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  1. #1

    Default Octupus Ice-Stick Heat Pump

    Hi,

    Has anyone here ever heard of this 'Ice-Stick' type of heat pump manufactured in Sweden, good or bad?

    Irish Distributer
    http://www.hotfoot.ie/porcelanosa/Ho...ure%202008.pdf

    Swedish Manufactuer
    http://www.octopus.tm/eng/index.htm

    Dgray_ie

  2. #2

    Default Ice Stick Video

    See there are a few Ice Sticks installed in Ireland see link to references below:

    http://www.hotfoot-heating.com/references.htm

    also link to video of installations below:

    http://www.youtube.com/watch?v=EUVp6...eature=related

    What do the heating experts out there think, are the figures mentioned in the references possible?

    Dgray

  3. #3
    Join Date
    Oct 2009
    Posts
    8

    Default Ice Stick

    Hi DGray,
    I'm not a huge fan as they don't do hot water - you still need another hot water heater and immersions run at COP of 1. you can get air to water heat pumps and ground source heat pumps that supply a COP of 3.8 - 4.5 to heat and provide hot water.
    Solar only provides hot water on average 25 - 27% of the time.
    I've already sent you a private mail with suggestions for your own heating.
    Feel free to ask any questions by e mail.

  4. #4
    Join Date
    Mar 2006
    Posts
    1,256

    Default buffled....

    Hi DBEP!
    You wrote:
    "..... you can get air to water heat pumps and ground source heat pumps that supply a COP of 3.8 - 4.5 to heat and provide hot water...... "

    I have never seen or heard about a heatpump which can deliver to the tap domestic hot water with a COP of 3.8-4.5.....would you have any references?

    Thanks.

  5. #5
    Join Date
    Mar 2006
    Posts
    1,256

    Default re.

    Actually heatpumps do not deliver domestic hot water at all......
    What they do is that they provide a closed loop heating circuit which in turn provides a storage/buffer tank with thermal energy.
    Similar to the ordinary copper cisterne suplied via the central heating.
    Each heat exchanger causes a temperature drop of several dgrees, a well designed and installede AND well maintained heatexchanger will 'loose' 5 degrees Celsius....

    Meaning if the DHW in a pressurised storage tank has to be heated up to 60 degrees Celsius then the heatexchanger in it has to be 65 degrees Celsius hot at it's external surface. After running through the whole house, from the HP to the storage tank what involves thermal losses of course as well...
    Not covering the ongoing thermal losses from the storage tank which would have to made up for as well....
    Ask your HP 'expert' for the COP of such an installation.

    Therefore the stated COP of the HP manufacturer is irrelevant. Not to be relied on when looking at the DHW output. Or at the energetic effiociency of a space heating system.Smoke granades to fool the incompetent consumer who doesn't understand the system.
    Storage and transport losses as well as the electric energy demand of the transport (the circulation pump) has to be subtracted from stated COPs.
    And these losses forbid to choose for a HP as an economical or ecological thermal energy source to suply DHW.

    But sure DBEP knows that as well......

    @Dgray_ie:

    Ask for the anual electric energy demand to be guaranteed in writing (kWh/ year). And you'll see how they buck out.
    Last edited by heinbloed; 5th January 2010 at 03:45 PM.

  6. #6

    Default Efficiency of Heat Pumps

    Heinbloed is absolutely correct in highlighting that the Stated COP of a heat pump is unlikely to be representative of the actual efficiencies of the system over all when trying to deliver hot water temps of 65 degrees.

    In fact the stated COP is usual measure at a range of temps from -5 0 +5 +10 degrees collector temp and 35 and 50 degrees flow temp for the Plate. Most manufactures will find the most efficient rating usually 5 and 35 and advertise this usually between 3.5 and 4:1 COP.

    However I would argue that it needs to be viewed a different way,
    A Heat Pump and by that I mean the compressor, evaporator, throttle and plates. Is an inherently efficient set up, and the COP of this is a moving target, depending on the temperature of air or liquid hitting the cold side and the temp of the fluid hitting the hot side.

    In fact as this system moves from stand still to its desired temp, it will start with COPís as high as 7 or 8:1 and fall steadily to as low as 1.5:1.
    This therefore is a devise that will range from 150% efficiency to 500% plus assuming that your source of heat for the cold side is free and renewable. The goal obviously is to keep it at the high efficiency end as much as is possible.

    If you are trying to get hot water to 60 degrees and it starts at 25 then a good period of this time will be spent at high efficiencies, if it starts at 50 then it is different. The trick therefore, as with the heating circuit is to give the system a load to work on and spend as much time as possible at low temps. If this is done it is reasonable to expect the Heat Pump to average a High COP of 3.5 plus.

    The circulating pumps will not affect the COP greatly; the cop of the electricity distribution is more of a problem as is distribution heat loss and bad design.
    (I spent a decade installing Condensing Boilers in the UK, and under Part L many years ago there any new boiler had to be replaced with a condensing one. As it was argued that it was 90% efficient and the old ones 65-70%. A study was carried out many years after this scheme was started to assess the running efficiency of the boilers, and it was found that only about 20% of them where actually condensing as the Delta t was to small and to high on the Flow and Return pipes from the boiler and the majority of them where running at similar efficiencies to the replaced ones)

    So beware of people claiming extravagant things of Heat Pumps but also beware of people claiming they are all bad. A Heat Pump is an inherintly efficient thing, it is the cost of it, the temp you run it at and the the efficiency of the electricity that supplies it that need to be weighed up.

    As with Solar Panals, Biomass, PV, Wind and anything else you care to mention, you have to do the maths yourself, ensure as best you can correct deseign and installation and and take a long view on cost of suppliying it with the fuel it needs.

    Regards

    Simon

  7. #7
    Join Date
    Mar 2006
    Posts
    1,256

    Default re. delta Tof condensing boilers

    Sjones Aereco wrote:

    " (I spent a decade installing Condensing Boilers in the UK, and under Part L many years ago there any new boiler had to be replaced with a condensing one. As it was argued that it was 90% efficient and the old ones 65-70%. A study was carried out many years after this scheme was started to assess the running efficiency of the boilers, and it was found that only about 20% of them where actually condensing as the Delta t was to small and to high on the Flow and Return pipes from the boiler and the majority of them where running at similar efficiencies to the replaced ones)

    So beware of people claiming extravagant things...."

    Sorry, sjones aereco, but you have not understood after 20 years of installing condensing boilers why a condensing boiler is more efficient then a 'non-condensing' boiler?!

    The temperature difference between the flow and return temperature (you describe it here as delta T) is absolutly irrelevant.

    The fluegases condense because they hit a cold surface, the heatexchanger.

    Not the condensing of the flue gases makes a boiler efficient but the energy content (temperature) of the fluegases. If the released flue gases' temperature is higher then the temperature of the incoming air then energy is wasted.
    The larger this difference is the more energy is wasted.
    This effect on the energy efficiency has nothing to do with the Delta-T of the flow and return pipe.

    Compare it with a building: no Delta-T (well, zero) between inside and outside and you can leave the windows open. Since no energy will be lost from the building.
    No matter if the temperature in the building is +20 degrees Celsius or +5 degrees Celsius.
    The Delta-T of the flow and return pipes of the central heating system simply doesn't matter.
    As long as the Delta-T between the incoming air is the same as the outgoing air there is no energy loss. Irrelevant of the Delta-T between the flow and return pipes of the heating system.
    The same goes for the combusting boilers.
    Their efficiency is meassured by subtracting the energy content of the incoming air which is needed for the combustion process from the energy content of the outgoing air, the flue gases.

    This is according to SEDBUK.

    Again: the Delta-T of the flow and return pipes has nothing to do with this calculation, the efficiency of the boiler. It will influence the effiency but it is not the factor to calculate the efficiency of a combustion process, for example for a condensing boiler.

    Or in more simple words:
    Condensing boilers do not have to condense to be more efficient then other 'non-condensing' boilers. All they have to do to be more efficient is to reduce the energy content of the outgoing air, the flue gases, when compared to some other combusting boiler.

    Which is done via the bigger and therefore more efficient heat exchanger.
    Since the heat exchangers of condensing boilers are larger then the heat exchangers of 'non-condensing' boilers the condensing boilers will be always more efficient then the non-condensing boilers.
    Do you have any references to the mentioned study?
    Last edited by heinbloed; 6th January 2010 at 10:03 AM.

  8. #8
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    Mar 2006
    Posts
    1,256

    Default Efficiency of heat pumps

    The COP of heatpumps do not show how efficient a heating system supplied with a HP is.

    Always get the efficiency of the heating system guaranteed. Ask for the consumption of kWh per year. And get this into the contract, written and signed.

    Demand your money back if the predictions fail.
    A contract is legally binding to all parties who have signed it.
    Make sure the person who signes it has the financial capeability to come up not only with the money-back guarantee but to supply you with a functioning heating system if the first one fails.
    Functioning under the guaranteed conditions.
    Get the anual kWh consumption of the heating system guaranteed. NOT the monetarian fuel costs.
    A heating system which has to be ripped out because it doesn't do what it says in the contract and needs replacing with a bog standard boiler will reduce the value of the house. Esp. when there is no space for the oil tank, timber pellet storage, no gas connection.
    You might get another boiler, but make sure you get the fuel as well. And that your building's energy rating doesn't go down when being forced to switch.
    And that the local building regulations allow for a switch. Not every neighbour is happy with an oil boiler roaring and stinking next to his windows, next to his ventilation system.

  9. #9

    Default Boilers

    My apologies, not very well explained and only meant as a metaphor!

    This was a thread about Heat Pumps so do not want to get dragged into long discussion so please see bellow short explanation.

    Of course the Delta T does not create the efficiency but as you pointed out it will influence it.

    What was happening was boilers where being set at two higher temp and where over sized. (This was because, traditionally, and still often the same, there is not great increase in price from a 24kw to say 36kw boiler) And the plumber would just oversize to be sure he would not get a call that the house was cold)

    So the boiler would very quickly get up to and stay at and cycle at a very high temp meaning the Flow and Return Temps where close together and High.

    The boiler stopped condensing and most of the heat just pissed out the flue. Even though the boiler was able to modulate.
    The point of the larger heat exchanger is to absorb as much of the energy as possible. If the temp of that heat exchanger is very high then its ability to absorb energy from the combustion process is reduced, condensing is just a by product of the process when flue gases are below a certain temp I understand this.

    My point to make was that an inherently efficient device can be made inefficient by bad design and installation. It was a thow away comment and my apologies if it added any confusion.

    I will see if I can dig the report out for you, it was well over ten years ago, and I am not sure who did it. Possibly for CORGI? or the energy efficiency label ?

    Anecdotally though this was my experience in this period.

    Hope that clears it up. And thank you for such close scrutany of that particular paragrph, I will be sure to repay the compliment at some point!

    Kind regards

    Simon

  10. #10

    Default Octopus Ice Stick

    I have decided to post on this forum to clear up a few things about the Ice Stick.
    We have installed about 40 units over the last few years and many of these machines have Kw/hr meters. These meters measure heat pump, auxillary and circulation pumps. The quoted figures in our testimonials are fact. These can be verified by our very happy customers who are more that happy for anyone to see their installations.
    In my experience, difficulties with heat pumps arise mainly for the following reasons:
    1. The heat pump installed is too small for the required load.
    2. The dwelling isn't sufficiently insulated and has excessive draughts etc.
    3. The homeowner does not understand the principles of a heat pump and therefore expect the systems to work like a conventional high temperature heating system

    Octopus does not believe in using the compressor to generate hot water for DHW use but to instead preheat the cold water feed to the tank with a heat exchanger on the return of the heating system. This will save aroud 50% on normal emersion demand. This increases the working life of the compressor.
    The compressor is the only moving part on the Ice Stick.
    This is why we can say that no maintenance is required for the Ice Stick.
    We now have a DHW heat pump that only uses a 800W compressor for DHW demand. These units cost about Ä80 pa for a standard dwelling.

    Please feel free to contact me at jleonard@hotfoot.ie if you have any questions.

    Regards
    Jonathan Leonard
    MD Hotfoot Ltd.

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