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  • Piping a small electric tank with tankless

    I want to pipe a 6 gal electric tank inline with my tankless. Whats the best way? Series, parallel, hot side, cold side?

    My new Honeywell TrueSteam humidifiers work most efficiently with a hot water supply. Also, I might pipe a recirc to the kitchen at some point in time.

    Anyone want to help out a desperate DIY?

    Andy

  • #2
    Re: Piping a small electric tank with tankless

    Il. those winters are cold. 6 gal. as a buffer ? recirc to kitch. off the tank.

    Comment


    • #3
      Re: Piping a small electric tank with tankless

      6 gallon on the discharge side of the tankless with the recirc. piped to the 6 gal. tank.

      this will act as a buffer and will keep the wear and tear out of the tankless for the recirc.

      rick.
      phoebe it is

      Comment


      • #4
        Re: Piping a small electric tank with tankless

        Consider a velocity flow reducing device, a pump timer,aquastat or one of my favorites, wiring up the recirc pump to a light switch in the bathroom or kitchen as needed. That way you will always have hot water when the light is on and turning off the light shuts off the pump thus reducing internal pipe wear.

        Comment


        • #5
          Re: Piping a small electric tank with tankless

          Originally posted by rookie plumber View Post
          , wiring up the recirc pump to a light switch in the bathroom or kitchen as needed. That way you will always have hot water when the light is on and turning off the light shuts off the pump thus reducing internal pipe wear.

          That is F-ing Brilliant!

          Comment


          • #6
            Re: Piping a small electric tank with tankless

            Originally posted by PLUMBER RICK View Post
            6 gallon on the discharge side of the tankless with the recirc. piped to the 6 gal. tank.

            this will act as a buffer and will keep the wear and tear out of the tankless for the recirc.

            rick.
            I disagree.
            This is where location makes a difference.
            The water where he is gets drastically colder than where you are.
            The flow restrictor on his tankless is likely to slow flow when demands kicks on, regardless of the fact that he has 6 gallons of stored h/w.

            If he installs the tank prior to the tankless, he'll get more h/w when demand goes up, if he installs it after, it does virtually nothing aside from the recirc which he could install anyway before the tankless.

            I might suggest considering something larger than 6 gal though, depending on the reason he wants the tank in the first place.

            Comment


            • #7
              Re: Piping a small electric tank with tankless

              I think that was Rick's purpose Duck. Just to use a small tank for the recirc line. Not necessarily to increase capacity. And to keep wear and buildup on the tankless down.

              I've got a Rinnai schematic for it somewhere. And it's an expensive mess in my opinion.

              J.C.

              Comment


              • #8
                Re: Piping a small electric tank with tankless

                yes the 6 gallon tank is to keep the re-circ warm. it also acts as the buffer tank when the owner ask for heat. there is approx. a 6 second delay in getting hot water from a tankless. the 6 gallon tank will solve this and also help absorb the cold burst in the first 6 seconds.

                once again a 1500 watt electric bill to keep the tankless working with a circ system.

                most tankless will void/ or shorten the warranty if the circ is piped through the tankless.

                having a tank prior to the tankless will fool the tankless into thinking the water is already hot and not cause the tankless to fire.

                rick.
                phoebe it is

                Comment


                • #9
                  Re: Piping a small electric tank with tankless

                  I understand the point of the tank & recirc.

                  It can be piped it so it isn't passing through the tankless, installing it on the inlet adds the benefit of easing demand on the tankless in colder months.

                  I think I recall seeing Rinnai's schemtic..and I think it shows it piped after..makes no sense, specifically where the inlet temp sensor will restrict flow if the water is colder and demand is high.

                  Comment


                  • #10
                    Re: Piping a small electric tank with tankless

                    Originally posted by PLUMBER RICK View Post
                    yes the 6 gallon tank is to keep the re-circ warm. it also acts as the buffer tank when the owner ask for heat. there is approx. a 6 second delay in getting hot water from a tankless. the 6 gallon tank will solve this and also help absorb the cold burst in the first 6 seconds.

                    once again a 1500 watt electric bill to keep the tankless working with a circ system.

                    most tankless will void/ or shorten the warranty if the circ is piped through the tankless.

                    having a tank prior to the tankless will fool the tankless into thinking the water is already hot and not cause the tankless to fire.

                    rick.
                    Exactly, also..hot water tanks don't just suddenly go abrupty cold.
                    As the water cools, the tankless would then fire.

                    Comment


                    • #11
                      Re: Piping a small electric tank with tankless

                      Thanks for the awesome advice, guys. When I was first looking at the specs on the tankless, I had considered installing a storage tank in my basement to bring the incoming water temp up a little during the winter. During a normal winter our water doesnt really get cold until late December, (usually about the time the river freezes over and the corps closes the locks) but it usually doesnt start to warm back up til mid May. Thats about the time my cold water lines in my basement quit dripping condensation.

                      So I guess my main reasoning for adding the tank is for the kitchen recirc which I plan on making a gravity type, and to have hot water for my humidifiers. If I decide to do something about the incoming water temp I will probably look for a 30 gallon tank.

                      Not that I am trying to be a cheapass, but are 2 T&P's required on this system? I didnt know if 1 T&P per system is sufficient, or if its supposed to have 1 per appliance.

                      Andy

                      Comment


                      • #12
                        Re: Piping a small electric tank with tankless

                        Rick is correct, you do not want to put the tank heater preceding the tankless and you do not want to pipe the circ system through the tankless. All this little 6 gallon heater will be doing will be providing the instant hot water without the wait as desired by most people. The tankless heater will feed directly in and out of the tankless. It's always a good idea to insulate the feed and return lines. I've set up systems like this but have gone one step further and provided a passive (gravity) loop so the internal pipe wear is eliminated and the instant hot water is available. It works I've been doing this for more than 6 months.

                        Comment


                        • #13
                          Re: Piping a small electric tank with tankless

                          Here is a link to a Rinnai installation manual. Starting on page 24, Rinnai gives their recommendations as far as to a recirculation system. I imagine other manufacturers have their recommendations too. You will note in the Rinnai manual, they offer two examples, one will shorten the warranty, the other will not.

                          I think Takagi even has a "recirculation" model ... not sure on that though ... explore their web site and manuals for verification and recommendations ...

                          Comment


                          • #14
                            Re: Piping a small electric tank with tankless

                            Originally posted by DuckButter View Post
                            I understand the point of the tank & recirc.

                            It can be piped it so it isn't passing through the tankless, installing it on the inlet adds the benefit of easing demand on the tankless in colder months.

                            I think I recall seeing Rinnai's schemtic..and I think it shows it piped after..makes no sense, specifically where the inlet temp sensor will restrict flow if the water is colder and demand is high.
                            I need to correct that, I should have said it can be installed without using the tankless to heat the water for the tank.

                            I'm curious as to whether it would affect the warranty in this case.

                            Comment


                            • #15
                              Re: Piping a small electric tank with tankless

                              Originally posted by DuckButter View Post
                              I need to correct that, I should have said it can be installed without using the tankless to heat the water for the tank.

                              I'm curious as to whether it would affect the warranty in this case.
                              Not quite sure if I understand what you are saying ...

                              As far as Rinnai goes, if the Rinnai unit is part of the recirculation loop, the warranty drops. On page 24 of the manual, the Rinnai is not part of the recirculation loop, only the secondary water heater is, and hence the warranty stays. In their second example, the Rinnai is in the recirculation loop and hence the warranty drops.

                              So long as what you are proposing does not put the Rinnai "in the loop", I would think the full warranty would be honored. Rinnai would be the ultimate authority here however ...

                              Comment

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