wood burning stoves

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Re: wood burning stoves

Postby GeoffHammond » Fri May 20, 2011 4:18 pm

We have a two-flat-panel solar collector for our hot water and the only backup is from the wood burner. It has a jacketed flue for heating water. I don't believe a jacketed flue gets as much heat into the water as a wet-back does. I think it also means I have to get an amount of hot exhaust moving up the chimney to heat the water and that sometimes the fire needed to achieve that amount will be more than I need to heat the room.

We're only two people, but sometimes I wonder if I should buy a LPG instantaneous water heater for those few days in the year when I want something more...

I've found that my black wattle burns okay. My yellow box burns okay. What's known as blackwood around here is not real special. If only I had my own forest of river red gum, bastard box and ironbark... Each species seems to have its optimal seasoning time, I think, as well as a gaggle of other positive/negative aspects. I prefer to cut the wattle wet and the box dry, to get the balance of chain-dulling and saw-clogging right.
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Re: wood burning stoves

Postby cw nsw » Fri May 20, 2011 4:34 pm

mog, I just googled a bit & quickly found the bakers oven ref for mearnsii in one of the links below, probably also applicable for the similar decurrens.

these govt websites reckon that they are fine for firewood - guess it depends on how much elbow grease you are prepared to put in, or in my case, what I paid for someone to cut my timber for me. :)

in that case, many moons ago, it was cheaper to buy ironbark which gave much more consistent heat and by volume probably lasted about 4 times as long.

http://new.dpi.vic.gov.au/forestry/fore ... m-forestry

http://outernode.pir.sa.gov.au/forestry ... _australia

elsewhere people have commented that some 'experts' don't recommend burning wattle in fireboxes.
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Re: wood burning stoves

Postby mog » Fri May 20, 2011 11:05 pm

Thanks for that, CW - very useful sites as well (Mr.Google can be so helpful!). A. mearnsii really does grow almost like a weed around us, so that's probably why people use it for firewood there's so much more of it than anything else! The same guy who told me about baker's wood also said that you could only burn it 50/50 in a wood burning stove with some other hardwood.
And thanks, Geoff, for the wood-cutting tips - I shall pass them on to chain saw operator!
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Re: wood burning stoves

Postby woolly1 » Wed May 25, 2011 8:25 pm

GeoffHammond wrote: It has a jacketed flue for heating water. I don't believe a jacketed flue gets as much heat into the water as a wet-back does. I think it also means I have to get an amount of hot exhaust moving up the chimney to heat the water and that sometimes the fire needed to achieve that amount will be more than I need to heat the room.


I too have installed one of these flues on my wood heater and found the same thing. They only work well when the fire is going hard. I am looking to replace it with a loop of steam pipe in the firebox where the temps are the highest, that should work better. I also found the flue chokes up more often and needs to be cleaned every few weeks. I am using a mixture of redgum and whatever wood I can find on my property in Woodend. Not sure on what type of gum they are. :oops:
I also have a rayburn wood stove with a wetback and that does a very good job of heating the water, but not such a good job of heating the house.
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Re: wood burning stoves

Postby Gordon-Loomberah » Wed May 25, 2011 10:58 pm

woolly1 wrote:I also have a rayburn wood stove with a wetback and that does a very good job of heating the water, but not such a good job of heating the house.


Have you considered circulating the hot water from the wetback through some hydronics radiators? It's a good way to distribute the heat around the house, especially if you blow a fan across the radiators.
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Re: wood burning stoves

Postby woolly1 » Wed May 25, 2011 11:25 pm

Gordon-Loomberah wrote:Have you considered circulating the hot water from the wetback through some hydronics radiators? It's a good way to distribute the heat around the house, especially if you blow a fan across the radiators.


Forgot to mention we have that as well. But it goes via the HWS first then the water from the tank is cirulated through panels around the house. Everything is connected to the HWS. The evac tubes, the wet back, the heat exchanger in the flue of the inbuilt in the lounge, and the hydronic panels. When we fire up the wood stove it will warm the house, but it does use more wood and is harder for us to keep going than the heater in the main room where we can shut the fire down and still keep cosy.
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Re: wood burning stoves

Postby tonymtber » Tue Jun 07, 2011 5:22 pm

Hi guys...interesting reading here.

I'm in a similar situation....we built a house some 4 years ago & installed a solar HWS on the roof & also had it plumbed into a flu wet-back. The solar is great in summer, but with heating the water only through the combustion heat is just not enough.

I find that the water temp exiting the flu is very hot (to hot to put my hand on the pipe), but I think my problem is the water tank is mounted on the roof some 10+ metres away, so the hot water has a long way to travel.

Does anyone have an idea of how fast the water would circulate with a thermo/wetback system? Obviously there are a lot of variables.

My initial thought of a way of improving this was to fit a new second water tank in the ceiling just above the combustion heater & effectively have 2 hot water tanks. One would be solar only for summer use & the other used in winter only heated only off the combustion heater. I would isolate either heater depending on the time of the year.

I'm hoping if the new tank is directly above the combustion heater & a large pipe is used, then the water would circulate much quicker, heating the water much more effectively.

Any thoughts or suggestions?
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Re: wood burning stoves

Postby bradley.jarvis » Tue Jun 07, 2011 5:31 pm

Insulate the pipes too and from the HWS to the flue jacket(not a wetback as a wetback is a water box at the back of the fire box)

I have used sheep wool wrapped around the copper pipe and held on with duct tape. Make sure the copper pipe is big too, ours is 3/4" OD to and from the wetback(it is at the back of the firebox)
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Re: wood burning stoves

Postby Gordon-Loomberah » Tue Jun 07, 2011 5:39 pm

The Everhot wet backs use 1" copper pipe for the thermosyphon, and I use 3/4" for the thermosyphon on my 108 evacuated tube hydronics water heater, which works well.
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Re: wood burning stoves

Postby tonymtber » Tue Jun 07, 2011 6:27 pm

Yes, the pipe is insulated all the way back to the tank in black foam (the normal stuff used in plumbing). The pipe is 3/4.
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