This topic contains 16 replies, has 7 voices, and was last updated by  Nick Miles 2 weeks, 1 day ago.

  • Nick Miles
    Keymaster

    Sam you would think so intuitively as air rises, but then again the ground may sometimes be warmer than the air surrounding it. I would think it is immaterial to make a difference. Refer to the manufacturer’s spec for ideal positioning.

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    Nick Miles
    Keymaster

    Have you tried getting through to Daikin with your question? They are usually quite good with a response. I would send them a tweet if you are on twitter even better. Twitter: @Daikinuk

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    Daikin mono block

    Hi can I put a Daikin mono bloc straight on to the return and flow ? We only want to heat the radatiors at 40

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    Sam

    If I put an air source heat pump up higher on the wall (e.g. a couple of meters off the floor) will that increase the coefficient of performance because the air is a bit warmer higher up?

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    Paul Kenyon

    Although you can be sneaky with the order of what you do. Install insulation too early and your RHI payments will be smaller as they are calculated using the heat demand for the property…

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    James Franklin

    Ok, so the bigger the better when it comes to insulation.

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    Henry Campbell
    Keymaster

    We’d recommend filling those cavities. The problem is that heat pumps require electricity to reach the required temperature, and the harder it is to reach (quicker the heat is lost through the walls) the more electricity it uses, which reduces efficiency. Importantly they don’t have the advantage of heating the water to 80 degrees that gas boilers can do.

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    James Franklin

    I’ve heard that. What classes as enough insulation though? I have cavity walls but not filled…is that enough?

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    Henry Campbell
    Keymaster

    Air source heat pumps are a fantastic heating method especially for the off-grid gas properties. Make sure your home is well insulated though. Anyone know someone who has installed one in a poorly insulated property? We’ve seen the electricity bills on a couple and it’s frightening.

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    Susan Shaw
    Participant

    Hi Diedre, they do look at the SPF too. The formula for caluclating the RHI payments for heat pumps is as follows

    Yearly heat demand (bottom of EPC) * (1 – 1/SPF for heat pump)

    This gives you the renewable element of the heat produced because a heat pump requires electricity to run, you then multiply the number by the RHI and this is paid yearly for 7 years. The payment is tax free.

    The Government have worked it out so the payments cover the install cost just about!

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    Deidre Smith
    Participant

    I think Charlie, it is based on the heat demand from the bottom of your EPC. They basically calculate the renewable part of the energy bill and then pay you based on this. So in a slightly counterintuitive way a house that is really badly insulated will get a higher RHI payment. The RHI page on this site is actually really comprehensive so have a read of that.

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    Charlie Watson

    If i had a big enough garden (and a big enough wallet) i would go for the ground-source, but because i don’t it’s ASHP all the way. Am i right in thinking that you only get the RHI on the required space and water heating for your property? or do you get it for the size of the system? I imagine there is a reasonable price difference between small and large systems, but because a lot of the cost is in the actual install and piping etc that it is most cost effective for a large system.

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    Faizal

    For air source heat pumps, is there a big cost difference say if I go for a smaller system vs. a much bigger system?

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    James Alcock
    Keymaster

    Hi Mark, surely based on your comments above the COP for an ASHP changes hugely throughout the year? I agree for a GSHP it would be far more stable!!

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    Mark Langley

    Just to add to the thread about ASHP`s one important factor has not been mentioned, The cop of an ASHP does not fluctuate a great deal throughout the seasonal external air temperature changes but the input and outputs do change dramatically, always read the specification carefully because the installer may claim an output of for example 16 kw but this output is probably only achievable at an outside temperature of + 7 deg C with the delivered heating water temperature at 35 deg C, the same machine running with air temperature at -7 deg C and a flow temperature of 50 deg C will probably only deliver 9 Kw, and very few radiator based heating systems will run at 35 deg C.
    Another very important question to be asked is what is the power consumption of the inbuilt electric supplementary heater and when is it programmed to switch on? As most ASHP`s are cheap converted air conditioning units their primary function is cooling not heating, some even use electric heaters to defrost.Seek out manufacturers who specialize in Heat Pump technology, you will pay more initially for the product but long term pays dividends .
    Mark Langley
    Greenerheat.

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