Stoner – Yes jealous but don’t have the space to do such a venture which is the problem for most people. Plus the money.
Thermal Stores aren’t for everybody either due to long heat build up times but if you can live with that after a holiday then it’s no issue really. Problem is most people can’t.
You’ve got a wood option though so the pellet side is a nice option to have as a backup/lazy option. What is it? Is it one unit or 2 separate boilers?

I don’t come across this from a green angle, I am only interested if it saves money, albeit with subsidy. None of this stuff will truly take off unless it can be shown to do this.

Indeed that’s how I view most of this stuff but it’s getting forced on new build now too which will drive prices down and technology up. Hopefully.
Although I like log boilers and if I were doing this house again I’d consider one in the garage linked something else. Might even be a high temp air source unit as it’s a 70s house but I can live with underheating then put a stove in rather than one with a back boiler which does work mind. The electric boiler we have on top of the stove is an expensive early morning and keeping the house above freezing during holidays luxury.

From a monetary point of view I’d stick with Mains Gas still for quite a while longer if you can get it (and while you still can). Tech and knowledge will get better and prices cheaper.

From a monetary point of view I’d stick with Mains Gas still for quite a while longer

absolutely.

Here’s mine, although slightly different now, as there’s a solar thermal circuit Ive stuck in with a header tank.:

Augured pellet feed to the right, log furnace to the left. Both heat the same water. A burn gives about 50kWh of energy, a bag of pelltes has about 50kWh of energy in them. Peak consumption in the middle of a cold winter is about 150-200kWh a day. My solar thermal provides around 50-60kWh a day which is my DHW requirement.

This is last year’s fuel consumption and then with the solar thermal installed. This year’s is much smoother but I havent enough data for a decent graph yet.

As above though, I also take the economics as the lead, rather than the bunny-hugging.

As above though, I also take the economics as the lead, rather than the bunny-hugging.

I’m going to call you on that one.
It’s really all about playing with the big hunk of metal and fire.

That is a lovely looking compact unit and set up for the pellets.

WANT

its quite an involved system. You do have to work with it, its not for little old ladies to turn on and forget.

There is some dark art to getting the furnace burn right, and getting a feel for when the boiler is sooting and needs a clean and a service. But I can do it all myself (including repairs or part replacements) which saves money, but again adds to the involvement.

I currently feed it on 10Kg bags of pellets, but I dont like the waste of all the plastic bags it comes in and the delivery cant deliver the pallet direct to my store. So once Ive gone through the last tonne in spring, Im going to build plywood tank for about 2-3 tonnes blown bulk delivery with a hatch on it and manhandle 30Kg at a time into the “week store” that you can see above in a wheeled bucket. My store is only 15m from the tank.

So Stoner do you reckon your setup is cheaper than oil to run? Our oil boiler is getting pretty old now (25 years, but still running OK) and we’re going to have to replace it at some point.
We have plenty of outbuilding space that we could put a biomass boiler in along with a big hopper for blown bulk delivery.
The main issue is that the building it would go in is about 30m from the main bit of the house – could the flow/return pipes be run that sort of distance through a suitably insulated duct?

sharkbait,

Im pretty sure mine is cheaper than oil now, although when I did the original sums when I was specifying it, it was, on paper, going to be a bit more expensive in the short term, but oil price inflation has already taken oil ahead of biomass since then, only 2 years ago.

Last figures I worked out are here:
http://singletrackworld.com/forum/topic/biomasssolar-eco-experts-advice-sought-stoner#post-2959506

if you use the average kWh consumption figure and british gas tarif structures, the weighted average cost of gas fuel is about 4.9p/kWh. At 90% efficiency for an A rated combi, that’s a real heat generation cost of about 5.5p/kWh

My pellets cost about £259/tonne, with an energy density of about 4.9kWh per Kg, 5.2p/kWh
At 89% efficiency in my pellet boiler, thats 5.8p/kWh.

With heating oil prices at around £300/500 litres and oil energy density of 10kWh/litre, oil boilers are a little more efficient at around 92%, so cost comes out at 6.5p/kWh

Those calcs rather surprise me. When I first did these figures 18 months ago, gas was loads cheaper, and oil was the second cheapest – something like 3.5p gas, 4.4p Oil and 5.5p wood.

What I missed out from that calc is the log cost. If I burn logs, my finger in the air estimate is that it costs me around 3.5-4p/kWh.

30m is quite a way, but my neighbour has his biomass boiler in an outhouse about 10m from his scullery where the pipes come into the house and distribution manifold. I saw him install the insulated pipe work and it’s big stuff, something like 75mm thick (160mm+ dia) of armourflex insulation around a 28mm flow and return, in a plastic conduit. Not cheap stuff but Im assuming it’s got excellent thermal characteristics.

The capital cost of my install was about £10k for the boiler and thermal store and another £2k for the solar thermal that did myself. I currently do not have any RHI payments becuase my particular boiler does not have MCS certification. This is because there’s some uncertainty on how the govt want to treat log boiler efficiencies. You can more easily find certificated pellet boilers (the pelletmaster by woodviking is the sister unit of my big biotriplex thing and is certified) and that would give you an RHI income to offset the capital expense.

You dont necessarily need a thermal store, it just makes addition of solar thermal easier. If you were just going to use the pellet boiler all year round you could rely upon the tank in the boiler alone.
https://sites.google.com/site/woodviking2010/pelletmaster

the pelletmaster has a 220L tank and an indirect coil in it so you can use it for potable indirect DHW and as well as radiators and UFH if you have it. That boiler is about 5-6k + installation cost. You’ll need to research how much the RHI might be worth I havent done it for ages.

If you’re interested in the woodviking models, Id be happy to introduce you to a very excellent installer based in the south west, or the UK rep who I know quite well.

There are plenty of plastic underground heating mains available which are pre insulated.
Uponor springs to mind.

The life span quoted for them worsens the higher the temperature you put through them and if you can do it in a full length with no fittings underground is a better solution. Note “quoted”

I wouldn’t even entertain metal pipes underground however well protected but I know there are welded systems out there that work fine.