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  • OT-Tankless water heaters

    Thinking about installing a tankless water heater for one small bathroom. This would be for a shower and a lavatory. Does anyone have any thoughts about the wisdom of such a move. Years ago, I had a tankless water heater at this bathroom that didn't work so well. It was when they were first available. This one was made in England and came with British sized copper fittings. It didn't last very long. The electric's crapped out after about 3 months. Does anyone have recommendations as to brand or any other thoughts.
    Sarge41

  • #2
    Horrible things! They do not heat water to a fixed temperature, but rather they raise it above the input temperature by an amount that depends on the flow rate. So if the incoming water is cold, the output will be cool unless the flow rate is slow. Conversely, if the incoming water is already warm, the output water will be very hot. And if someone else in the house turns on a tap and thereby affects the water pressure, your flow rate will drop and you will be scalded.
    How do I know? I have lived with these things in a house as well as on a boat and in a campervan—and I hate them! Nothing would ever persuade me to install one again.

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    • #3


      mike Burch:

      Flow-rate sensitivity can be mitigated somewhat with pressure-balancing/anti-scald valves.

      @sarge41:

      I used to employ electric tankless water heaters to boost the output from an aging oil-fired tankless heater: worked OK - but the electric heaters are not robust - I ran through 3 successive heaters from one manufacturer plus one from a different manufacturer - all failed after less than a years service. The better choice is a conventional electric hot water tank, a gas-fired tankless water heater, or a heat-exchanger coil + tank plumbed to a central heating plant.

      Edit: (1) my experience with these devices is 30 to 35 years old, so I'm hardly current with the technology (2) I was trying to provide hot water for an entire house - this was imposing maximum load & duration on the tankless heater.
      Last edited by tlfamm; 05-28-2021, 08:59 PM.

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      • #4
        Ahem...that is why they are called "thankless" water heaters....

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        • #5
          About 5 years ago, I installed a Stiebel Eltron 24 KW 4.68 gpm tanless heater out in our garage. It supplies hot water to the laundry and our guest bed/bath. I works great!!!! It has two heating elements in it that each has it's own 240volt electrical supply.
          I think most people don't get a big enough heater. you want to figure your GPM need, and then go to the next size up. We can set what temperature we want the water to be. Our biggest use in the washing machine and supplies it just fine. It reduced our electrical power bill by a lot be cause it is only heating water as you use it.
          I have made up my mind to when ever we need to replace the tank water heater in the house we will install the 3 element tankless heater.
          _____________________________________________

          I would rather have tools that I never use, than not have a tool I need.
          Oregon Coast

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          • #6
            My last electric tankless heater was a single-coil, 220 volt, 40-amp stainless vessel (a little larger than an oil filter) with adjustable temperature. In operation it would cause the lights in my house (and my neighbors) to flicker. Even after Boston Edison installed a dedicated transformer & pole for my house, the flickering did not stop. Problem was solved 5 months later when the unit failed.

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            • #7
              We installed a natural gas one for our present house when we moved in about 5 years ago. I am 100% happy with it. My impression is that for the electric ones most North American homes, even those with a 200AMP service, would still require an upgrade to be able to power it and the rest of the usual things people use these days, if it was to service the entire house.

              A tanked electric heater is also using electricity. Whether more or less than a tankless one depends on your usage patterns. The trade-off is "a huge electrical demand for a short time, while you use it" vs "less electric demand but over a longer time, then conserve that energy with good insulation for the tank". Your system has to be able to meet that peak demand, even if it only needs to for several minutes each day.
              "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979

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              • #8
                At the time that I was experimenting with electric tankless water heaters, I spoke with EPRI (Electric Power Research Institute) about them: they were not in favor of them, and branded them an "unfriendly load" - in my case, I would say that was an accurate characterization.

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                • #9
                  I have a water heater heated by the oil feed house burner. It only suplyes heat in the winter and the water heater in the summer.The burner. It is a blue tank the heater. Have it for 5 Years and no problem so far. Great system.
                  Hilmar

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                  • #10
                    I've had a gas tankless water heater for the last 4 or 5 years, it is fantastic. Ours is a Rinnai. It throttles the burner up and down as necessary to compensate for both temperature and demand or water flow, works great.

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                    • #11
                      What a lot of people don't realize about tankless is they gulp energy, usually requiring bigger circuits or gas pipes and vents than are available. Some have tried to convince me to use them in my little gas rentals, but I heat them with a 40 gal tank heater that also give domestic hot water. Tenant pays the bill. In my own apartment I have an indirect tank as a zone on my cold start boiler year round. There's nowhere near the standby losses of a regular gas fired tank where heat is constantly going up the pipe from the internal exchangers. I have a programmable thermostat on it so I can use wide setpoints and it won't fire all day when no one is using not water.

                      If I had electric I'd simply blanket the crap out of a regular tank for very low losses. Supposedly now heat pump tanks are the way to go. Plus they'll dehumidify your basement at the same time!
                      Location: Jersey City NJ USA

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                      • #12
                        Wasn't a problem at all in my place. Summertime gas bills are definitely less. Everything but the water heater stayed the same. And I had a mega blanketed tank heater with insulated hot water piping previously. I also added a recirculation loop on a switched timer (tap the switch to turn on the recirc loop and fire the tankless heater - it shuts off automatically in 5 minutes unless you set it for longer) so that every faucet has got scalding hot water within about 5 seconds.

                        Although a tankless uses a lot of energy to heat the water rapidly, the newer ones are also WAY more efficient at putting all that energy into heating the water rather than sending it out the flue. Now if you're comparing to a piece of junk cheap inefficient tankless that's another story.
                        Last edited by eKretz; 05-28-2021, 11:53 PM.

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                        • #13
                          Tankless heaters are like everything else -- you get what you pay for. A good heater will output a consistent temperature regardless of input water temperature and total flow until you exceed its capacity.

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                          • #14
                            I would have an electrician check your wiring for loose connections. You may have a house fire in-the-making.



                            Originally posted by tlfamm View Post
                            My last electric tankless heater was a single-coil, 220 volt, 40-amp stainless vessel (a little larger than an oil filter) with adjustable temperature. In operation it would cause the lights in my house (and my neighbors) to flicker. Even after Boston Edison installed a dedicated transformer & pole for my house, the flickering did not stop. Problem was solved 5 months later when the unit failed.
                            Paul A.
                            SE Texas

                            And if you look REAL close at an analog signal,
                            You will find that it has discrete steps.

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                            • #15
                              I have a nat. gas 200,000 btu tankless heater that is a few years old. It heats the house through a brazed plate heat exchanger into a pex floor system and also heats domestic hot water. No problems so far. I got it from a big box store and so there will be little support if it breaks. The stepper motors are a bit noisy. Installation instructions need to be followed to the letter for warranty to be good.

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