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Thread: Homemade induction water heater

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    Default Homemade induction water heater

    Inspired by the success of my I decided that the next summer could be coming in a few weeks and that is time to find something for those long camping trips.
    I did a lot of reading on the topic of induction heating to get my induction metal heater working and it is still a work in progress to get even more efficiency out of it.
    The good thing about all this reading is that you also get a better understanding on magnetism in general.

    So what is topic about?
    We all have hot water in our homes, some use gas, other electricty or even wood to heat it up.
    In areas with no gas mains supply or simply in your weekend home or camper you only have gas as an option.
    This is where "my" idea comes into place.
    I want to design a highly efficient water heater based on magnetic induction, similar to my other project but in "reverse".
    The benefit would be that the actual heating unit can be sized to your actual needs and what is available in terms of electricity supply.

    How do I think it should work?
    Well, my "studies" showed that heat from induction needs high frequencies and strong magnetic fields to work.
    I don't want to into all the details about magnetic fields, windings and resonance so for that check the link above to see what I could gather so far.
    If you move a magnetic field over a conductor the resulting field changes will induce a current flow in the conductor - this current, if strong enough, will heat the conductor over time.
    This idea started a few months back when a friend ran out of hot water because his gas bottle was empty again - not very efficient these cheap camping hot water systems...
    So forgive me for not taking a video of my test but you can replay it at home:
    Take a fast router that can go to at aleast 10.000rpm.
    Take an old router bit and mount a strong neodymium magnet with epoxy glue centered on the bit so the poles face outwards to the spindle at 90.
    Mount the router with the bit so it face upwards (does not matter but makes the rest easier) - be sure it is tight and won't move around when you start the damn thing!
    Create a mounting plate that can be fixed or clamped to the no upwards facing base of the router.
    In the centre mount a piece of pipe - I had a 40mm copper pipe that only left about 2mm gap to the two magnets I joined together.
    Make sure the pipe is properly centered around the router bit and fixed in place!!
    If can vary the speed of the router start at the lowest and work your way up for a nice effect
    You will see that within a very short time the pipe get hot, in fact red hot if you don't turn the router off or cool it!

    What is the aim here?
    To find a simple, yet efficient design that can be mounted or connected to basically any motor with a reasonable speed.
    For camping use I was thinking of the motors for fuel pumps as they are strong and quite fast, plus they don't mind continious use - but does not matter as long as it fast.
    I want to find and tests ways of making such a system efficient enough to be used as a continous hot water system with enough power that a good shower is possible.

    Current design idea:
    In the most simple form a stack of neodymium magnets on an axle, the magnets should be twisted so a spiral forms with opposing poles next to each other.
    As an alternative the rotor of a DC generator or motor can be used but it should be the types with two rings for the connection, not the standard slotted design.
    The actual generator needs to be able to accomodate the cooling, for us the water we actually want to heat
    It also has to be able to get a huge current induced by the magnets while at the same time be low on mass with a high resistance to the eddy currents we want to induce - that why it is an induction water heater
    Have to go a bit deeper here so get an idea how the system works - sorry...
    Using a metal pipe around the magnets (will call the whole thing "rotor" from now on!) will heat it up nicely but is not efficient if we want water going through.
    Several designs you can find on the net use quite complicated spheres of copper pipe, formed as a coil, around this centre pipe.
    To keep the heat some enclose the whole thing with copper sheets - not very smart if you ask me as there is no benefit for the magnetic field and the copper trensmits the heat to the outside, insulation would be smarter...
    But what if we actually create an inline heating system?
    The rotor creates massive field lines in the pipe wich not only alternate by the spin but also by the placement of the magnets itself.
    Using a coil type water circulation system that actually works would require to match the pitch of the copper coil to the pitch of the rotor and trust me you either need very small magnets or end up with a "bird cage" of copper pipes.
    Keep in mind the produced magnetic field would rotate around the axis of the pipe any other way and it can't work.
    To simplify the design of a heater core I was thinking of a relatively long rotor and pipe without copper pipes brazed onto the surface.
    Instead I would use a second pipe, perferable something heat resistant but thermally insulating, that only leaves a small gap to the copper pipe around the rotor.
    Capped at both ends and with added water connections on the end plates or outer pipe it should work fine.
    To further improve efficiency there should be a spiral between the pipes, best from copper and brazed to the inner pipe.
    This way the water has longer way to travel and more surface area for the heating at the same time.
    Of course there need to be either a bearing on the end of the pipe for the rotor or both heater core and motor/rotor assembly must be properly fixed - keep in mind the rotor needs to be balanced to avoid vibration and damage to the bearings.
    It needs to be tested if a magnetically inert material for the outer pipe works better than a galvanised pipe from soft steel - I am uncertain if a magnetic outer core that is not made from ferrite would work for those high frequencies as in my test the penetration trough the copper goes down the higher the speed of the rotor is - high frequency induction inside the pipe from the opposing magnetic fields generated by the rotor, at high speeds these magnetic fields start to cancel each other out in favour of the low electrical resistance of the copper and produce elecricity which adds to the already generated electricty from the rotor itself.
    Find the right speed for the magnet configuration and just a copper pipe is glowing red in under 2 minutes!

    My problems:
    I only have a quite thin copper pipe or a 80mm pipe at hand.
    For the thin one I have some magnets left for a small scale test setup but the big one would require a suitable DC core or at least a few hundred magnets, not to mention the problem of centrifugal forces on the magnets at high speeds and the safety concerns if the glue gives up (never use without water for the cooling LOL).

    I hope someone finds interest in my design ideas and tries something out, I won't be starting building this project until my other one is performing to my satisfaction.
    In my test I used a 50mm copper pipe, about 15cm long with a few rounds of 1/4"" copper pipe coil brazed onto it.
    No external pipe or insulation.
    Rotor was a router bit with two big magnets glued onto the top, I centered the bit in a cardboard pipe and filled it with resin to make sure the magnets are fully enlosed.
    With low pressure a glass of water was filled in about 20 seconds and the temp difference was a bit over 18
    Considering only two magnets were used and that they only covered 5cm of the pipe it was quite good.
    So a longer rotor with more magnets that cover the full lenght of the pipe enough flow and temp should be possible for a good shower.
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    I have one problem with this.
    The loss you have when driving the electric motor and then the second energy conversion of producing the heat with magnetic induction will be higher than using the same amount of electrical energy to directly heat the water with a plain resistor wire.
    This era of thoughtless consumption must end so we can encourage a world of creative geniuses rather than consumer idiots.


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    You should try some strong magnets on a fast motor first, you don't need a 1KW motor for this
    And if there is any resistor (or heating coil) that does it more efficient be my guest.
    The aim is to provide an alternative that can be used on a small scale with no problems and does not require maintenance except the motor.
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    Yes you do. To produce 1kW of heat you will need quite a bit more than 1kW using a motor due to the losses.
    You can heat the water slower if you want with less power but the losses will be higher. Heating slower reduces efficiency as more heat is lost to the environment while you are waiting for enough water to get hot.

    The most efficent way to heat water is in a very thin vessel surrounded by vacuum with a resistor immersed into it.
    But the good old fashioned boiler jugs are not too bad at it either.
    Micro waves are the next best because you are only heating the water, not any copper pipe or motors , but the transformer and magnetron has losses.
    I don't see a very efficient coupling of energy by swiping a magnet over a copper pipe to induce an eddy current.
    Last edited by Uncle Fester; 18-05-14 at 05:25 PM.
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    I really like the idea that you are experimenting with these things but rather than re inventing the wheel, how about having a look at what this guy did with radio waves and water for some alternative ideas.



    Of course I tried a little medicine cup with salt water but got no flames
    No idea what frequency he was using

    This would not generate energy but it converts it.
    It would be nice if it could dissociate water more efficiently than just poking some electrodes in the water using PV solar panels.
    Last edited by Uncle Fester; 18-05-14 at 05:39 PM.
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    The idea of radio waves is not new, same for ultrasonic frequencies that makes water illuminate.
    But a bit hard to do at home, at least for me.
    Not easy to find something with proper measurements, so this video has to do for now:



    Less data but wroking to heat oil:


    I think with tiny gaps and a proper design it should be much efficient.
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    Video 1:
    I would say the results from our induction heaters are far better. We both can achieve temperatures of well over 1000 ˚C in a matter of seconds and I am only using 150W of electrical energy even with the bad caps and unshielded coil(I want to wait until the better caps and FETs arrive before I build the second one with Litz). How hot is gets says nothing about the energy it is producing. We would need to know how long it takes to heat a cup of water from 20˚C to 100˚C at measured consumption.

    Video 2:
    Unfortunately does not mention how long it was running and how many watts his rather large and noisy motor is consuming to heat what I am guessing could be 100-200ml oil.
    I am having fun imagining using this on a camping site to make a cuppa, definitely good to get a lot of attention if that is your kind of thing
    … also carting it around in the bush in my back pack sounds like fun. Nah I will stick to my little spirit cooker that fits in my pocket until somebody invents a cigarette packet sized super capacitor that can store 1kW/h for my "Reisetauchsieder"
    Last edited by Uncle Fester; 18-05-14 at 08:48 PM.
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    We heat ferrous metal with an magnetic field we generate.
    The magnet system is a bit different.
    Give me some time and I will put up a little prototype for some proper measurements.
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    I do not have near the skills as you when it comes to these water heaters, but I am very very interested. I live west of Brisbane.
    In the early 1990's, I had some experience with the magnetic air heaters, specifically the Gerard Magnetic Thermal Energy Systems. It was clear to me then of the vast potential of the magnets.

    How have you progressed on you induction magnetic water heater? I am very interested.
    Currently I have an inefficient on-demand Rinnai B24 gas hot water heater, and I am looking to replace it with something "outside the norm".

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    Unfortunately Downunder has left this forum.
    We messed around with this stuff for fun, actual practical use was very distant.

    There is only one sensible and practical way to heat water and that is directly with the sun where all our energy came from even fossil fuel. Everything else is secondary.

    I do something outside of the norm in that aspect for over 10 years now. I have a lot of rubber tube mat that was originally intended for pool heating (but is also food grade available) lying on my roof. It fills old HWS tanks, about 500l. The system is not pressurised. A simple 24V solar pump keeps it flowing and when I need water a solenoid valve open mains water into the bottom of the tanks and pushes it to the open shower head.
    Unlike expensive solar hot water panels it can not be damaged by hail.
    There might be 3 days in the year in winter when the sun didn't shine at all and it rained for 3 days in a row where I might have to skip a shower. 1 hour of sun is all I need to heat the smaller tank which is good for 4 showers.
    I believe essential for this to work even under cloud are dark roof tiles that absorb infrared. Even if the air temp is 20˚C under whole day cloud I get over 35˚C water. Rain and wind is a hassle but when does it rain in this county?
    Last edited by Uncle Fester; 16-10-19 at 09:19 PM.
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    Peter 66 welcome to the forum.

    There is a special section for new members to introduce themselves at .

    Unfortunately, you've revived a thread that is five and a half years old.

    A quick search of the forums indicates that member, Downunder35m doesn't appear to have posted since his post immediately above yours.

    It would be best if you created a new topic as concept of heating water using magnetism seems like a very interesting subject to pursue further.

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    Default Gerard Magnetic Heat Units

    Fester, Brilliant, cheap and inexpensive. I love it.

    You may be interested in this, and it is relatively simple to build. I was involved with them some time back. There are still working units in Maryland USA. I have all of the documents (patents, schematics, test results and more) here with me in Brisbane.

    If you can access US Patents look for:
    Inventor Frank Gerard

    5,012,060 Permanent Magnet Thermal Generator Inventor Frank Gerard
    4,614,853 Permanent Magnet Steam Generator
    4,511,777 Permanent Magnet Thermal Energy System

    The Magnetic Heater Model MH-300 was tested May 1993 by MET Laboratories, Inc.
    The efficiency results came back as follows:
    13-May-93 101.57 %
    13-May-93 106.85 %
    13-May-93 106.84 %
    13-May-93 112.53 %
    13-May-93 115.86 %
    13-May-93 123.43 %

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    Is this it?


    Looks like it would be redundant compared to a recent heat pump system IMHO

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    Yes, it appears that is one of his US Patents.
    You may be right Skepticist. I hope you are right!
    Science had made great advancements since the 1980's and early 1990's. If modern heat pumps can provide efficiencies of 100+% then it would appear you are correct. I would love to see more on the heat pump system IMHO. Can you provide me with a link?

    Little history: So, as I know it, Frank had a background in physics, but it was all interrupted by WWII. After the war he took a job as mechanic/mechanical engineer with Pepsi Co. and that is where he remained until retirement. Upon developing his magnetic heat systems, Frank was in contractual and licensing negotiations with General Motors and other large firms. Unfortunately, the corporate sales, negotiation and contractual world was not in Frank's comfort zone and eventually led to 3-4 heart attacks and ultimately his death. We've all seen this before whereas great minds, because they are some emotionally involved with the inventions, try to manage all aspects of control in bringing a product to market but fail. Hence, great technology remains stagnant for decades.

    Just a interesting note: At one point, and this is not documented, we were tweaking the "blower" type magnetic heater, we fitted a metal shroud/tube to the output heated air which had increased to to appox. 90 F, and redirected only 10% of this air back to the input access. This caused the output air temperature to increase exponentially to approx. 400F and still climbing, but we shut it down for safety reasons. Normally the output air temperature would reach a plateau and remain constant. Also, there was no change in energy consumption.
    Just some food for thought...


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    You need to look at it from an economy & practicality angle.
    Modern heat pumps for heating water use a fraction of the electrical energy (like ~20% or less) compared to a conventional electric storage water heater and overall are about 3x the efficiency. The downside is they are much more expensive (like 3x or more currently) than a standard water heater and relatively noisy in operation so an outdoor enclosure may be needed.

    When I looked at them some years ago it only looked practical for something larger than a typical household like camping area amenities blocks or similar.

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    Many heat pump water heaters have had reliability issues.

    I have a mate that does AC for industrial and commercial applications as well as pool heating for councils etc.
    He wouldn't have a Heat pump as a gift and he's the guy that fixes them. Weekly in most cases.

    The lower running costs are not made up for the problems many of the things have. He says it's all the luck of the draw how the things go but he has yet to put a second one in anywhere that had them previously. I think that says something.

    IMHO people would be better to spend the money on solar PV if they don't already have it than the extra expense of a heat pump.
    If they do already have solar then a heat pump efficiency is less important anyway.

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    Moving mechanical parts like motors & pumps are always a weakness.

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    Quote Originally Posted by Skepticist View Post
    Moving mechanical parts like motors & pumps are always a weakness.
    That's a good and Valid Point!


    As my mate says, not much to swapping out an electric element. Can take longer to get into the thing on a heat pump than swapping an element or a thermostat and the second the heat pump needs a part, there goes your power savings.

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