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Instant hot water

hanlonk | Posted in Construction Techniques on October 20, 2002 07:03am

Can anyone give me some insight on point of use electric hot water hesaters? I need to heat water for a sink and shower in a backyard cottage. What size piping? What wattage? etc. What degree rise for what flow rate? If someone has done the homework I’d appreciate a holler.

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  1. fredsmart48 | Oct 21, 2002 12:14am | #1

    The only difference that I can see between the 1500w and the 3500w electric water heater is the 3500w recovers faster. There is a thermostat that shuts off the heating elements when it reaches 130 degs. or to what ever you set it for. It should not cost any more to run a 3500w then the 1500w because the 3500w is not on as long as the 1500w.

    The cost difference of replacement elements 1500w and the 3500w is 4 to 5 dollars. So the cost difference between the 1500w and the 3500w should not great for that reason. You want a glass lined tank, that may be a reason for more cost. Glass lined tank will last longer.

    The difference of the cost of the wire between the 12 gage and 10 gage is small also. You just need a heavier breaker in the power panel.

    When you plumb it don’t mix metals. Don’t use brass and steel. Don’t use copper with steel. It causes electrolysis and the joints fail in time.

    1. hanlonk | Oct 21, 2002 04:35am | #2

      yo Fred thanks for the reply but I'm looking for info on INSTANT hot water heaters, i.e. tankless.

  2. bake | Oct 21, 2002 07:14am | #3

    There has been much debate over these water heaters, try the search function and I am sure you will come up with lots of reading.

  3. dabonds | Oct 21, 2002 05:43pm | #4

    It depends on several variables. I live in New Orleans where the tap water never really gets very cold. If you live somewhere where the tap water gets ice cold in winter you will need more power to get that water up to shower temperatures. Don't worry about the technology. These types of heaters have been used in Europe for more than 20 years. I have seen a system that can be home made if you are familiar with temperature controllers and power handling. I saw a system where the guy just went and bought several (in this case 4) electric water heater elements and mounted them into copper wells that he made up from fittings in series. They come on as soon as the flow starts (you need a flow switch) and by the time the water exits the fourth heater it is hot. This setup was for a whole house so you would not need 4 but I like the idea. If an element fails you still get some heat. The elements are cheap, easy to get and easy to replace. You would need to do the math to get the power right but its easy if you know your electricity.

  4. Bruce | Oct 23, 2002 07:26am | #5

    Go here

    http://www.dulley.com/search.shtml

    and enter "tankless water heater" in the search box.

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