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Tankless w/storage tank question

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  • Tankless w/storage tank question

    I have a friend who is also an owner of a one-man shop and will be installing a Rinnai in the configuration of the diagram I have included.

    Sorry for the dumb question but if a check valve is not installed where I have indicated in red, what's to keep the cold inlet water from entering directly into the storage tank when water is drawn in the house?
    Attached Files
    Last edited by SlimTim; 05-03-2008, 11:31 PM.
    "Man will do many things to get himself loved, he will do all things to get himself envied." Mark Twain

  • #2
    Re: Tankless w/storage tank question

    Where?

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    • #3
      Re: Tankless w/storage tank question

      I had to save it and enlarge it to see what was going on in that picture, but your right, there should be a check valve where you indicated.
      Proud To Be Union!!

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      • #4
        Re: Tankless w/storage tank question

        Ok, off the original subject. How do I get a jpeg directly into my post? I see it done but I can only seem to get a thumbnail which links to a somewhat larger pic
        "Man will do many things to get himself loved, he will do all things to get himself envied." Mark Twain

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        • #5
          Re: Tankless w/storage tank question

          Doesn't Rinnia reduce their warranty when we run a pump through the heater.

          A clock and thermoswitch will cut down on unneeded heater usage.

          Do they say anything about installing them to help on the waranty

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          • #6
            Re: Tankless w/storage tank question

            on a commercial application such as a larrs or raypack unit, there is a pump to circulate between the tank and the heater. actually it's necessary so that you don't have to heat to the full 50-120 degree range. but instead just a 20 degree rise.

            now on your situation there can be a draw of cold if the circ pump is not running.

            i just looked at a noritz installation book i have.

            there are 2 examples.

            small residential example shows the recirc line teeing back into the heater. plus a small buffer tank with a hot in and hot out feeding the fixtures. along with a aquastat, timer, internal pump control feature.

            on the commercial installation with storage tank, there is a recirc pump between the storage tank and the tankless. similar to how i described the larrs and raypack installation.

            so to be honest, i would say there is an issue if the pump i not running when the water is being used. is there a pump controller circuit that needs to be wired in?

            rick.

            rick.
            phoebe it is

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            • #7
              Re: Tankless w/storage tank question

              Originally posted by PLUMBER RICK View Post
              is there a pump controller circuit that needs to be wired in?
              rick.
              There is only the AquaStat. This is a burn job. There was a similar setup before the fire. I have included a drawing I did on Microsoft paint of the original setup. I've left out the relief valve for clarity but did include the only check valve there was.

              I think I prefer the Rinnai configuration except I would add a check valve as mentioned before. Do you see a problem with adding that check valve?
              Attached Files
              "Man will do many things to get himself loved, he will do all things to get himself envied." Mark Twain

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              • #8
                Re: Tankless w/storage tank question

                It appears to me that in that configuration, the Rannai is being used more to reheat the tank after the draw, not as an instant water heater. How big is the tank?
                sigpic3:00, I mean 5:00, and work is done. Time to crack a cold one.

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                • #9
                  Re: Tankless w/storage tank question

                  It is recommended you feed the recirc loop off a storage tank, or better yet, a little electric water heater, for warranty only.

                  In the rinnai book, which is where the first drawing came from, the tankless is heating the water in the storage tank, and the storage tank is feeding the fixtures, and the recir pump is keeping that water hot

                  Instead of doing all that, I would probably install the Hybrid water heater, any time the customer has a recirculation line or storage tanks, I always introduce the Hybrid water heater to the customer as a better option.

                  This unit will handle a recirc without loss of warranty, because it has a 8 gallon tank inside.

                  http://www.eternalwaterheater.com/products.php
                  sigpic

                  Robert

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                  • #10
                    Re: Tankless w/storage tank question

                    Very nice Robert. If you review this months Reeves Journal they have quit a bit on "Green" water heating including the hybrid water heaters.

                    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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                    • #11
                      Re: Tankless w/storage tank question

                      Originally posted by westcoastplumber View Post
                      Instead of doing all that, I would probably install the Hybrid water heater, any time the customer has a recirculation line or storage tanks, I always introduce the Hybrid water heater to the customer as a better option.

                      This unit will handle a recirc without loss of warranty, because it has a 8 gallon tank inside.


                      Well, that is an impressive looking tank and design but I see the gpm at 90 degree rise for the smaller version is only 3.5 gpm. And my experience is the more bells and whistles, the more that can go wrong. Which wouldn't be an issue if there were parts and repairmen readily available as in HVAC for example.
                      But, I would still consider it if the gpm weren't so low.
                      "Man will do many things to get himself loved, he will do all things to get himself envied." Mark Twain

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                      • #12
                        Re: Tankless w/storage tank question

                        I just noticed your degree rise, it all makes since now....you have colder water

                        We are lucky here in los angeles
                        sigpic

                        Robert

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                        • #13
                          Re: Tankless w/storage tank question

                          Originally posted by westcoastplumber View Post
                          I just noticed your degree rise, it all makes since now....you have colder water

                          We are lucky here in los angeles
                          Uh, that's a matter of opinion.
                          "Man will do many things to get himself loved, he will do all things to get himself envied." Mark Twain

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