8
                Re: Flow rate, what is ideal for in floor hydronics?

                Drop the salb inlet temp to around 90 to 95 degrees and run the circulator on slow speed. Make sure you are doing primary secondary piping off the boiler.
                sigpic

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                • #9
                  Re: Flow rate, what is ideal for in floor hydronics?

                  First you need to know the pipe diameter, you know the length,(which is 150'), then the BTU/H per sq. ft. needed to heat the room. The normal Delta T is 20 degrees. You are running too much water too fast. A lot of my systems are 330' of 1/2" pex and I use a IR flow meter to balance and typically see .8 to 1.4 gpm. per loop. The Wirsbo C-DAM Manual shows these flow rates for their respective diameter, length with the desired BTU/H sq. ft. at 100% water or whatever % of prop. glycol mixture. Thats how you select the pump with the proper gpm at the proper head(pump curve) I just joined the forum, good luck.

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