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Wood Chaudiere


Gyn_Paul
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I am just about to start installing a huge, very ancient log-burning boiler which will run in tendem with an existing oil guzzler. Eventually - when the funds have recovered a bit - I'll change it for a gassification boiler and an accu of 2k litres or so. But just at the moment the emphasis is on getting the place heated by something which isn't costing 72c/litre!

So, this boiler has a horizontal flue of 160mm diam. (or therabouts) and will be sited on the end (apex) wall in the barn. Rather than faff about with the timbers and tiles at the ridge, I propose to run the flue through the wall and up the outside. Building for it a chimney of the thinnest parpangs insulated with rockwool (which will work out cheaper than using the square, 30cm terracotta chimney sections, and not in the same league as twin-wall stainless tube, which - for the 7.5 metres height required - costs much the same as a medium-sized family car.

What I should like to do is take the flue vertically a metre or so, (after a straight 'T') then to a 45 degree elbow, throught the wall, then to a 45 degree 'T' , then upwards to the top in flexi. Obviously, the 'T's are to allow access to sweep the chimney sections.

My problem is I don't seem to be able to find a 45 degree 'T', so I'm faced with either 2 x 45 degree elbows, and no cleaning access. Or starting the flue with the better part of a metre (50 cm of wall + spacing on each side) of horizontal piping.

Which, do you suppose, would be the lesser of these two evils?

p

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[quote user="Gyn_Paul"]But seriously, will 1 m horizontal, then 7 m vertical flue give sufficient draw?

p

[/quote]

Here you are GP: Calculate from this:

See here:

The most critical factor is the temp difference: since you are insulating well with Rockwool, that will create a significant natural draft.

Pipe diameter also comes into the equation: venturi effect.

See also Here:

In point of fact, whilst people believe the longer the chimney the better the draft, as it says in Porgi and Bess "It aint necessarily so!"

For example, examine a basic blacksmith's forge: very short chimney pipe normally.

P.S. Like the forward concept for the gasification boiler and the thermal store: way to go!

Me too, shortly.

Renewable: greenish; subsidised.

Can't be all bad!

[:)]

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[quote user="Gluestick"][quote user="Gyn_Paul"]But seriously, will 1 m horizontal, then 7 m vertical flue give sufficient draw?

p

[/quote]

Here you are GP: Calculate from this:

See here:

The most critical factor is the temp difference: since you are insulating well with Rockwool, that will create a significant natural draft.

Pipe diameter also comes into the equation: venturi effect.

See also Here:

In point of fact, whilst people believe the longer the chimney the better the draft, as it says in Porgi and Bess "It aint necessarily so!"

For example, examine a basic blacksmith's forge: very short chimney pipe normally.

P.S. Like the forward concept for the gasification boiler and the thermal store: way to go!

Me too, shortly.

Renewable: greenish; subsidised.

Can't be all bad!

[:)]

[/quote]

Thank you for that - I think - my head hurts now!

Gassification boiler...Do you have an actual boiler/manufacturer in mind yet? I'm looking at Atmos, but it seems you can't buy directly from them anymore. drat, missed the chance as usual!

p

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I haven't actually decided on a manufacturer as yet: nor a specific model.

They do vary from the most amazingly complex (particularly Swedish examples) and expensive, to basic bits of kit which should do the job satisfactorily.

Hard to obtain prices on most, for some obscure reason.

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They are great bits of kit but what to put in the fireplace, surely not the ugly gasification boiler? I saw some very efficient wood burners recently in the gasification sense but they were also styled around modern woodburner looks with convection fans built in.
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The idea, T, is to site the gasification boiler and the thermal store in the dependence.

Mine, eventually, will reside in the barn which is now the garage.

Nothing preventing a nice insert or Pôele de Bois sitting in the fireplace as a focal point and for extra warmth on Winter evenings.

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Yes different function, different form.

~Stylish poele stacked with logs, choked down to practically nothing, lazy flames licking round the logs for the whole evening

Vs

~Ugly cast-iron box roaring fan assistedly through charge of wood in an hour or so, extracting practically all of the calorific value available in one short continuous blast and transferring it to big tank of water.

I know which one I want to heat the house, and which one I'd rather toast my toes in front of!

p

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Gyn Paul, no not the lazy poele, new generation of wood burning fires also extracting nearly all of the calorific value throgh gasification technology but appearing as a wood burner for the lounge. I have some information somewhere, maybe I can point you to a website later.
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Trouble seems to be, T, that if one needs a certain minimum puissance in order to impart sufficient heat energy into a building space such as a home, the sheer size of the average insert or free-standing pôele able to release sufficient heat energy is simply too big.

I'm also marginally cynical about some claims for thermal stores: rough calcs indicate to me sizes rather larger for a daily single continuous burn.

Similar to electric storage heaters in the UK years ago: we had one house thus equipped,  almost new installation when we bought it.

Great on cold Winter mornings: but dire by 4.00 PM: and these were big ones, too.

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