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UK's most popular Renewable Energy Forum October 25, 2014, 11:45:49 PM *
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Author Topic: HIgh level chimney heat recovery  (Read 4944 times)
Capcave
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« on: November 25, 2008, 11:25:15 AM »

There have been loads of posts in the past about recovering heat from the chimney of a wood stove from within the house. However the need to avoid tar build up would tend to suggest that this is best avoided. However with 2 inches of snow outside I can help noticing the heat haze coming out the top of my stack with mild dismay having cut the wood. Would it not be pratical to construct a heat exchanger into the chimney cap that extracts most of the heat above the masonary that makes up the stack? It would be the sort of thing that you would need to remove annually to clean all the tar off (acid bath of some sort?). Maybe I'll bodge something up with some copper coil and vermiculite and see what comes out of it. Smiley
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Billy
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« Reply #1 on: November 25, 2008, 11:55:49 AM »

Hi,

Stick a thermometer up there and check how hot it is first.  You can get a nice haze from very little heat if it's cold outside.  I only say because I had to sort out some tiles near my old chimney, winter, woodstove was going and I thought I would warm me hands up.  I was surprised how not hot it was.

We had a ss liner up to the cap but it was not  back filled so I guess the fire is pretty efficient and the rest heated up the air space outside the liner.

Just a thought

Smiley Smiley
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24v Rolls @458ah C5, Victron Multi 3kw, Yingli 880w MPPT PV, Morso Squirrel, Lombardini 6LD 24vdc genny, Compost dry toilet.
dhaslam
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« Reply #2 on: November 25, 2008, 02:59:18 PM »

I have a problem with the chimney being too hot.  Even though the heat at the stove is in the range 200-300C the blockwork around the flue all the way up is very hot, about 55C.   The problem is that the plaster is cracking both vertically and horizontally.    The builder is putting  a filler in the cracks but the chimney may need to be lined.   A thermostatically controlled heat exchanger to air would be very useful but it would have needed to have been built into the chimney.    The temperature could be controlled down to about 150C without affecting the normal operation.   I have heat recovery ventilation which could distribute the heat all around the house by heating incoming air. 
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DHW 250 litre cylinder  60 X 47mm tubes
Heating  180,000 litre straw insulated seasonal store, 90X58mm tubes, 1 kW VAWT, 3 kW heatpump plus Walltherm gasifying stove
wookey
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« Reply #3 on: November 27, 2008, 06:32:33 PM »

Off-topic for the thread...

gah - who showed people how to do silly scrolling sigs? I can nobble all the dancing 'smileys' in my browser but the scrolling sigs keep scrolling in a very distracting fashion. I can't stop it without disabling javascript completely for the forum via noscript (which probably breaks some useful functionality)

Please don't do it. Some of us hate it, and it's difficult to neutralise.

Now back to your normall programming
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Wookey
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« Reply #4 on: November 30, 2008, 11:29:28 AM »

The two smiley faces sliding across my screen higher up in this thread?
Lucky no-ones using that 'insect crawling about' avatar - I've seen my wife pick at the screen to get the bug off it when she's seen that.
Oh, and have a  bike
 stir
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