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I'm going to daisy chain TWO on demand heaters!!!!!!!!!!!!

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  • #16
    Re: I'm going to daisy chain TWO on demand heaters!!!!!!!!!!!!

    Originally posted by ToUtahNow View Post
    I believe if you look at the Rinnai Web Site they brag about a couple of homes in the 2006 Builders Show which had their heaters installed in series to increase the capacity.

    Mark
    That's insane and intriguing at the same time. Do you have a link? I would like to see how that worked out. It would have to be setup up with controls of some sort or the limits would trip on the second unit. You could also have problems with scolding. Here is how I could see it actually working in series. It would only fire the first unit until a certain gpm's were going through the unit, this would be measured by temp rise. If the 1st stage unit was on with full flow and the temp rise wasn't being met, the 2nd unit would kick on heating the water to the proper temperature. This would make sense, but you would have to add additional controls. This is very interesting for some reason. You could also run this same setup (1st and 2nd stage) using a solenoid valve that opened on the second unit hot outlet when temp rise isn't being reached. Plumbing just became a lot more interesting to me. Feed me some knowledge Utah (please).

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    • #17
      Re: I'm going to daisy chain TWO on demand heaters!!!!!!!!!!!!

      Originally posted by fronty View Post
      Feed me some knowledge Utah (please).
      It's a trap. Step away from the keyboard. Just a joke.
      Buy cheap, buy twice.

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      • #18
        Re: I'm going to daisy chain TWO on demand heaters!!!!!!!!!!!!

        I just looked in my Rinnai installation manual and it shows the heaters piped in parallel.
        Buy cheap, buy twice.

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        • #19
          Re: I'm going to daisy chain TWO on demand heaters!!!!!!!!!!!!

          Whether the multiple tankless heaters are installed in parallel or series depends on what you are trying to do. However, whenever installing multiple tankless heaters in close proximity you are suppose to tie them into a single control unit which controls all units.

          In theory with a tankless heater the higher the GPM flow through the heater the lower the TD. With the second heater you still have the same flow but because your TD is the same but your incoming water is hotter your supply temperature is higher.

          Mark
          "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

          I never lost a cent on the jobs I didn't get!

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          • #20
            Re: I'm going to daisy chain TWO on demand heaters!!!!!!!!!!!!

            Originally posted by gear junkie View Post
            I just looked in my Rinnai installation manual and it shows the heaters piped in parallel.
            Consider on the East coast where you might have a supply at 40 degrees but can only get 65 degree TD out of your tankless what do you do for your dishwasher. At 104 degrees you will have a perfect shower as long as you don't blend the water but what do you do to dissolve the soap in the dishwasher where the soap requires 140 degrees to dissolve?

            Mark

            BTW: Another neat use for a tankless is in series with a solar system. You eliminate your storage tank and because your supply temp is high you can get away with a smaller electric tankless.
            Last edited by ToUtahNow; 01-04-2008, 07:28 PM.
            "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

            I never lost a cent on the jobs I didn't get!

            Comment


            • #21
              Re: I'm going to daisy chain TWO on demand heaters!!!!!!!!!!!!

              Originally posted by gear junkie View Post
              I just looked in my Rinnai installation manual and it shows the heaters piped in parallel.
              Parallel is a much more common installation than series.

              Mark
              "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

              I never lost a cent on the jobs I didn't get!

              Comment


              • #22
                Re: I'm going to daisy chain TWO on demand heaters!!!!!!!!!!!!

                Originally posted by ToUtahNow View Post
                Consider on the East coast where you might have a supply at 40 degrees but can only get 65 degree TD out of your tankless what do you do for your dishwasher. At 104 degrees you will have a perfect shower as long as you don't blend the water but what do you do to dissolve the soap in the dishwasher where the soap requires 140 degrees to dissolve?

                Mark

                BTW: Another neat use for a tankless is in series with a solar system. You eliminate your storage tank and because your supply temp is high you can get away with a smaller electric tankless.
                I was thinking that as well. If the ground water is extremely cold, you could run it in parallel, but I would think every manufacturer has a maximum inlet temp. Right?


                EDIT: I MEANT SERIES NOT PARALLEL
                Last edited by fronty; 01-04-2008, 09:13 PM.

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                • #23
                  Re: I'm going to daisy chain TWO on demand heaters!!!!!!!!!!!!

                  The reason I think tankless in parallel would be a better idea is the flow restriction feature they come with.
                  I could imagine a humorous batch of problems with two of them parallel and the flow restriction kicks on with one...the sudden burst of flow cause the next one's restrictor to kick on..and so on.
                  No doubt thats why you need a CPU to run both in parallel.
                  In series, I imagine it's a "weakest link" scenario...if a restrictor kicks in on one, the flow is completely slowed for all hot water.

                  Ben...btw...it's steak...just hadda get that before it got cold.

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                  • #24
                    Re: I'm going to daisy chain TWO on demand heaters!!!!!!!!!!!!

                    Originally posted by fronty View Post
                    I was thinking that as well. If the ground water is extremely cold, you could run it in parallel, but I would think every manufacturer has a maximum inlet temp. Right?
                    There may be some that do but consider the limits it would put on a circulated system if that were true. I have a project in Laughlin with a 104 degree incoming water which would be perfect for tankless heaters.

                    Mark
                    "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

                    I never lost a cent on the jobs I didn't get!

                    Comment


                    • #25
                      Re: I'm going to daisy chain TWO on demand heaters!!!!!!!!!!!!

                      Hooked two of the large Rinnias up in parallel with a hundred gallon storage tank and recirc pump.Don't ask me why,thats what the homeowner's smart guy said was the way to go.His wife needs a lot of hot water for her master tub valve after bathing kids.

                      I remember bringing this up when I was new here.I think I got rebuked for using the wrong terminology.The thread died out shortly after.

                      I like seeing this one go so much farther.Lots of knowlegeable additions since then
                      Last edited by drtyhands; 01-04-2008, 08:40 PM.

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                      • #26
                        Re: I'm going to daisy chain TWO on demand heaters!!!!!!!!!!!!

                        Rinnai states that if you will be installing 2 or more hot water heaters, they must be installed in parallel. Ask any rep or call any tech support for rinnai, and they will tell you the same.

                        I am sure that the same goes for any other tankless companies also.
                        sigpic

                        Robert

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                        • #27
                          Re: I'm going to daisy chain TWO on demand heaters!!!!!!!!!!!!

                          Originally posted by drtyhands View Post
                          Hooked two of the large Rinnias up in parallel with a hundred gallon storage tank and recirc pump.Don't ask me why,thats what the homeowner's smart guy said was the way to go.His wife needs a lot of hot water for her master tub valve after bathing kids.

                          I remember bringing this up when I was new here.I think I got rebuked for using the wrong terminology.The thread died out shortly after.

                          I like seeing this one go so much farther.Lots of knowlegeable additions since then
                          The storage tank seems alittle overkill, but rinnai and many other tankless manufactuers want the recirc loop tied off a storage tank, or even better, and electric water heater,t hey do not want the recirc feeding off the tankless itself, it changes or voids the warrenty.
                          sigpic

                          Robert

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                          • #28
                            Re: I'm going to daisy chain TWO on demand heaters!!!!!!!!!!!!

                            Originally posted by ToUtahNow View Post
                            There may be some that do but consider the limits it would put on a circulated system if that were true. I have a project in Laughlin with a 104 degree incoming water which would be perfect for tankless heaters.

                            Mark
                            Yikes, 104 degrees.

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                            • #29
                              Re: I'm going to daisy chain TWO on demand heaters!!!!!!!!!!!!

                              Originally posted by westcoastplumber View Post
                              Rinnai states that if you will be installing 2 or more hot water heaters, they must be installed in parallel. Ask any rep or call any tech support for rinnai, and they will tell you the same.

                              I am sure that the same goes for any other tankless companies also.
                              WC, I know you probably are irritated with me and the other thread, but I need help in ordering isolation valves and a relief valve. Do you think you can help me out? You seem to have extensive knowledge in tankless systems.

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                              • #30
                                Re: I'm going to daisy chain TWO on demand heaters!!!!!!!!!!!!

                                Been a Rinnai dealer and installer for quite a while now. Never heard of series piping them. Always paralell.
                                sigpic

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