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Radiant with W/H

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  • Radiant with W/H

    Any recommendations on W/H (no boilers) to use for radiant heat in concrete slab? About 1200 sq.ft. of heated space. Normal residential insulation.

    Also, 3/4" or 1/2" PEX?

    Oxygen barrier?

    Thanks for all opinions.

    J.C.

  • #2
    Re: Radiant with W/H

    http://www.bradfordwhite.com/images/...eets/545-B.pdf

    a few zones of 1/2" should be fine

    Yes to the oxygen barrier

    Comment


    • #3
      Re: Radiant with W/H

      PC. Got ZERO experience installing or troubleshooting. What I'm reading is that no O2 barrier required with a water heater but should be used with a boiler.

      I've also read that 1200 sq.ft. (estimated) could be handled easily with 1 pump, stat, & heater. 1 big zone so to speak.

      This what I've read though. Experience means as much or more.

      Does any of this sound right?

      Thanks.

      J.C.

      Comment


      • #4
        Re: Radiant with W/H

        Originally posted by JCsPlumbing View Post
        PC. Got ZERO experience installing or troubleshooting. What I'm reading is that no O2 barrier required with a water heater but should be used with a boiler.

        I've also read that 1200 sq.ft. (estimated) could be handled easily with 1 pump, stat, & heater. 1 big zone so to speak.

        This what I've read though. Experience means as much or more.

        Does any of this sound right?

        Thanks.

        J.C.
        First you need to find out a few things....

        is the heater a primary heat source for the space?

        what is the actual heat loss?

        how much domestic hot water is needed?

        no loop should be over 300' in length you will a manifold with at least 4 circuits and a pump to overcome the head loss.

        I've heard good things about this new Zurn product but have never used it myself
        http://www.zurnpex.com/Portals/4/ZNPA182.pdf

        Comment


        • #5
          Re: Radiant with W/H

          While I may have some of your eyes & ears....How do you keep from hitting a radiant line in the slab? Like when carpenters are setting baseplates with a RamSet? The radiant is in the slab.

          Any ideas or am I overthinking?

          Thanks.

          J.C.

          Comment


          • #6
            Re: Radiant with W/H

            Tube mat and circuits should be "fit" by arch.

            Comment


            • #7
              Re: Radiant with W/H

              Originally posted by stokefire7 View Post
              Tube mat and circuits should be "fit" by arch.
              Meaning Architect? Architect pretty much never used here on anything that small.

              If not-what does arch mean?

              J.C.

              Comment


              • #8
                Re: Radiant with W/H

                Yes , You have some idea as to where the walls are going or zones.

                Comment


                • #9
                  Re: Radiant with W/H

                  Originally posted by stokefire7 View Post
                  Yes , You have some idea as to where the walls are going or zones.
                  Gotcha'. Yes you would by blueprints. But unless I'm missing something you could have dozens, maybe even a hundred. of crossing points for the radiant under the interior walls that couldn't be avoided.

                  Showing my lack of experience with radiant probably.

                  Thanks.

                  J.C.

                  Comment


                  • #10
                    Re: Radiant with W/H

                    Generally the piping doesnt get ran out to the edge of the slab where anchoring the bottom plate would interfere. I usually stay about 9 inches away from the edge. Every design I have ever had done for me shows the piping 9 inches on center, but bending that tight of a radius is something totally different. I space all mine at 12 inches.

                    What PC said is exactly right. You will need 4 loops. A good rule of thumb is 1 linear foot of pipe for every 1 square foot of floor space.

                    Without knowing the heat loss its kind of hard to size a heater for you. Im guessing a 40k 40 gal would do the job, but it could also need a 50/50. What are the rest of the specs on the building? I recommend installing a tempering valve to control the return temperature. I installed a 60k 50 gallon in my friends 30x54 shop. I set the water temp at 90 degrees. For whatever reason he cranked it up a few years later. His first heater lasted 6 years. His second one lasted 2 years with the heater at 120 degrees. I just bought him a damaged WM CGI5 and its for sure going to have a tempering valve.

                    Andy

                    Comment


                    • #11
                      Re: Radiant with W/H

                      No, it's a genuine concern. Plans change, wall layouts change so you have to be aware of the tubing at all times.

                      When laying out my radiant I took no less than a hundred photos of tubing placement before the pour. I left mine deep in the concrete for the fear of a puncture. The concrete guys kept wanting to pull it to the surface.

                      I lost some effectiveness by leaving it deep but no worries during wall layout

                      No Ramsets used but several cases of Liquid Nails were

                      Biggest concern was where the tubing penetrates through the slab

                      Comment


                      • #12
                        Re: Radiant with W/H

                        Yes, the concrete boys have been told to pull the wire up in the slab.

                        Better for the slab but not for radiant.

                        Ruudaca-You say keeping the temp down to around 90 but what I've seen done a couple of times here is using the W/H for heat and hot water. 90's would obviously be too low.

                        Did I misunderstand? Too many questions yet?

                        I could read a book if you guys tell me too.

                        J.C.

                        Comment


                        • #13
                          Re: Radiant with W/H

                          RuudaGuy?

                          Comment


                          • #14
                            Re: Radiant with W/H

                            Crank the heater as high as it will go (+140) Temper the water back down on domestic (120) AND radiant (90?) side.

                            And yes you will need a new heater within 5 years.

                            Best to put your money towards a high efficiency boiler with indirect fired tank.

                            Comment


                            • #15
                              Re: Radiant with W/H

                              Thanks for all the help. Better understanding.

                              J.C.

                              Comment

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