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Recommended bio mass boiler ?

 
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Barney



Joined: 08 Aug 2013
Posts: 2

PostPosted: Thu Aug 08, 2013 9:38 am    Post subject: Recommended bio mass boiler ? Reply with quote

Hello,
Firstly please let me say hello as im new here.
I am converting a large barn into a family home.We are off Gas but have electricity.Time has come to decide on a way of providing heat and hot water.
Bio mass seems to be the way to go but I favor a multi fuel system.
I see a lot of boilers for sale on E bay but have no idea if there any good.
Does anyone have experience of a boiler they could recommend ?
I need a minimum of 35 kw.

Many thanks, Barney.
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clv101
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PostPosted: Thu Aug 08, 2013 10:07 am    Post subject: Reply with quote

Hi Barney, and welcome.
I can't personally help with the boiler, but I would say 35kw is a lot! More investment at this stage on insulation would be a wise move. Also give some serious thought to solar thermal. The recently announced Renewable Heat Incentive tariffs for solar thermal are very generous.
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adam2
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PostPosted: Thu Aug 08, 2013 12:34 pm    Post subject: Reply with quote

Yes, 35KW is a lot ! even basic insulation should halve that, and good insulation reduce it still more.

I would think twice about too much high technology such as wood pellet boilers, expensive, complicated, and potentialy unreliable.

I would suggest a modest sized log burning stove that heats radiators, most suppliers of such state how many radiators can be supplied.
Many more can be connected if desired, provided that they are small ones such that the total radiating surface is within the capabilities of the stove.
Very small radiators will heat well insulated spaces.

I would seek the advice of a reputable dealer in solid fuel appliances, not IMHO something to be purchased on fleabay.

It would be well to select an appliance that can also burn coal.
Renewably sourced wood is far preferable to coal which is a carbon intensive fuel and best avoided normally.
However a couple of tons of coal is a reassuring thing to have stored in case logs are in short supply.
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PS_RalphW



Joined: 24 Nov 2005
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Location: Cambridge

PostPosted: Thu Aug 08, 2013 12:51 pm    Post subject: Reply with quote

Similarly I am looking at insulation first and foremost for my 'new' house. I would love to dump the 25KW inefficient oil fired boiler, but the more I insulate, the smaller the replacement boiler will need to be. Then I can consider linking in a woodburning stove to the existing radiators, but I am limited in the size I can fit by the thatched roof and insurance requirements, which combined with the listed status and conservation area status, makes progress difficult - the insurance and listed building regulations are incompatible, and solar hot water almost a non-starter.
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woodburner



Joined: 06 Apr 2009
Posts: 3384

PostPosted: Thu Aug 08, 2013 7:24 pm    Post subject: Reply with quote

Having a tiny bit of experience here, 35kW is not a lot for a bio-mass boiler, and you get a bigger handout for larger boilers. Wood pellet means you need processed fuel, as does wood chip. log means you need less processed fuel, but it isn't easy to automate handling. The installation cost will be huge by most peoples standards. You can easily spend 15k.

A dry woodburning stove is much more flexible. For a boiler Frolinger boilers are one reputable brand, but there are others. Don't do your research on Internet forums, you need to get some engineering guys in and investigate thoroughly or you will be parted from your money and still left with a problem.

The market is not well developed in the UK for domestic setups.
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kenneal - lagger
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Joined: 20 Sep 2006
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PostPosted: Fri Aug 09, 2013 2:06 am    Post subject: Reply with quote

I've recently designed an insulation installation for a 158m2 1970s house and reduced their heating costs by 82%. That's his actual savings on his bills from before the installation. The levels of insulation which were installed were about those which will be required from 2016.

Last winter he only ran his gas central heating on one day. The rest of the time he relies on a 7kW woodburner. His installation cost him about 30K which came from his pension lump sum and he's getting a better rate of return on his investment than if he had bought an annuity with that money. His home is also more comfortable.

What you have to realise, Barney, is that in future wood will not be a cheap source of energy. As more and more people get on the bandwaggon wood will become as expensive as, or even more so than, oil or electricity if people keep putting huge boilers into inefficient houses. It will also become more difficult to source.

Insulation, and it's friend airtightness, are a one off expense. It might seem expensive now but fuel is now cheap compared to what it will cost in the future. Even if we get large supplies of shale gas the price of gas will not go down as the cost of extracting the shale gas demands current gas prices to be economic. Gas is also an international market and its one in which demand is increasing worldwide at a greater rate than supply. Hence prices will rise.

You are starting with a basic shell so you can install insulation much easier and therefore much cheaper than a retrofit. You are building something that should last for hundreds of years. Don't you owe it to future generations, if not yourself, to build something that will be fit for purpose in ten years time let alone a hundred.

We heat our 180m2 cob built house with a 20kW Wamsler cooker and a 7kW woodburning stove although we rarely have both on at the same time. We use from 6 to 8 tonnes of logs a year about half of which is softwood and half hardwood. We get the softwood quite cheaply at about 10 per tonne but we process that ourselves. The hardwood we get mostly free but we have to cut it, transport it and process it ourselves. We are going to insulate the house externally in an effort to reduce the amount of wood we burn as my back is not getting any younger and for the reasons quoted above about security of supply. If you buy in logs you will be looking at at least 60 per tonne and that has probably doubled in the last few years.

Please insulate it properly before you look at which boiler to install. Don't tell us that you have insulated to the Building Regulations requirement because that is inadequate. The government have more or less admitted that fact by saying that they will require "Zero Carbon" houses in two years time. The only way to build zero carbon houses is to drastically increase the levels of insulation installed from those currently required.

If your architect hasn't advised you to increase the insulation levels above the minimum required he is incompetent as, sadly, most of the architectural profession are. They were trained in an age when fuel was cheap and global warming hadn't been recognised and most haven't bothered to keep up with modern conditions and requirements. Sadly the education standards for new architects aren't much better as most only get training in sustainable architecture at post graduate level. Sustainability in architecture needs to be the first thing that is considered not the last.

There are a few good architects around, and we have one on this board, but for the majority sustainability is an afterthought, if they even get around to thinking about it.

If you want a damp, draughty, uncomfortable, expensive to heat home go ahead and install your 35kW boiler. If you want affordable, draught and damp free comfort insulate your house properly and go for a much smaller boiler. If you install the 35kW boiler don't put any cupboards or wardrobes on the outside walls because you will get mould growth in or behind them. Be prepared for mould growth on your decoration especially in the corners of bedrooms and other upstairs rooms. Just warning you!

Rant over.
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Barney



Joined: 08 Aug 2013
Posts: 2

PostPosted: Fri Aug 09, 2013 2:26 pm    Post subject: Reply with quote

Thank you for the informative responses. A bit more info.
The volume of the barn is 687 m 3. I have put 25 mm king span on top of the roof joists,80 mm in-between and 80 inside. The walls will be stud work inside with at least 100 mm insulation. The floors I have laid have 120 mm king span under the concrete. I will use vapour barrier to seal any drafts before plaster board. I intend to put 100mm between the floor joists.

I had a renewable energy firm into quote and they came up with the 35kw size boiler. Do I need more insulation than this ?

I also have permission for 3 log/multi fuel stoves. I have one which has a back boiler and overall rating is 14 kw.If I did collect heat from all 3 stoves for water and heating what would I do for hot water in the summer ?
An immersion heater ?
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emordnilap



Joined: 05 Sep 2007
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PostPosted: Fri Aug 09, 2013 2:50 pm    Post subject: Reply with quote

We have an immersion heater for back-up hot water in the summer and, providing it's only used precisely when needed, it's terrifically handy; I recommend you use a 100% renewable energy supplier.

Solar hot water panels are essential; every south-facing roof should automatically have one included - surely someone can come up with ways of blending them in on listed buildings?

Consider SolarTwin - a panel which works when the grid is down and consider over-sizing it with a large cylinder. I wish we'd gone for a larger panel but there you go. SolarTwin works for us really well but you have to change your hot water usage habits to make the most of it.
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kenneal - lagger
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PostPosted: Sat Aug 10, 2013 2:35 am    Post subject: Reply with quote

For an optimum level of insulation i.e. one that will not be found to be inadequate in a few years time, you should be looking at 300 of PIR foam (450 fibre insulation) in the roof, 200 PIR insulation in the walls (300 fibre) and 200 PIR under the floor (300 Polystyrene) with high quality double glazed or preferably triple glazed windows. You will need 100 of fibrous insulation of at least 30kg/m2 density under the first floor to provide the required sound insulation. The levels of insulation that you are providing will give you the current Building Regulations requirement only which will be inadequate in 2 years time.

The detailing to ensure no cold bridging and air tightness is most important and is beyond the competence of anyone but a specialist. A failure in this area will negate the insulation for up to a metre either size of the gap. It 's that important!

Most log burning stoves that have a boiler in them have a very low efficiency because the boiler is usually situated in the fire box and lowers the firebox temperature so that the burn is not clean. If you have one wood burning stove with a back boiler, or preferably one with the boiler outside the firebox, you will not need a boiler in the other stoves. The stove will heat the room without the need for central heating. You only need one stove, or preferably a separate boiler, to provide your domestic hot water.

Solar hot water of the correct size will give you all you want when the sun is shining but in a year like last year you will not get much at all. You need some form of backup and in a lightweight structure such as yours, if properly insulated, it will preferably be one that doesn't put too much heat into the house. A dedicated cooker or boiler will restrict the amount of heat that goes into the room or a stove with a back boiler in a room with good ventilation would work. The outside alternative would be an electric immersion heater.

I have had a Solartwin hot water panel and now use evacuated tubes which I find to be more efficient. The Solartwin would not start working until about 11:00 in the morning and would stop working about 4:00 in the afternoon whereas the evacuated tubes work from 9:00 until about 6:00 in high summer, given sunshine. I bought the Solartwin system because we were off grid and didn't have constant electricity during the day. It was the only system that worked in those circumstances. We now have a battery system with an inverter to provide us with constant electricity so we have moved on to a more overall efficient system.

The size of system will be determined by the number of people served and whether or not you are economical with your precious hot water. Given the volume of the house and the number of people that could be accommodated at a rough gues I would have thought that you would need two Solartwin panels or a 36 or 48 tube array.
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Tarrel



Joined: 29 Nov 2011
Posts: 2447
Location: Ross-shire, Scotland

PostPosted: Sun Aug 11, 2013 6:46 pm    Post subject: Reply with quote

Barney, it would be interesting to know where you plan to source your fuel from. There are batch-burning boilers that will burn a whole mixture of wood; logs, offcuts, brash, etc. They tend to be higher power, but you only run one "burn" per day, feeding the energy into a large thermal store, which then drives your heating and hot water, and can be supplemented by solar thermal.

Bear in mind a 35kW boiler will be using upwards of 100kg of logs a day if you run it for, say, 10 hours.

Agree with the other posters on insulation. We moved into an old listed cottage in Scotland 18 months ago. Insulation went from "something we ought to do on principle" to an absolute priority as soon as the winter kicked in! The basic principle we learned was; you need more than you think.
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