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Author Topic: Thermal Store on my mind  (Read 13552 times)
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« on: October 12, 2008, 08:36:59 AM »

Hi learned readers - would very much appreciate ur advice: I've got big old Victorian terraced house (high ceilings) want to go wood, and then solar maybe also in year or two. I also have a relatively new combi boiler (that is not big enuf to do whole house...was originally 2 flats, upstairs and downstairs, now being converted into one big house).

I've thought about log boiler, but my sheds are 20m or so from house - too far I gather, technical issues? - not sure I want to build another structure closer to house, as well as cost of installation of log boiler.

So am thinking about wood burning stove, with gas boiler as back up. Should I get a Thermal Store??? - I understand they are helpful to connect multiple systems (stove with boiler, gas boiler, solar). I also like idea of thermal store providing heat (water, rads) in the winter mornings, otherwise where has all the heat gone from the night b4?? (waste).

Question - what size thermal store wood (ha!) I need - 750 litre? - can I get something this size into house or would it need to remain outside??

Question - would the heat I get in mornings from such a store (750??) be worth my while? - I mean spent installing, amount of wood burned etc. Would I be better not  thinking in terms of storing heat?? - I read abit about the H2 control product, maybe I should just keep it simple with one of these (can they connect solar too?)

Could people recommend specifics in terms of size and products for thermal store?

Huge thanks, I need help.
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« Reply #1 on: October 12, 2008, 09:08:35 PM »


I know he's around here somewhere....

changing the world, one roof at a time.

Quality is never an accident; It is always the result of
high intention, sincere effort, intelligent direction, and
skilful execution; It represents the wise choice of many
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« Reply #2 on: October 13, 2008, 01:30:46 PM »

I'm a 'newbie' myself, so probably others more qualified to respond. I do have a Log boiler (Atmos 40kW - and a thermal store (2000l Akvaterm), so my experiences so far may help you.

Firstly the sheds. Not sure why 20m would be too far. Heat loss will need to be taken account of, lots of insulation on the pipework goes without saying. Increased pump size possibly, but nothing too challenging.

One issue may be the flue height. These boilers need a decent height of flue, I think for my own the recommended height is 10 - 12 metres. If the shed is single storey, this would leave a large self-supporting flue to construct. The boiler itself is not massive, you could probably find space inside somewhere. The main issue is having easy access with the wheel barrow from the log store.

However, the thermal store is another matter. 750l sounds quite small. My store is 2000l, which is smaller than the manufacturer's recomended 2500l, but it is all I could fit in! I have planned ahead with my store, and have made provision for future solar and hydro-electric input. When you're shelling out that amount of cash it seems daft not to plan ahead.

In summer, with just the hot water demand, I fire my boiler a little less than twice per week, and I have to confess to owning a large wasteful bath, when I get solar, I would think that summer boiler firing would be a rarity. I am still building my home (watermill conversion), and this is the first winter with heating connected, but at the moment the underfloor heating when on will sap the heat quite quickly, and the boiler needs firing daily. Although I have yet to insulate the building.

I'm not sure what the 'h2 control' is, (I did try googling it), but I would say that with a batch-fed log boiler, a thermal store sized as close to the manufacturer's recommention as possible is required.

I am happy enough with my Akvaterm thermal store, plenty of links on Google, the most cost effective solution is a single, large cylindrical tank, although if access into existing buildings is an issue, multiple smaller tanks can be connected, or an oval tank to fit through doorways is also available.

Good luck, and with a log boiler, you don't need Gym membership!
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« Reply #3 on: October 23, 2008, 09:12:19 AM »

Morning Undecided,

A fully charged, well stratified 750 litre thermal store will hold just shy of 40 kWh worth of usable heat (less losses), based on a working temperature range of around 45 to 90 degC, but obviously this will be reduced if you are using high temp rads instead of low temp UFH etc.

Another thing to consider is the weight of the store: 1000 litres = 1 tonne plus the self weight of the store, so make sure the floor can handle this load.

If it's a large house with a high heat demand, then you would be wise to reconsider using a dedicated high efficiency log batch or woodchip/pellet boiler, rather than a WBS to heat the DHW and run the CH.  And if you wish, you could also have a stand-alone (without back boiler) WBS as a additional heat source in the main living area for those cozy nights in.

Here's a couple of earlier threads that may be of use....,4857.msg47742.html#msg47742,4110.0.html,4654.0.html

Good luck,


« Last Edit: October 23, 2008, 12:05:08 PM by lightfoot » Logged

Mother Nature is a wonderful housekeeper - but eat her out of house and home and you may just get your marching orders.
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« Reply #4 on: November 10, 2008, 12:08:14 PM »

Thanks for the advice bike
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