Gas vs wood fuel technical question

[Aunt Maud]

Just had a thought whilst trying to go to sleep 

Have a look at Leca, which is an expanded clay aggregate that's used for insulating limecrete floors, growing medium for green roofs and loads of other stuff. My walls are insulated with 300mm of it behind lath and plaster and I've filled the void under the suspended timber floors too. It absorbs a bit of moisture but dries out quick and doesn't ever change in hardness.

Your chimney guy may not have heard of it, but thinking about it a bit, I'd use that instead of Vermiculite in a damp chimney as a fill.

[Mrs Pingu]

Ta.

[Mrs Pingu]

Well, my brother's stove installer is coming for a look tomorrow. I spent some free time this week reading the wood burning geek section of the Green Living forum and today having a hard look. I think it's possibly going to be a Morso 04, a Charnwood C4 or the Defra Sqrl, unless he says any of them aren't going to fit.

My brain freaking hurts nao.

[Aunt Maud]

The Morsø Ø4 looks nice.

Dad's got a small one like that and it's a really lovely stove.

[Mrs Pingu]

Clearview Pioneer was heavily recommended but it's the most expensive of the lot and apparently not the best customer service so I discounted hat one already.

I looked at the Morso O4 instructions, and they are *very* extensive, though I must admit they scared me off a wee bit!

[Aunt Maud]

They use a Norwegian developed method of lighting, where you put the logs at the bottom and light the kindling on the top. It means that, as wood contains a huge amount of combustible gas, more of the gas gets burnt off at start up instead of it just flowing up the flue and adding to the pollution. You need a fair amount of kindling for that though, but once you get the hang of it, it works really well as you don't need to put cold logs on kindling to get a fire going and end up filling the house with smoke.

I think the key to getting Morsø stoves or any other stove going really well, is to use properly seasoned wood (any wood, btw), putting a couple of bits in et each fuelling and allowing a fairly thick 2-3cm bed of embers to build up during the firing. Using smaller bits of firewood works much better and gives better heat than a single great lump.

At the end of the day I don't put any more wood on to try and get it to burn through the night, but close the air vent down (but not off) when the wood has turned to glowing charcoal. In the morning the stove is still lukewarm and there's still embers in the ash that I use to start a fire in the morning before we all go out for the day. You need a blowpipe for that, mine's a bit of copper tube about 2' long.

Living in a thatched timber house, the last thing I need it a chimney fire during the night and fuelling up and closing off the vent before bedtime is a really good way of coating the flue with tar, which can lead to a violent chimney fire and burn the house down.

I like a fire, just incase you were wondering.

I've heard that you can get Spruce and Larch up your way for pennies, as they can't sell it for some reason.

[Little Jim]

I've heard that you can get Spruce and Larch up your way for pennies, as they can't sell it for some reason.

The chap that sold me our stove (a Jotul F100 which is brilliant) warned me off using soft wood as he said it gave off a lot more tar than hard wood and cited a local farmer he goes to every three or four years to renew the chimney liner as the chap only burns old pallets.  I've often wondered how true this is as it is much easier to get hold of soft wood, and in Scandinavia they all seem to burn just softwood with a bit of birch on their stoves.

[P Walsh]

If you want to keep the flue clean the best thing to do is run the fire really hot every now and then, rather than just ticking over.

[Little Jim]

Will that get the flue hot enough at the top to get rid of the tar? - I assume that the hear causes the tar to vaporise.

[Aunt Maud]

Softwood does contain a lot of tar, so does Birch bark and it's extracted on a commercial basis in Sweden and Norway. But the key to a wood burner is having the air always fully open when your firing, so that it gets burnt off in the stove along with the gas, by the high heat you end up firing at. If you're worried about it mix woods together, but high heat using seasoned wood is the way to burn cleanly.

Having the air fully open all the time and controlling the heat output with the quantity, type and size of wood is something I've been doing for a while and I've found that it keeps the glass clean on my Morsø 3440, which is a tricky burner to use. I sweep out the pipe connecting the burner to the chimney flue regularly, as this keeps the heat output of the burner high. A 2mm layer of dry soot in the pipe reduces the heat output greatly, as it acts as an insulator. I burn a lot of wood though and went through about 20 cubic meters last year.

If you've got a metal flue liner, which we had in our old house, the liner expands enough when it gets hot to break the soot/tar layer off, but we didn't have vermiculite in the chimney and the pipe vibrated alarmingly when the burner really got going.

As for pallets, I don't think they use seasoned wood to make them with, so the guy might be burning wood with a high moisture content which has a low heat output.

[Mrs Pingu]

Stove dude has been, discussed the dog leg in the flue (the fireplace has obviously been moved) and whether to move it back or not (not, cos I don't want to lay new carpet as well, and it would be in a really odd place), laughed at the vermiculite & mortar idea and the extortionate first quote ("Ten grand Dan" was his quip so it sounds like I got away lightly with 5).

He said all the stoves on my list were do-able and good so we agreed he's gonna quote for a Squirrel

[Mrs Pingu]

I've heard that you can get Spruce and Larch up your way for pennies, as they can't sell it for some reason.

http://www.flamingfires.co.uk/which-wood-burns-best.htm ?

[P Walsh]

I've heard that you can get Spruce and Larch up your way for pennies, as they can't sell it for some reason.

http://www.flamingfires.co.uk/which-wood-burns-best.htm ?

I disagree with some of those assessments. For example, willow, properly seasoned, burns really well. Oak, split with a hatchet to pieces with a cross section of about 3cm, is a sort of super-kindling, igniting quite quickly, rapidly reaching a high temperature, and sustaining much longer than the more usual softwood kindling.

I haven't used a lot of larch, though. I have always used spare pallets as a source of kindling with no problems.

[Aunt Maud]

 I've seen that list before, too.

It puts Holly as poor, but it has the highest kWh heat output of common Northern European fire woods, according to The Norwegian Forest and Landscape Institute. ( The Norwegians do the testing for EN certified stoves and they clearly know their wood from their trees, meh!)

And its write up of Oak is hokum, they must have been on the loony soup when they tested that one.

[rogerzilla]

A Badger has a much bigger firebox - think convenience - than a Squirrel, for similar nominal output (about 5kW).  My Badger heats a whole  3 bed semi quite easily, although it is reasonably well insulated and has outside air (no sucking cold combustion air into the house - absolutely worth it).

[P Walsh]

A Badger has a much bigger firebox - think convenience - than a Squirrel, for similar nominal output (about 5kW).  My Badger heats a whole  3 bed semi quite easily, although it is reasonably well insulated and has outside air (no sucking cold combustion air into the house - absolutely worth it).

It is usually considered more efficient to run a low kw stove at a high output than a high kw stove at low output, so getting too large a stove could lead to less heat from your wood, and more smoke. It's worth doing the maths. My Clearview (4kw, I think) heats the whole house a bit, but on really cold days we do need the gas central heating as well.

[pcolbeck]

They use a Norwegian developed method of lighting, where you put the logs at the bottom and light the kindling on the top. It means that, as wood contains a huge amount of combustible gas, more of the gas gets burnt off at start up instead of it just flowing up the flue and adding to the pollution. You need a fair amount of kindling for that though, but once you get the hang of it, it works really well as you don't need to put cold logs on kindling to get a fire going and end up filling the house with smoke.

Our Dunsley Yorkshire stove has a double burn. It passes the gas back over the fire so it burns it off before it goes up the flue. Mind you it's a 15kw stove so too big for most uses, it has a back-boiler though so at least 50% of that heat goes to the heat store and thus to the radiators or to provide hot water for showers and baths.
Maybe their smaller stoves also do reburning of gas ?

[P Walsh]

They use a Norwegian developed method of lighting, where you put the logs at the bottom and light the kindling on the top. It means that, as wood contains a huge amount of combustible gas, more of the gas gets burnt off at start up instead of it just flowing up the flue and adding to the pollution. You need a fair amount of kindling for that though, but once you get the hang of it, it works really well as you don't need to put cold logs on kindling to get a fire going and end up filling the house with smoke.

Our Dunsley Yorkshire stove has a double burn. It passes the gas back over the fire so it burns it off before it goes up the flue. Mind you it's a 15kw stove so too big for most uses, it has a back-boiler though so at least 50% of that heat goes to the heat store and thus to the radiators or to provide hot water for showers and baths.
Maybe their smaller stoves also do reburning of gas ?

I think Clearview were one of the first to use this secondary burning using pre-heated air, but it is quite common now. It produces more heat, less smoke and clearer glass.

[Aunt Maud]

They use a Norwegian developed method of lighting, where you put the logs at the bottom and light the kindling on the top. It means that, as wood contains a huge amount of combustible gas, more of the gas gets burnt off at start up instead of it just flowing up the flue and adding to the pollution. You need a fair amount of kindling for that though, but once you get the hang of it, it works really well as you don't need to put cold logs on kindling to get a fire going and end up filling the house with smoke.

Our Dunsley Yorkshire stove has a double burn. It passes the gas back over the fire so it burns it off before it goes up the flue. Mind you it's a 15kw stove so too big for most uses, it has a back-boiler though so at least 50% of that heat goes to the heat store and thus to the radiators or to provide hot water for showers and baths.
Maybe their smaller stoves also do reburning of gas ?

Been looking at getting a stove with a back boiler, how big is your hot water tank ?

[pcolbeck]

They use a Norwegian developed method of lighting, where you put the logs at the bottom and light the kindling on the top. It means that, as wood contains a huge amount of combustible gas, more of the gas gets burnt off at start up instead of it just flowing up the flue and adding to the pollution. You need a fair amount of kindling for that though, but once you get the hang of it, it works really well as you don't need to put cold logs on kindling to get a fire going and end up filling the house with smoke.

Our Dunsley Yorkshire stove has a double burn. It passes the gas back over the fire so it burns it off before it goes up the flue. Mind you it's a 15kw stove so too big for most uses, it has a back-boiler though so at least 50% of that heat goes to the heat store and thus to the radiators or to provide hot water for showers and baths.
Maybe their smaller stoves also do reburning of gas ?

Been looking at getting a stove with a back boiler, how big is your hot water tank ?

300 litres. Heated by the back boiler and an oil boiler. It also has a loop for solar hot water that I haven't got round to buying yet and ports for an electric immersion heater (not fitted).
Run the stove full blast all day and it can get this up to 85 deg C even on a cold day. The stove is auto damping though if you close the vents so you can avoid this at the cost of a sootier burn.

Domestic hot water is mains pressure via a plate heat exchanger on the heat store and the central heating pumps the 300 litres round the radiators.

[Mrs Pingu]

I found the Woodburning subforum of this place full of useful information : http://www.thegreenlivingforum.net/forum/index.php

[rogerzilla]

A Badger has a much bigger firebox - think convenience - than a Squirrel, for similar nominal output (about 5kW).  My Badger heats a whole  3 bed semi quite easily, although it is reasonably well insulated and has outside air (no sucking cold combustion air into the house - absolutely worth it).

It is usually considered more efficient to run a low kw stove at a high output than a high kw stove at low output, so getting too large a stove could lead to less heat from your wood, and more smoke. It's worth doing the maths. My Clearview (4kw, I think) heats the whole house a bit, but on really cold days we do need the gas central heating as well.

Yebbut the Squirrel and the Badger are basically the same nominal output, as I said.

The Badger works quite differently; the secondary (and tertiary) air is pre-heated and drawn in through holes in the baffle plate.  The Squirrel is a very traditional design and just draws in secondary air from the upper door vent.  The Badger needs a bigger firebox for all the gases to burn efficiently and this also means you can fit bigger pieces of wood in there, which means less chopping and sawing.  It doesn't mean you should actually load it up to the baffle plate and if you do it will tend to over-burn unless you reslly shut down the air, which is not ideal as it mucks up the glass.  I use a Morso flue gas thermometer and keep it in the "ideal" zone, although how accurate it is, I don't know.

[Feanor]

A wee tip regarding tarred-up glass on woodburners...

The asphaltine-ish tarry residue that builds up on the inside of the glass of a wood burner over the course of time can be difficult to remove.
As has been covered already in this thread, this can be minimised by keeping the burn temperature up.
But there is always a sooty burn period as the thing starts up.

But it's nice to have the glass clean.
I initially tried all the usual glass cleaners and domestic solvents.
None of them were of any use.
Mechanical scrubbing was useless too.

Solution:
Muck-Off pink stuff bike-cleaner = totally excellent.
A world apart from any of the other cleaning products I had to hand.
It actually worked as a solvent for the residue.
Quick spray, leave for 1 minute, then mild mechanical scrub with a scotch-brite pan scourer ( one of those things that are a sponge on one side, and a plasticky scourer on the other) and it's like new.
Wipe the black liquefied yuck off with a paper towel, rinse and repeat if required.

[Aunt Maud]

Second vote for a large fire box. I've got one of the cylindrical Morsø burners too and the box is too small, which is a royal pain in the butt, it does burn really well though.

[Mrs Pingu]

I've read that you can use a bit of the ash on some damp paper to clean the glass, but if that doesn't work I'll know to try Muc-Off.
When I eventually get the thing that is, still waiting on the quote....it will be summer by this rate and I won't want the thing on.