Air Source Direct Hot Water Cylinder - Design Concept

Discussion in 'Eco Talk' started by MarkD77, Aug 29, 2019.

  1. MarkD77

    MarkD77 New Member

    Hi All,

    Thank you for letting me join the forums, here at Screwfix.

    I am a qualified electrician and I am very much into green technology and audio visual, I am in the process of purchasing a new property and I have bought a Dimplex Air Source Heat Pump Cylinder (uses air and AC gas to generate heat).

    I have a concept design, but I don't know enough about ventilation to know if the idea will work.

    My idea is:
    • Use the warmer air from my AV rack to help with the air heat that the cylinder by pulling through the AV cupoard warmth.
    • It's a little bit more complicated because I am installing an MVHR ducted system that will also re-use the av cupboard heat to help warm the house in the colder months.
    • The Cylinder will not be running often as it will need to top up the hot water or quite often after a bath etc.
    • I planed to use a solenoid on the 75mm MVHR ducting to close the MVHR pipe once the fan runs on the air source pump.

    I have attached a picture of the design which will probably explain it more than this post, I wanted to get some feedback on the potential problems that this could cause and maybe if its even worth doing.

    Thank you very much for any help you can give or critic :)

    Screenshot 2019-08-29 18.14.18.png
  2. kiaora

    kiaora Well-Known Member

    I don’t really know a lot about heat pumps, I know how they work, but, I do understand the unit is designed to use ambient air temperature and release the heat in it.

    We have to remember, if the out side temperature is minus 10 c, it’s actually plus 260 degrees Kelvin !
    It’s full of heat ,!
    Altering the installation instructions to draw air from other sauces my invalidate the guarantee.
    And introduce moisture into the unit.

    On balance, considering the extra cost on materials, with very little saving, and added risk of invalidating the guarantee, I’d vote fit as per manufacturer instructions.

    Good luck, peter

    Ps, you can get taps and shower heads that use less water, ? Saving hot and cold water!
  3. ajohn

    ajohn Well-Known Member

    I would wonder about the running costs of this type of heater and the output. It would be interesting to have some hard facts from some one that actually uses one. In real terms they are a variation on a fridge/freezer which is why the radiators on the back of those get warm. When ever heat is extracted it has to go some where so usually these heaters are cooling outside air and transferring heat into a building. In principle the temperature of the air it's cooling doesn't matter so in this case it would be cooling the AVR cupboard when it might be better to just let that escape or use it to preheat. Energy will be being used to cool the cupboard. What's happening in a simplistic sense is 10C in one place is being transferred to 20C somewhere else. In real terms though watt are being transferred and used to do that.

    I could have a spout about the current methods that are available for heating partly because of hearing about boilers being replaced with electric ones that use a pumped system. These can not be as efficient as panel heaters as electricity can be transferred to heat at virtually 100% efficiency but then comes the panel heaters that are available and heat up times. The latter could mean that heating needs to be on 24hrs a day. All work though seems to be on gas heating which can not be very efficient - unless maybe hot air but even that will have losses.

  4. CraigMcK

    CraigMcK Well-Known Member

    Heat pump solutions are significantly more efficient than electric panel heaters. They are in the region of 300%, depending upon weather etc. That is for every 1 Joule of energy in you get 3 out by way of heat.
    I have a small 12000 BTU (900W input) unit in my office and even in the winter it keeps it hot. I would never get that from a 900w panel heater. What is even better, in the summer it cools too if the open door does not do enough.

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