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Flue heat recovery unit on a sealed system boiler?

Discussion in 'Plumbing and Central Heating' started by Gregory01, 15 Jul 2014.

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  1. Gregory01

    Gregory01

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    Hi

    I am just in the process of deciding on which boiler to put in my house. we are redoing the whole central heating system from scratch.

    I have been advised to go with a sealed system boiler as opposed to a combi boiler.

    As some of you may be aware there is a new government scheme which launched last month which is the green deal home improvement fund. Basically if I choose 2 of their energy saving measures I can claim £1500 cashback towards the cost of them. I am looking to use the boiler as measure 1 and a flue gas heat recovery unit as option 2.

    My question is can you fit a flue gas heat recovery unit on a sealed system boiler or are these just for combi boilers. I have spoken to 2 different companies regarding this and 1 says its only for combis and the other says it will work on both.

    Any help would be much appreciated.

    Many thanks
    Greg
     
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  3. Plumber90

    Plumber90

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    To be honest I'm not sure if they can as they are fairly new, but they aren't going to save you anywhere near the amount they will cost to install in their lifetime.
     
  4. Gregory01

    Gregory01

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    I understand that from a monetry point of view they might not normally be a wise investment, however with £1500 cashback under the new scheme it seems to make sense to get one. I can get the boiler installed and fitted for less than it would cost in parts for the boiler + cylinder + heat recovery unit.

    Obviously though I dont want one installed if it doesnt work with a system boiler.
     
  5. Dan Robinson

    Dan Robinson

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    With the information you have provided we can't give too detailed a response.

    However... I would say that they would be pretty pointless on anything other than a combi simply by how they work and what they are designed to do.
     
  6. shray

    shray

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    As far as I'm aware, although I may be wrong, the idea of them is to increase the heat of the cold feed water into the boiler by roughly 3 degrees or so and consequently reduce gas consumption on hot water demand only.
     
  7. transam

    transam

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    Flue heat recovery on systems or heat only boilers is not new the principle was used on numerous atmospheric condensing boilers, still is by some ?

    Most of the FHR units offered by manu's are probaly the Zenex design used under licence from them.

    The other one would be the Ravenheat "energy catcher" which is basically the same or slightly modified version of the recouperater they were using on there condensing boilers in 1996

    There are 2 versions of it the "combi plus" & the "combi store" the combi store concept I believe ?? is unique to them i.e no one else is doing such a set up ?????

    I am not aware of any manu who offer a set up for boilers other than combis .

    Although there are various configerations offered or suggested by Ravenheat for the energy catcher i.e connected to a remote HW cylinder ?
     
  8. Dan Robinson

    Dan Robinson

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    Would have thought the restriction to flow would be too much on a decent system.

    Mind you - judging by the OP's approach to this, a decent system is the last thing he is willing to pay for ;).
     
  9. Gregory01

    Gregory01

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    Thanks for the replies on this. I will give valiant a call in the morn and ask them as it doesn't seem to be common knowledge.

    Dan Robinson - what do you mean by the restriction to flow would be too much on a standard system?

    Also keen to understand your last comment. Is there a better system I could go for. Obviously the cheaper option is to go with a combi, keep existing plumbing etc. I think you have this the wrong way round, I'm looking to get a descent system and am happy to pay for it whichever one that is. A sealed system boiler was recommended as being better than a combi (make of that what you will) but I'm happy to pay for it if it's the better option. What's your point?
     
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  11. newbuildinstaller

    newbuildinstaller

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    We fit Logic Code combis in this scheme the Flue unit is built into the boiler
     
  12. Gregory01

    Gregory01

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    Thanks for the reply new gas installer. The logic has been suggested to me already as they have everything built into the boiler. It's a good idea and I'm assuming may have been designed to take advantage of the new scheme.? Anyway, looks like a good option except it's a combi.

    Thanks for the suggestion.
    Greg
     
  13. Agile

    Agile

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    The heat recovery device is intended to be used to heat water on the inlet to a combi. although another heats water in a small cylinder.

    There is no reason why it can not be used to preheat water to feed a normal cylinder.

    But issues can arise if the preheated water is stored for long at a legionella breeding temperature of about 25 C to 35 C

    Tony
     
  14. shray

    shray

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    I'm not sure I understand how that could possibly work. On a normal vented cylinder the water would have to go through the heat revovery unit after leaving the header tank but before it reaches the bottom of the cylinder right ? Is that your thinking on it ? if that is your thinking then the boiler position would have to be below the level of the header but above the cylinder. And then the recovery unit would only be of benefit when the boiler is on, which in the case of a heat only/system during the summer would be very little.

    Sorry if this isn't what you meant.
     
  15. Terry lambert

    Terry lambert

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    If it's purely to get the £1500 cash back.

    Then why not fit the combi with the heat recovery, run the hot outlet to the kitchen sink and then use the boiler as you would a system boiler on S or Y plan.
     
  16. Gregory01

    Gregory01

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    Thanks to everyone for their help on this. For anyone in a similar situation the answer is no, the valiant system boilers will not benefit from a flue gas heat recovery unit, these are only designed for combis.

    The solution which has been advised is to go with a valiant 631 combi with heat recovery unit installed. That is then eligible for the cash back. In addition to this they are going to fit a 250l pressurised cylinder which will be heated by the boiler and / or solar panels which we plan to fit when funds allow. The heating will be run directly through the boiler and we will have the cylinder which will mean is 2 showers are run at the same time there will be enough hot water at mains pressure.

    From what I understand this seems to be a good setup. All the benefits of a combi but without the downsides (issues when running 2 showers at the same time). It also has all the benefits of a system boiler but with the advantage that if we use all the cylinders water we still have hot water through the combi. We also have an immersion heater in the cylinder so if the boiler breaks down then we still have hot water.

    This seems like a great solution and I'm struggling to see why this is not more common. Am I missing something? Any feedback from people "in the know" would be great.

    Thanks again
    Greg
     
  17. Dan Robinson

    Dan Robinson

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    Atag A325EC has the FHR built into it and will cost less than the Vaillant.

    A better boiler too IMHO.

    Flue gases around 20 degrees Celsius when running full pelt for hot water :eek:
     
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