Wood-fired boiler heating questions

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Wood-fired boiler heating questions

Postby RosieB » Thu Jul 18, 2013 8:39 pm

[Moderator - split from someone else's introduction thread]

We are in Southern Tasmania so it is pretty cool for 3/4 of the year. We are considering installing a Klover wood boiler fireplace which will heat the room and also run under floor heating and radiators via a wetback. It is an Italian product but we can't find any information about how it performs. It is similar to the Sophel but we are told it will burn around 8 hours where the Sophel is only 5 hours. Burn time is critical. We don't want it going out over night or during the day when we re work. Has anyone any experience with this heater or the Sophel? We are in a valley so solar is probably not an option.
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Re: Wood-fired boiler heating questions

Postby davidg » Fri Jul 19, 2013 12:41 pm

RosieB wrote:We are considering installing a Klover wood boiler fireplace

Is that one of the pellet system units ?
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Re: Wood-fired boiler heating questions

Postby TsaTsa2CV » Fri Jul 19, 2013 5:43 pm

Hi RosieB,

I have no idea how long the burn rate is, as our Sophel had not been fired up yet in our new off grid solar house.It is hooked up to a 400lt header tank directly above the fireplace and to hydronic slab heating. The 400lt header tank also incorporates a 45m copper coil preheating hot water to the heat pump hotwater system for winter operation. It incorporates a 2.4kW electric boost/load dump element. We have 5.55kW of panels facing north and have excess power for 3/4 of the year which is why we use this excess to heat water during the hottest part of the day.
Our house, in a rather cold are in Buxton Vic, is very well insulated, double glazed smart glass and argon gass filled and getting full solar penetration in winter (when the sun shines.....) and full shade in summer.
We do not intend to have the Sophel burn 24/7 and hope to have shorter but hot fires creating less smoke and pollution. The Sophel boiler is rated at max 30kW which I guess is best case and dependent of quality of wood burned. Time will tell how it will perform with our own timber. More than enough on the ground on our 95 acres to see us out. When everything is operational I will post the performance of the house, heating and hotwater systems.
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Re: Wood-fired boiler heating questions

Postby RosieB » Fri Jul 19, 2013 8:25 pm

Thanks TsaTsa2CV, I will be interested in your report. I can't believe you have not fired it up yet!
Davidg, we are looking at a wood fired hydronic fireplace heater as pellet supply is not assured. We are looking at an installed Farmar tomorrow out of interest. Similar concept to the Sophel and Klover. Will post a report on that as it might be of interest to other readers.
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Re: Wood-fired boiler heating questions

Postby davidg » Fri Jul 19, 2013 9:01 pm

While I have not started started building our house on the farm in central Vic, one thing I have spent considerable time on, is heating for the winter, using hydronic and in slab heat design the other part is the fire and heat storage for the nights, my design has 2000litres of water above fire in my tanks heated to a high temp, this will provide the extra top up of heat overnight, boosted by solar during the day, boosted by ground source heating stored from the summer, not to mention the slab itself.

So you ask whats my point. A suggestion ramp up the size of the water storage with good insulation to keep it hot to compensate for overnight heating rather than trying to run a fire overnight that's all a relatively minor cost big increase in benefit. :mrgreen:
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Re: Wood-fired boiler heating questions

Postby Cherokee Solar » Sat Jul 20, 2013 11:15 am

Hi RosieB,

I'm up in the mountains in central Vic. It snowed this morning. We run an Australian made Metal Dynamics "Gourmet Cooker" wood stoven / oven with an 8kW wet back (it can run a 15kW wet back if required).

http://www.metaldynamics.com.au/gourmetcooker.htm

The wet back is enough to run 4 hydronic radiators + hot water system + plus I cook with it every day. The house is small (175m2) but very well insulated (at least twice and then some of a normal house). Without running the radiators the unit can get the house to 22 degrees - which is too hot for me.

A couple of solar hot water panels keep the hot water system toasty during summer.

It will run overnight but will be down to only a few hot coals by morning.

The main issue with wood heaters is burning well seasoned wood. This means cut and stored for at least 24 months to remove the sugars from the wood. The rain doesn't affect this drying process that I've noticed so you can leave them stored in piles about the place so that the air can get into the wood. Just keep them off the ground using plastic or steel because the fungi will get into them and start turning the wood back into soil. However, it is probably worthwhile bringing them in out of the rain for a couple of weeks before you want to burn them. The smaller you cut and split the wood, the quicker it will season and dry too.

With a really big combustion chamber, you'll burn lots and lots of wood which is a real problem. With a really small combustion chamber it'll never heat the house. You have to find a balance between how much fuel you want to chuck in it and how much time you want to muck around with the unit. As a general observation, I reckon people over estimate their heating requirements.

Chris
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Re: Wood-fired boiler heating questions

Postby Smurf1976 » Sat Jul 20, 2013 8:06 pm

Cherokee Solar wrote:The main issue with wood heaters is burning well seasoned wood. This means cut and stored for at least 24 months to remove the sugars from the wood. The rain doesn't affect this drying process that I've noticed so you can leave them stored in piles about the place so that the air can get into the wood. Just keep them off the ground using plastic or steel because the fungi will get into them and start turning the wood back into soil. However, it is probably worthwhile bringing them in out of the rain for a couple of weeks before you want to burn them. The smaller you cut and split the wood, the quicker it will season and dry too.

...As a general observation, I reckon people over estimate their heating requirements.

Agreed there. Wood will season perfectly well just sitting out in the open. It's not rainwater getting in that is the problem, but the moisture trapped within the wood due to it's chemical structure and that only comes out slowly.

As for the size of the unit, an over-sized wood heater (of any type) is a definite bad idea. Combustion efficiency falls in a heap, and pollution rates soar, when they aren't burning at a decent rate. That said, constantly running it flat out will burn it out rather quickly too. So you need the right size, not under or over size.
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Re: Wood-fired boiler heating questions

Postby Cherokee Solar » Sat Jul 20, 2013 8:58 pm

Hey smurf,

Too true.

The sales people love to sell you the biggest unit that you ask for. It just may not be appropriate for your situation. I have two large panel hydronic radiators in the house, which were a "must have", which have not been required to operate on any single occasion within the past 3 years.

I hope you are getting some good rain down south? The past two months here have brought 250mm! :D Full water tanks. woo hoo!

Chris
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Re: Wood-fired boiler heating questions

Postby davidg » Sat Jul 20, 2013 10:16 pm

Cherokee Solar wrote:I hope you are getting some good rain down south? The past two months here have brought 250mm! :D Full water tanks. woo hoo!

Got some in the last couple of days I was getting kind of concerned about ours, they were getting kind of low, got about 7000 litres in the last day or so, will keep us in water for a couple of weeks, so I don't windup having to use town water, I dislike it and have not had to use it in over two years now.
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Re: Wood-fired boiler heating questions

Postby franks » Sun Jul 21, 2013 6:14 pm

Our 54 m^2 granny flat shed conversion..we are using small cast iron wood heater aprox size 500x400x300mm using 4.5inch flue pipe. does a great job.
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