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Heating and cooling: accumaltor tanks

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  1.  
    Forgive my ignorance but do accumulator tanks (AkVAir etc) need a power connection or do they work like ‘traditional’ hot water cylinders?
    I'm just wondering if you would still be able get DHW when the power goes off via a stove/backboiler and accumulator combination. I live pretty rural so it is quite a frequent occurrence for the power to go off.
    Ben
  2.  
    It depends on the details of the tank.

    If the incoming water supply goes through a coil inside the thermal store to get warmed up then it would still work in the event of a power cut. (Tank in tank is effectively the same.)

    If the incoming water supply was heated through an external (plate) heat exchanger then this normally requires a pump and would not provide hot water when there was a power cut. You would just get cold water from the hot water tap.

    There was a thread recently discussing the merits and drawbacks of each scheme: http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4875

    Although operation in the event of a power cut wasn't one of the points discussed, but it should have been.
  3.  
    Go on then MarkBennett - what happens in the event of a powercut?
  4.  
    Posted By: mrswhitecatGo on then MarkBennett - what happens in the event of a powercut?


    Posted By: MarkBennettYou would just get cold water from the hot water tap.
    •  
      CommentAuthordjh
    • CommentTimeDec 8th 2009
     
    "what happens in the event of a powercut?"

    Apart from Mark's answer, the other answer is that low power low voltage adjustable speed pumps are available and well-suited to saving energy in driving a PHE circuit. So add a battery back-up unit if you want hot water when the power's off. Yes, it's more complication :(

    Cheers, Dave
  6.  
    Posted By: djh"what happens in the event of a powercut?"

    Apart from Mark's answer, the other answer is that low power low voltage adjustable speed pumps are available and well-suited to saving energy in driving a PHE circuit. So add a battery back-up unit if you want hot water when the power's off. Yes, it's more complication :(

    Cheers, Dave


    Yes, I was considering some form of UPS or battery backup to maintain critical pumps during a power outage. However, we have so few power cuts that I don't think it is worthwhile. Might try to design the system make the provision for it in the future though.
    • CommentAuthorCWatters
    • CommentTimeDec 8th 2009 edited
     
    Looking at this diagram..
    http://www.akvaterm.fi/images/kaaviokuva_460.jpg
    from
    http://www.akvaterm.fi/eng/accumulators/Akvair_solar.41.html

    Looks like if the tank is hot you should have hot water in a power cut. It appears mains pressure will push water through the heat exchanger coils.
  8.  
    My concern is more the safety aspect of it (I don't see me wanting a hot shower in the dark - I can wait until the lights come back on) - how important is it that the Akvair pump shown gets electricity?
  9.  
    Posted By: CWattersLooking at this diagram..
    http://www.akvaterm.fi/images/kaaviokuva_460.jpg" >http://www.akvaterm.fi/images/kaaviokuva_460.jpg
    from
    http://www.akvaterm.fi/eng/accumulators/Akvair_solar.41.html" >http://www.akvaterm.fi/eng/accumulators/Akvair_solar.41.html

    Looks like if the tank is hot you should have hot water in a power cut. It appears mains pressure will push water through the heat exchanger coils.


    Yes, the standard Akvaterm stores use a coil inside the tank to provide hot water rather than a plate heat exchanger, so you are correct. There are pros and cons to internal coil/tank vs PHE, but this isn't the thread to discuss them (see my earlier post).
  10.  
    Posted By: mrswhitecatMy concern is more the safety aspect of it (I don't see me wanting a hot shower in the dark - I can wait until the lights come back on) - how important is it that the Akvair pump shown gets electricity?


    Whether using an internal coil or a plate heat exchanger system I can't see there being any safety issue. In a coil system everythign works as normal but in a PHE system you just get cold water out of the hot taps. There's nothing to overheat or go bang as far as I can see.

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