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Renewable Energy: Installing new oil fired system - make provision now for solar?

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    I am installing a new oil fired boiler and plan to install a new unvented cylinder.

    Its worth noting at this point that my future plans include installing a wood pellet boiler, however, with my old boiler on its last legs and winter approaching, I've not got the time to fully evaluate the wood pellet option, so have had to bite the bullet and buy a new oil boiler (Grant Vortex Pro). Going forward I plan to retain this alongside the wood pellet boiler.

    Now my question - Should I install now a twin coil cylinder for future solar collector, or just get a single coil and make provisions for solar within the future wood pellet install (which will include a substantial thermal store)?
    • CommentAuthortony
    • CommentTimeSep 18th 2011
     
    Twin
  3.  
    Unless you plan a big SWH system (10 - 25m2) to play a part in space htg. If a normal 4m2-ish system, agree with Tony - twin coil.
  4.  
    thanks - since I asked the original question I'm now pondering should I go for

    unvented twin coil cylinder VS thermal store ?

    seems there's a lot for me to learn since I installed by last heating system (20 yrs ago!)
    • CommentAuthorcrusoe
    • CommentTimeSep 19th 2011
     
    Me for a 300-400 litre TS, cos you can put more than 2 inputs into it. And is better with lo-temp apps like heatpump than coil. Can even feed it from large TS. World's your oyster....
    • CommentAuthortony
    • CommentTimeSep 20th 2011
     
    vented for me
  7.  
    OK - speaking to a "heating engineer" who has priced me the Wood Pellet system, he wouldn't recommend a thermal store for an oil boiler/solar combination. As my store would be located on the ground floor, the heating cct (radiators) would need a coil, hence he says the boiler needs to heat the store up to a higher temperature to heat the radiator cct (via a coil) and will be less efficient than an unvented cylinder

    Further comments?
  8.  
    Hi,

    try to be clear on a thermal store purely for the DHW or a thermal store for the future pellet could be either. As you mentioned a UV cylinder this could be a direct or indirect store with a coil for DHW.
    Likewise you could have a direct but vented store downstairs for the pellet boiler - this would need an exchanger for the rads which in coil form might be inefficient - plate X is fine for this.
    Many combinations - the garnt could feed a DHW store just like any other boiler via a coil or be direct.

    And - any reason why the wood pellet themal store cant be direct and presurised on the primary side?

    Cheers
    mike up north
  9.  
    Sorry Mike (Up North) but I'm now more confused than ever.

    The questions I'm trying to answer are:

    1) Should I bother fitting a cylinder with a solar coil now - answer seems to be yes

    2) Should I stick with an unvented cylinder or choose a vented thermal store - answer no idea

    3) For the thermal store option does it just do DHW or do I run the rads off it too - answer no idea

    4) I'm fitting a multifuel room stove (only @ 5kw) do I bother going to the trouble of buying the stove with a 2kw output backboiler element and run this into the thermal store - answer no idea (doesn't seem worth it for 2kW)

    5) how do I size the thermal store - answer no idea

    So basically I've got no idea, and I'm just looking for some impartial advice to make an informed decision

    Help:sad:
    • CommentAuthorowlman
    • CommentTimeSep 29th 2011 edited
     
    For the future if you go down the thermal store/accumulator route you will need to size this according to the Kw output of the future pellet boiler. Once installed you can input heat into this large water tank from any damn source you like. In your case you can have it "direct" off the pellet boiler and also re-connect your present oil boiler as a back up. The water in all three bits, the pellet boiler, the tank, the oil boiler, can be one and the same ie direct, dirty water, no coils etc.. it's also the same water as in your rads. Now if you want to put sol;ar heat into this large tank (possibly 2 to 2500l ) you are probably going to need one hell of an array to get any benefit, so maybe out of the question.
    Having got this vessel of hot water, now to decide how to use it. Rad circuits are the obvious first step, preferably zoned. DHW can be provided via a PHx or an internal coil within the accumulator with no DHW cylinder required. That leaves the question of solar. If an extra large array, as previously mentioned, is out of the question. Then the way to go may be to have a DHW cylinder with two coils, one feeding off this "hot store", in practice just like another rad circuit with its own controls, and the second drawing heat from a more reasonably sized rooftop solar thermal array.
    To try and marry your present needs with any future plans is the problem but not insurmountable. In your case, for the present, I would go for a twin coil unvented solar cylinder. Connect one coil to your oil boiler along with the usual rad circuits. Connect the other coil to a ST array, all fairly standard stuff. Then when you decide to upgrade and install the accumulator, dis-connect the oil boiler from its coil and re-connect it and the new pellet boiler direct into the tank, and then re- connect the now defunct DHW cylinder coil off the accumulator, obviously with the correct controls.
    Hope all that makes sense, apologies for the lengthy explanations.
    Regards, Mike :bigsmile:
  11.  
    Owlman - thanks

    (thankfully) that confirms the conclusion I had been coming to but you have blown away all the cloudy bits

    Stu
  12.  
    naywansteepanuf,

    agree with Owlmans comments above, but perhaps there ia an even simpler first step - just install an oil boiler that does instantaneous DHW, plus feeds the central heating. All Owlmans comments still stand about re-connections later when you go for the full monty, but you won't have had to buy/install a cylinder etc, that might not be of any use later. Leaves all options open for later.

    Just a thought. GreenPaddy.
    • CommentAuthorwookey
    • CommentTimeOct 3rd 2011
     
    I don't understand why your 'heating engineer' says you need a coil for rads if thermal store is downstairs. That's nonsense (unless the thermal store has the header tank built in to the top of it). The store just runs at ~0.2bar higher pressure if moved downstairs. Also I don't really agree with the idea that you have to have a large solar array just because you have a large store. Firstly you (approx) get the same amount of energy out of the panels whatever the store size, and secondly you can optimise the degree to which you get a useful small volume of hot water rather than very large volume of slightly warm water by suitable system design (stratifying solar inputs rather than bottom coils, for example).

    If you do end up buying a tank before tall he rest of the system, then a thermal store with a range of inputs will give you a lot more fleibility than anUV cylinder, but as has been pointed out, the store is actually the centre of the system and it's hard to choose correctly if other aspect remain uncertain.

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