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electric heater as storage tank

I have an older boiler with tankless coil, I can't get enough hot water to fill my tub.  I was given a month old electric hot water heater. How would I install this as a storage tank to give me more hot water?  I Can't let this boiler go cold, Thank You for any help, any diagrams out there? Thank you,,,  cold up here in Maine


  • billtwocase
    billtwocase Member Posts: 2,385
    2 options

    either use it strictly as an electric water heater, and set your low limit to 100 degrees, or have it installed as an aquabank. You will need a domestic circulator, disable the heating elements, and tie the circ thru the bottom thermostat on the tank. The boiler should maintain at least 150 degrees if you go this way. A good electrician can do this no prob
  • Paul48
    Paul48 Member Posts: 4,469

    a few years,I fed through the coil in my oil-fired boiler to a gas hot water heater.My gas bill was about $15 a month with cooking included. In other words, the gas water heater didn't fire often at all. If you have the power available, I'd wire it up, and give it a shot that way. I know gas is different, but we could take 7 showers, back to back, while washing clothes and never run out of hot water.
  • icesailor
    icesailor Member Posts: 7,265
    Electric Storage Tanks:

    I've done this for over 40 years. I have had them in every home I built and owned. I have one in the home I am in now.

    I pipe the water heater like it is a stand alone water heater, change the bottom drain and put a tee and drain, install a Taco 006B bronze threaded circulator so I can use brass nipples, and pipe that to the cold water inlet of the tank less heater. The hot water outlet connects to the top of the electric water heater tank at the cold water inlet. The dip tube takes the heater water to the lower 2/3's of the tank. You do not connect the heater to any 240 volt wiring. Disconnect ant wiring in the tank from the bottom thermostat and use that thermostat as a switch to run the circulator. You can run the circulator with a cord whip like some stand alone "aqua-boosters" do. You do not need to get into the boiler controls. Set the boiler control to 20 degrees above the operating temperature. Set the operating control to 140 degrees to stop condensation. I set the high limit to 160 to 170 degrees.

    The "indirect coil", the Tankless coil, is no different that the "Indirect Coil" in an indirect water heater. And a lot cheaper if you already have a boiler with a tankless coil installed. There are no complicated boiler water piping and electrical issues.

    It's so simple that it is stupid.

    I had four teenagers grow up with a 50 gallon electric water heater storage tank. We never ran out of hot water. The same that I have right now.
  • Zeffern_Cochrane
    Zeffern_Cochrane Member Posts: 12
    Icesailor you lost me

    When you say "The hot water outlet connects to the top of the electric water heater tank at the cold water inlet." i started getting lost. But I did understand enough of this post to recognize that potentially this could be the best idea yet to smooth out the peaks in hot water usage from a combi boiler.

    Also I have seen a few posts regarding how using a combi boiler to heat hot water in during the non heating months may not be the most efficient way to generate DHW

    I'm looking for ideas for my new home build. Over the years I have been collecting junk like a hoarder. I currently have an old 25Gal electric tank as well as a new 50Gal gas hot water tank (Got them both for free :) Somewhere i read that you had a diagram of this setup could you steer me towards that please.

    Any opinion on setting up something that utilizes the Gas HWT in this kind of setup and making it functional for the non heating season?

    Another consideration is that I have a copper drain heat recovery unit installed in my new house.

    I am starting to think that I could utilize a $200 brazed plate exchanger and circulator to warm up water in the hot water tank. and if the water temp started to drop to much the gas burner on the water tank could kick in if required.

  • moey
    moey Member Posts: 40
    do the math

    Depending on where you are in Maine its probably cheaper to use it as a electric hot water heater then run your boiler to make hot water. Sign up for a new supplier in Maine if you have not already it will knock off half cent to cent per kw/hr off your bill. My electric hot water tank costs me about $35 a month to operate in Maine. Family of 4.
  • Zeffern_Cochrane
    Zeffern_Cochrane Member Posts: 12
    Electric is probably out of the picture

    I am in Alberta Canada here by the time your finished paying for the electricity, distribution of electricity and the upgrade the grid charge for the POOR electric company that can't afford to maintain there own infrastructure your paying about 20-25 cents a KW

    Consequently were pretty big fans of clean burning natural gas up here. :)
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