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Thread: Koi house

  1. #41
    Some thoughts on heating your pond......

    The total running costs of various heaters are not always that simple to work out.

    For most of us, electricity is approximately 4X the cost of mains gas per kWh.

    In an electric inline heater, 100% of every kW makes heat, so let's say that costs 15p per kWh.
    As a standalone system, this is the easiest to install (other than drop in heaters).

    A gas boiler and heat exchanger system may be 85% efficient (boiler itself is higher than that), so in comparison that would cost 4.3p per kWh.
    This can be a cheap install if you can make use of your existing gas boiler system, but expensive if you need a dedicated boiler and gas supply.

    How about an airsource heat pump?
    I will assume you heat the water to between 15-20 degrees (heat pump COP is very much affected by water temp required).
    The efficiency of the heatpump will vary a lot depending on air tempreature and if it's cold, air humidity.
    If the air is at 0C, a decent heat pump will have a COP of about 4 to heat to 15/20C. This suggests a cost of 3.75p per kWh.
    A good (and there are some not so good ones so beware) ASHP will cost a similar amount to a new gas install for a low heat output unit suitable for a pond application.

    ASHP notes:
    If the air is cold and humid the condenser on an ASHP can freeze and the unit will need to defrost. This will increase running costs significantly during the defrost cycle.
    As air temperatures rise the COP will rise and the cost per kWh can come down to about 3p per kWh. Of course as the weather warms up less heat is required and the very highest COP values of an ASHP aren't really relevant.

    The above is based on my own experience, but there will be proper experts out there who will be able to give more accurate info.
    I hope it has been of some use.
    My DIY ponds from 1988 until present day.
    All can be found here:
    https://www.ukzero.com/pond.htm

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  3. #42
    Senior Member Rank = Nanasai GadgetBazza's Avatar
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    Completely agree on what UkZero has added.

    To re-iterate, don't pay too much attention to the max CoP figures quoted, they are largely irrelevant as they require ambient temps of 28c and water temps of 25c to achieve it!

    One variant in your requirement that I've never had to consider though is because you are indoors, your best bet as far as I can tell is to heat the room and not the pond, the pond will absorb this heat and gradually the pond temperature will match the room temperature, then you just need to maintain the room temperature. This will be a relatively low and slow approach, which is actually perfect for inverter heat pump technology as it is more efficient when operated at lower differential temperatures.

    Hopefully as UkZero said, there is an expert that can add to this, particularly with the view of heating the room rather than the water.

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  5. #43
    And I agree with GadgetBazza. If you have an indoor pond then heating the air makes much more sense than heating the water.
    Why?
    High volume air to air transfer is what heat pumps do well.
    Because the room warmth is now heating your pond, the water temperature will be lower than your planned/current room temperature which is vital to reduce condensation.
    I can guarantee that if you have a warm pond in a cold room you will get a cold wet room.
    My DIY ponds from 1988 until present day.
    All can be found here:
    https://www.ukzero.com/pond.htm

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  7. #44
    Member Rank = Nisai Robo76's Avatar
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    Thanks ukzero I will bare that in mind and try to way up the costs along with the pros and cons

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  9. #45
    Member Rank = Nisai Robo76's Avatar
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    Hi John
    yep and that’s with me digging it all up ready for them

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  11. #46
    Extreme Koi Member Rank = Supreme Champion john1's Avatar
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    I wonder what depth a gas pipe has to be when buried.
    John

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  13. #47
    Senior Member Rank = Supreme Champion Ajm's Avatar
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    Quote Originally Posted by john1 View Post
    I wonder what depth a gas pipe has to be when buried.
    Electricity is 500mm so would have though bit deeper ??
    Freddyboy the legend

    "we are water keepers first"

    Johnathan

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  15. #48
    Member Rank = Nisai Robo76's Avatar
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    Hi
    yer about 500-600 but I have seen them just under tarmac before and over meter deep all depends on the people doing it lol

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