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Magnetic Induction Combi Boiler?

Andrew Hagen_2
Andrew Hagen_2 Member Posts: 236
I feel a tank is the way to go with domestic hot water heating. Most DHW loads are intermittent, relatively high heat load, and short in duration. In my opinion, these characteristics point toward a well-insulated tank-type water heater being the ideal setup.

Electricity is generally a very valuable and wasteful form of energy, having a few characteristics that make it useful for small loads where other forms of energy cannot be used. For instance, it would be difficult to power your computer directly with natural gas.

Gas, oil, and solar energy are the most appropriate for heating, as I see things. Electricity should only be used where no other form of energy will do the job.


  • Antony Upward
    Antony Upward Member Posts: 11
    Domestic Magnetic Induction Combi Boiler?


    Sometime ago I installed a gas NTI Trinity Combi boiler / on-demand tankless DHW solution...which is great. This drives an underfloor system for the basement and an airhandler for the rest of the house. At the time it was the most energy efficient solution and energy star compliant.

    But with all the talk of greenhouse gases...got me thinking about whether there was a zero (at the house) emmissions alternative.

    Electric is clearly the way to go...assuming you are generating or buying zero emmissions generated electricity (solar, wind, and less so water)

    Typically electric systems can't do the on-demand DHW - and need a tank (which I don't have space for). I believe this is because it takes too long for an electrical heating element to get hot enough.

    But...there is another form of electrical heating which is commonly used in kitchens...professional (and more commonly in Europe domestically). Its called magnetic induction. Check out http://www.cooktek.com/induction.html for an overview.

    We have one of cooktek's single "burner" units and it is incredibly fast...much faster than gas or an classic electric immersion kettle at boiling water.

    As far as I can tell (and I'm no expert) the whole of the bottom of the kettle gets hot almost instantaneously.

    So this got me thinking...could this technology be used to produce a domestic magnetic induction combi boiler...to replace my NTI Trinity?

    I did a few google searches...but all the induction boilers out there seem to be industrial.

    Anyone know if this exists...or is this a product waiting to happen?


  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928

    Magnetic inductions cooktops (they've been around for well over a decade) only work with iron-containing pots/pans. Your kettle gets hot so fast because there's no "burner" and it's the kettle itself that gets hot.

    Immersion-type electric heaters (like used in boilers and water heaters) are surrounded by water so every BTU gets transferred to the water the only losses being in storage and transmission. Heating via magnetic induction may also be a "lossless" method, but I'm not sure. The only real advantage I could see to magnetic induction for water heating is that there are no elements to burn out--often due to scale-induced overheating of the element.

    I don't know if this is true for other boilers with a stainless steel HX, but I just checked my Vitodens (and indirect) and the stainless steel alloy used (SA316Ti) is non-magnetic (I checked with a VERY powerful rare-earth magnet) and might not be usable for magnetic induction heating.
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928

    Just did some Googling and at least for magnetic induction cooktops, the efficiency is 84%. Significantly better than a gas cooktop but far below an immersion electric heater (100%) and well below good gas mod-cons in most conditions as well...

    Also specifically mentioned that the cookware MUST be magnetic. Attempts are being made to overcome this limitation, but efficiency is a HUGE obstacle. The simple test for cookware used on a magnetic induction cooktop is "Does a magnet stick?" so that would tend to tell me that the most durable stainless steel alloys (that tend to be non-magnetic) would not be suitable.

    In theory at least, magnetic induction could modulate down "to the heat of a match", but it's still electric which is in most cases is the most costly form of heating.

  • Perry_3
    Perry_3 Member Posts: 498
    The problem with instantanius electric heat..

    is not that the element can scale up...

    It's that you can't draw enough current to do the job in a tankless scenerio for most houses.

    Magnetic induction, or even direct current warming will still have this problem.

    But, at least you are thinking outside of the box.

  • singh
    singh Member Posts: 866
    No problems

    With my instantaneous eletric heat unit. Over seven years now. I have enough "draw" and can take endless showers. (If I wanted to, but that's wasteful.)

    I have a scale stopper cartidge,which I recommend before all hot water heating devices. I check the elements once in awhile, clear as a bell.

    In a few short weeks, I'll be installing a evacuated tube solar collector on the side of my house to pre-heat my tankless or on really sunny days , no call from the heater at all. It's a Microtherm Inc. heater.

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