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OT: tankless water heaters

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  • OT: tankless water heaters

    Anyone have any experience with these.

    After a little research it looks like the electric whole house ones require a very large energy demand when on, some quote a 300 amp house hold service requirement. Still cheaper then running one all the time but installation costs would be out off the question.

    Gas heaters look better, installation problems too, so we are getting an estimate.

    Has anyone any experience with these. What kind of problems have you had, like limited water availability, high gas usage etc.???? Maybe you think they are great. Would like to know before I get in to deep. Thanks.
    The shortest distance between two points is a circle of infinite diameter.

    Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

    Southwestern Ontario. Canada

  • #2
    I installed one in our addition, its a Bosch... I should have done it years ago. LP model, uses SCH 40 PVC pipe for exhaust, 10 yr warrantee, the thing is awesome.

    I have two teenage kids, 20-30 min showers are not uncommon, the thing keeps heating water until you run out of propane or run out of water. 250 gal propane tank lasts about a year.

    The model we have, has an electro-piezo ignition system, so it activated by the flow of water thru the heater, meaning with power outages we still have hot water.

    The only issues is that it takes a little time for the water to warm up.
    Mike Hunter

    www.mikehunterrestorations.com

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    • #3
      Six years ago I built a seasonal cabin for my kids on my remote isolated Northern Minnesota property.
      The only power we have is a 500 gallon tank of propane that runs the refrigerator, the stove, the heat and an 8 kW generator for lights, TV and the well pump.
      I also installed a propane fired tankless hot water heater. A Japanese Takagi.
      It worked fine until this year when it refused to light unless two faucets were open to make maximum water flow.
      There is a paddle wheel inside that detects water flow and lights the unit.
      I had to rig a hose to add vinegar to the unit to dissolve the lime deposits and free up the paddle wheel sensor. By the end of the season it had quit again.
      Next spring I am going to use a solution of CLR to clean out the gunk before I turn on the well.
      When I bought the heater it was the best in the market and one of the few. It cost $2500.
      Today there are several brands that operate on natural gas or propane.
      The electric tankless units do require very large currents and usually mean rewiring the house.
      Be careful what you buy.
      Bill
      Last edited by Seastar; 01-10-2014, 02:29 PM.
      I cut it off twice and it's still too short!

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      • #4
        I have friends who have gas fired tankless water heaters and they are generally happy with them. But all have found that professional servicing once a year is required.

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        • #5
          We put in a nat.gas Bosch a number of years ago and the only issue was that it required much larger gas inlet line than a regular heater. This might have changed now with current models.

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          • #6
            My wife and I live on Cape Cod. We have had a Rinnai Tankless Heater for 5 years. It is a natural gas model. There are just the two of us and we have been very happy with it. We set it at 115 deg F and the water is plenty hot for a shower and or a bath. Now for the negatives I have recently discovered. The vent leaves the house approximately 2 feet above the ground at about the same height as the High Efficiency Furnace vent. This is an area where snow drifts next to the house and you have to keep the vents clear or they both will shut off if snow blocks the vents. The tankless heater does require a sufficient supply of gas or it will groan and moan loudly and or shut itself off when it is asked to produce hot water at full capacity. Cutting down the flow of hot water needed will stop the noise. This only happens when the temperatures are cold as we have recently discovered. Like I say, we are happy with it, but if you are planning to install one make sure you have sufficient gas to run it. There are several FAQ sites about these heaters that will answer any questions you might have.

            Rick

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            • #7
              +1 on the yearly maintenance. They are efficient but you must keep them clean.
              My only complaint is that you (I) don't get hot water as fast. Maybe its just my plumbing, but we have to
              leave the faucet run probably a good 20 seconds before we get hot water.

              20 seconds maybe doesn't sound like a lot, but it gets tiresome. Other than that, no complaints.

              I'd suggest installing one 25-50% larger (BTU rating) than the handbooks suggest.

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              • #8
                I hate the things!
                They heat the water through a temperature range, not to a fixed temperature. The output temperature therefore depends on a) the input water temperature, and b) the water flow through the heater. So for the same flow the hot water will be cooler in winter than in summer; and if some one tries to wash the dishes while you're under the shower you will have a sense of humour failure. No doubt many people can cope with that, but it drove me nuts.
                Years ago I used to have an electric instant water heater for the shower, and it was hopeless.

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                • #9
                  Originally posted by Mike Burch View Post
                  I hate the things!
                  They heat the water through a temperature range, not to a fixed temperature. The output temperature therefore depends on a) the input water temperature, and b) the water flow through the heater. So for the same flow the hot water will be cooler in winter than in summer; and if some one tries to wash the dishes while you're under the shower you will have a sense of humour failure. No doubt many people can cope with that, but it drove me nuts.
                  Years ago I used to have an electric instant water heater for the shower, and it was hopeless.
                  The symptoms you mention are typical of a improper installation (gas piping too small/low pressure) or a unit that was sized too small for the house. They hold temperature very well due to a modulated gas valve with a typical range of 30-130000 btu depending on water flow and inlet temperature. I have installed many and also repaired quite a few with symptoms like you mention. It typically happens when someone does a DIY install and simply connects to the existing gas line from the old tank type heater (1/2 inch being common)

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                  • #10
                    Everything stated thus far is pretty accurate. They work very well. As for maintenance, the main thing is a inlet screen filter that has to be cleaned. If you are on well water or other that is very hard then buildups can become a problem. I installed quite a few for people and they worked well with no call backs. Many years back, I did my house first, with a Bosch unit.

                    For the original poster... They cost quite a bit fully installed because there is quite a bit of work to do it correctly. Gas supply is CRITICAL to proper operation. For example, Bosch devotes about half of their installation manual to the gas supply subject. The typical units high flame is 130000 btu or a much as 200000btu. If the gas supply is insufficient due to undersized piping, it cripples the units performance. They just do not tolerate pressure drop when the flame cranks up high.

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                    • #11
                      We have had a Rinnai for about 6 years. We love it. The plumber who installed it said he liked it better than the Bosch.
                      It just works. What more could you ask for.
                      Dave

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                      • #12
                        We install them in the buildings at work. LEED crap you know. Do they work better than a tank heater, no. re they mor efficient? Don't know. Would I buy one? Not a chance in hell. There is nothing wrong with the tried and true tank water heater. They don't require a yearly maintenance, they last for at least 10-15 years. You can install a simple timer if you want to cut power over night and/or during the day. No fuss no muss. Not a chance in hell..........

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                        • #13
                          We install them all the time only pre-determining factor is water quality. The harder the water the faster you will need the heater flushed out. I have some that are going on 11 years old never a call back. And some in 3 years. If you have a water softener that's a plus to life of the unit. Now as far as gas pipe size yes you will need bigger lines possibility. Some units go as big as 199,000btu. The new Navien heaters do not require bigger gas lines. They will run on the existing lines you have. There is something similar to a turbo fan in the gas system that pulls the required gas it needs.

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                          • #14
                            I forgot to add we see a large drop in gas usage when someone changes out a tank water heater to a propane tankless heater, over 200gal a year drop.
                            Last edited by jeremy13; 01-10-2014, 05:57 PM. Reason: spelling

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                            • #15
                              I should have added in the first post that I have a crawl space not a basement and I can't put a regular gas water heater down in it. Electrical costs here are ridiculous, that why I would like to go to gas.
                              The shortest distance between two points is a circle of infinite diameter.

                              Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

                              Southwestern Ontario. Canada

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