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Solar water heating and household appliances

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  • 08-02-2008 8:16pm
    #1
    MickLimk
    Closed Accounts Posts: 188 ✭✭


    Started this discussion in another unrelated thread but wanted to ask some broader questions:

    With solar water heating, it is very possible to be in a situation where you have more hot water than you actually require at times. In my mind, a most efficient use of this 'free' hot water would be to use it in household appliances that usually heat their own water, eg. washing machine, dishwasher.

    However, in a previous thread (thanks Builderwoman, Knighted!), it's been pointed out that a lot of washing machines only have a cold inlet and even those that do have both hot and cold, only take water from the hot when the wash program is 60C or greater.

    My many questions:
    1. Does anyone who has solar water heating run the hot water to their appliances and does it make a difference?
    2. Can you run hot water only to a dishwasher given that it almost always heats the water to 50C or greater (except on rinse cycles)?
    3. Are there any washing machines that have thermostatic mixing valves on the water inputs that allow them to use hot water for washes <60C?
    4. Is there any point in fitting a thermostatic mixing valve from the hot & cold supplies into a washing machine cold feed? Obviously the temperature here would generally need to be fixed at about 30C or so to prevent damage to clothes.
    5. Are all my questions a complete waste of time and not going to save any water heating costs anyway!?

    All comments welcome!

    Thanks,
    Mick


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    #2
    Alun
    Registered Users Posts: 21,470 ✭✭✭✭Alun


    One thing I'm wondering in all this is, considering the relatively small amounts of water involved in modern energy efficient appliances, whether there would be sufficient time for the water being supplied to be of a sufficient temperature to make it worthwhile. I'm thinking of the length of the pipe run from the tank to the feed into the appliance. I know that with our non-solar setup it can take quite some time for the water to get up to any temperature in the kitchen, and by then a awful lot of cold-ish water has gone through the tap.


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    #3
    MickLimk
    Closed Accounts Posts: 188 ✭✭MickLimk


    I guess that answers question 5 for me! I hadn't even thought about the length of time it takes to run the water before it gets hot...


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    #4
    AckwelFoley
    Registered Users Posts: 12,556 ✭✭✭✭AckwelFoley


    Hello.

    With solar energy systems thats used to heat the hot water for your taps, the system is generally heated to suit your needs. Its not alwys often that you have a surplus of water, and this would generally only be in the long summer days when you have a clear sky.

    The system is designed to have 50L of storage in the tank with a minium of a 250l tank, there fore commonly systems are a 250 or 300L tank. If you were to take a hot water feed for an appliance, you will be cutting into the 50L miin requirement , therefore you would require a much larger tank, if you fail to do this you will lose the benefit of the solar system.

    Both washing machines and dish washers heat their own water, if you were to link these to the hotwater in the tank, and hypothetically, if there was a machine that didnt heat their own water, you would use a rather large amount of water, and instead require a buffer tank, whick in my opinion yould need to be in the region of 600L to cope with that amount of water useage and still not effect your tap water, and then you would also cut into the resivour temp, that you would need as a back up for days of low sunshine and poor heat generation.


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    #5
    AckwelFoley
    Registered Users Posts: 12,556 ✭✭✭✭AckwelFoley


    Alun wrote: »
    One thing I'm wondering in all this is, considering the relatively small amounts of water involved in modern energy efficient appliances, whether there would be sufficient time for the water being supplied to be of a sufficient temperature to make it worthwhile. I'm thinking of the length of the pipe run from the tank to the feed into the appliance. I know that with our non-solar setup it can take quite some time for the water to get up to any temperature in the kitchen, and by then a awful lot of cold-ish water has gone through the tap.

    The length of pipe should not effect the temp of the water if insulated propely with Armoflex insulation, You can have a 100m Loop from solar apnels to tank only loseing aprok 2 degrees, when Armoflex is used.


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    #6
    Alun
    Registered Users Posts: 21,470 ✭✭✭✭Alun


    snyper wrote: »
    The length of pipe should not effect the temp of the water if insulated propely with Armoflex insulation, You can have a 100m Loop from solar apnels to tank only loseing aprok 2 degrees, when Armoflex is used.
    I'm talking about the pipe run from the tank to the appliance, which you may or may not actually be able to get at to insulate depending on where the current pipe runs.


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    #7
    garyh3
    Registered Users Posts: 700 ✭✭✭garyh3


    I have solar tubes with a 300l water tank. Since November (installed) I have had 130kwh put into the water tank. December was the best month so far.

    I think its saving me some money

    Garyh3


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    #8
    Gaothfar
    Closed Accounts Posts: 31 ✭Gaothfar


    Hi Mick,
    Did you install your machines on the hot only, and did it work?


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