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Thread: Passive water heating

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    Default Passive water heating

    hi, yes I'm new

    my hot water tank started leaking (corrosion) so I replaced my whole solar system - short story the heat exchange panels were made by another company and the company replacing the water heater tank refused to give me a warranty if I used the existing heat exchanging panels so I replaced the lot (tank + panels)

    I'm keen to use the old heat exchange panels (which I kept on the roof) to do passive underfloor (water) heating.

    I haven't been find much information about this on the web - has anyone done this, does anyone know anyone who might have installed something like this?

    Ideally I'd like to passively heat water/glycol under a floating floor in my living room with some extra heat exchange from my wood heater if possible with maybe a solar powered pump to circulate the water if possible, should be a very cheap way to raise the temperature of my living room in the winter

    cheers

    Jason



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    Obviously you must use a pump as Hot Water Rises and there is no way it will come down from the roof to floor level.
    I would suggest you put any pump at the end of the run before the water returns to the panels and get a metal body pump seperated from the motor if possible.
    The reason is that the plastic pumps I looked at had temp ratings (if any) of around 64C and while I doubt the water would get that hot, but you never know.
    I put a small pump on a donkey hot water system because I was loosing flow to the shower but I had no choice other than to put the pump right at the storage tank but for central heating, the pump works better when its at the end of the run because the water is cooler and oddly enough, pumps better according to an Army Manual I have on pumping liquids.
    Also the motor doesnt get overheated as they are generaly enclosed to be used around water etc.
    Due to a bit of enthusiastic over banking, I have blown steam out of the taps so had I used a plastic body pump, it most likely would have over time warped it beyond use.
    you will have to investigate if your going to pressurise the system or have it ventilated as hot water expands and steam destroys, sometimes fataly.
    I remember a home made Donkey system over pressurised and blew a concrete wall down and killed one or 2 who where in a shower area next to the system.
    For pumps, have a look at marine bildge designed ones as they can be cheap and run on low voltage from what I have read.
    Unfortunately my old Donkey split the tank and I havent been able to repair it yet so I went to a small Gas fired Instant unit which works damn well.
    Last edited by gordon_s1942; 19-12-10 at 03:05 PM.
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    thanks for that
    I was thinking a glycol/water header expansion tank with pressure relief would be the go
    thanks for the advice about the pump also

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    Quote Originally Posted by gordon_s1942 View Post
    The reason is that the plastic pumps I looked at had temp ratings (if any) of around 64C and while I doubt the water would get that hot, but you never know.

    Due to a bit of enthusiastic over banking, I have blown steam out of the taps so had I used a plastic body pump, it most likely would have over time warped it beyond use.
    you will have to investigate if your going to pressurise the system or have it ventilated as hot water expands and steam destroys, sometimes fataly.
    I remember a home made Donkey system over pressurised and blew a concrete wall down and killed one or 2 who where in a shower area next to the system.

    For pumps, have a look at marine bildge designed ones as they can be cheap and run on low voltage from what I have read.
    Ok, 1. Solar Panels and temperature.
    The very nature of solar energy is such that solar hot water systems are termed as 'uncontrolled heat sources'. They will definately get hotter than 64 degrees, they most certainly have the potential to boil - hence steam - hence lots of pressure - hence very real possibility of large explosion.

    2. I am guessing an ideal example of why Plumbing is a protected trade.

    3. I am doubting marine pumps would handle the water temperature or the hours of pumping required to keep heat in the floor, they would be designed more for short pumping periods.

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    Quote Originally Posted by JasonC View Post
    my hot water tank started leaking (corrosion) so I replaced my whole solar system - short story the heat exchange panels were made by another company and the company replacing the water heater tank refused to give me a warranty if I used the existing heat exchanging panels so I replaced the lot (tank + panels)

    I'm keen to use the old heat exchange panels (which I kept on the roof) to do passive underfloor (water) heating.

    Ideally I'd like to passively heat water/glycol under a floating floor in my living room with some extra heat exchange from my wood heater if possible with maybe a solar powered pump to circulate the water if possible, should be a very cheap way to raise the temperature of my living room in the winter

    cheers

    Jason
    Considering the original tank corroded away I would not be surprised if the panels are far behind it. What ran through the panels previously as some are designed only to have water in them, some only for anti freeze/rust solution, we would need to know what type of system it was.

    Once it is working it probably would be cheap(ish) to operate but will cost a packet to install.

    Something to think about - if you want to heat your floor, I would imagine during winter because thats when it is cold and using solar panels which will only work efficiently in weather when it isn't cold (e.g. summer). Lot of money to set up something to heat the house in summer.

    The wood fire only creates more issues.

    Good in theory but.......

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    There is no simple solution to anything is there?
    One thing I didnt mention regarding the Donkey is it is a coal burner and untill recently coal was fairly cheap to the extent it cost me about a $1 a week to run the donkey BUT recently coal price has increased dramaticaly from $70 a truck load to over $400, I kid you NOT !!
    Pressure valves are ok but they waste water as it runs off when they open so you need a means to replenish the system same as your cars radiator.
    I regreatably have to agree with Sandgropers final comment that it is Good in Theory BUT !!!
    If we could afford to do all these things, we could live in an area where the Temperature doesnt vary by more than 10 C Day and Night all year round, as if !!!
    I stand unequivicably behind everything I say , I just dont ever remember saying it !!

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    but it must be able to be done - the theory is good !
    water flows through piping under floor, heats floor, room gets less cold
    in summer you stop the water flow, shut the system down etc

    does it need to be that complicated?
    I'm just trying to understand why this shouldn't be fairly simple in design?

    regards

    Jason

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    Not complicated (with the right knowledge)
    I guess the inherent problem with this one is the panels are not designed for what you want to do with them.
    As I mentioned, solar is an uncontrolled heat source, be very very carefull.

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    plumbers install those anti scalding valves on solar hot water systems so I assume you could put one of those in line to drop the temperature down, I'm sure this can be done

    some other info here

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    Solar panels HEAT during the Day and contain the water in a well insulated tank, here your taking that hot water from the tank down to the floor where you take the heat OUT of the water and return the COOLED water to the panels which at NIGHT, dont get hot !!!
    Look at how the heater in car operates, Motor running (Sunshine) nice warm air into the car but turn the motor OFF (NIGHT TIME) the heat would drop off even if you kept the water circulating !!
    Remember your circulating this water to heat the floor CONTINUOUSLY, not just drawing off as you would do with a domestic HWS so I would think in less than a few hours without some sort of heating booster, the water temp would drop to around the ambient temp even if it was insulated perfectly.
    Another problem that Hot water systems have is the lag between raising the temp and dropping it.
    As for anti scalding thats only for Baths and Showers, you want MAXIMUM heat in the pipes as they shed their heat into the air in the room to heat it.
    Thats why you see the pipes covered and the radiators enclosed to keep from being touched.
    And no matter how perfect your system is or what liquid is used, it needs 'topping up' at intervals just the same as a car's cooling sytem.
    Last edited by gordon_s1942; 20-12-10 at 04:00 PM.
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    so when water tank temp > inside temp, pump runs
    when water temp < inside temp, pump not running

    on new inventors (ABC) :

    Technically, Solar Floor Heating uses the hydronic (i.e. liquid) system of solar power to radiate heat through the floors of the building using solar heated water from an accumulator (i.e. water storage tank.) This can be linked to a swimming pool and/or spa, if you have one.

    In simple terms, Solar Floor Heating works by capturing solar energy from rooftop collectors traditionally used in solar pool heating. Solar pool heating collectors are usually mounted on a roof surface facing the sun.

    The collector consists of specially designed plastic polymer or rubber strip with moulded tubes for carrying water. These strips are usually laid out side by side in a sunny location and connected to the pool via larger PVC pipes. While black solar collectors will always be the highest performing product of any solar pool heating system, coloured solar collectors are becoming more popular when aesthetics is of absolute importance.

    When the pool water is pumped through the strip, the water absorbs solar heat energy and transfers it though to the swimming pool.

    However, because of the significant volume of water needed to be heated in a swimming pool, the water temperature seldom exceeds 18 degrees Celsius in a heated pool, a temperature which cannot provide sufficient warmth to heat a building. The inventor of the Solar Floor Heating system has solved this problem by pumping the partially heated swimming pool water to the accumulator (or storage tank) where solar heat can be concentrated to heat the water to 38 degrees.

    That water is then pumped through an underfloor system of heat panels or dispersers which are placed between the floor joists or in a concrete slab. Once the storage tank is filled, the swimming pool itself, as stated above, becomes redundant in the system.

    For those who do not have a swimming pool to provide a water source, the accumulator alone is sufficient to store and provide the water needed to fuel the solar heat.

    Within the system, there are switches or isolation solenoids which enable the heating of specific rooms or parts of the building. Solenoid is a current-carrying coil of wire that acts like a magnet when a current passes through it”

    A return/diversion valve enables you to send the semi-heated water back to the solar collector on the roof or, more importantly, back to the pool or spa providing home heating ,and heated pool and spa in one through the winter.

    The system can even be used to cool the house down in summer simply by switching it on at night and letting the cool pool water circulate through the underfloor system.

    When the system is turned off, an air valve on the roof manifolds (standard on all solar pool heating systems) allows the water to drain out of the system. This prevents water from freezing and damaging control panels. Manifolds are pipe fitting with several lateral outlets for connecting one pipe with others.

    Another feature of the system is an automatic temperature controller which senses when heat is available and when this happens water is circulated through the system until a temperature drop is sensed and automatically closes down the pump or opens a bypass valve to recirculate stored heat to the underfloor panels only.
    Last edited by JasonC; 20-12-10 at 06:31 PM.

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    Quote Originally Posted by JasonC View Post
    but it must be able to be done - the theory is good !
    water flows through piping under floor, heats floor, room gets less cold
    in summer you stop the water flow, shut the system down etc

    does it need to be that complicated?
    I'm just trying to understand why this shouldn't be fairly simple in design?

    regards

    Jason
    Hi Jason,
    Just wondering whether you ever solved this? I'm hoping to install underfloor heating with glycol as the heat transfer liquid, using an open wood fire as hest source. I agree the therory is good, but can't find any technical solutions.

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    What annoys me is in that in the Northen hemisphere, countries like the UK, USA and Canada use various systems for radiant heating but here when you ask or try to find any, they all look blankly at you, same as 'Double Glazing' of windows, errrrr whats that and why do you want it ?
    You see on those UK renovation shows a 'boiler' of about the size of a small clothes dryer, possibly 45 litre (10 Gal) size running radiators for heat and they have it a bloody sight colder for longer periods than even the Snow Mountains has.

    The other problem is very few houses, even the \very latest are properly insulated.
    R5 is considered the max here where others go as high as R35 which I ask why dont we?
    Insulation works BOTH ways, keeps the heat in during winter and the heat out in Summer.
    Finding a suitable heat source and getting the water to flow to me are the two main requirements of any system as well as ensuring you dont blow your self up when its running.
    I stand unequivicably behind everything I say , I just dont ever remember saying it !!

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    I know
    I gave up on the idea of passive heating - I couldn't get any advice or even find the parts to set it up

    also double glazing is largely a novelty in Australia which seems weird to me as well

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    obviously the task you have done is not supported the warranty issue of your solar system. You will only get the warranty service when you don't repair the tank from anywhere else.

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