sawdust burning stove

A quick warning..................make very sure you know what type of saw dust you are burning. Use only natural wood shavings. Treated lumber has Copper Sulphate amongst other chemicals infused into the wood and when burned gives off toxins!! Also, treated timber from just a few years ago contained Arsenic which also is highly toxic when burned, so please make sure yo know what you are puttin in that burner.

how would you fit a chimney for the smoke to the greenhouse?

thats the word i was looking for, flue.  

cool, im thinking of getting a paraffin heater...

I have just given one of these away.
I bought it for my workshop rather than the greenhouse but I can give you my thoughts on it.
 Firstly, its easy to light,  and when burning well leaves only a small amount of fine ash, . Leave about 2" of ash at the bottom at all times, it burns better for it.
I produce lots of shavings, chipping, and actual sawdust with my joinery business, as well as offcuts Hard and softwood, and the occasional bag of Ash Birch etc logs was bought in for the stove as well
These all burn differently. and require different settings of the dampers to control the burn rate.

These stoves are top loaders,  with 2 air inlets, both controlled by flaps set on the top of the stove. One introduces cool air, straight to the top of the fire and the other draws the air down a cast iron tube to near the bottom of the burning chamber. The air drawn down the iron pipe when the fire is lit  becomes superheated and helps create a very intense burn at the bottom of the stove.
So how is it lit, controlled and cleaned?
I usually lit it by the time honoured method of newspaper, fine kindling, or stiffer card, then gradually feed in heavier pieces. Never try and start it with just sawdust or shavings,  it will not generate enough heat to self sustain.
When the first layers of paper and kindling are lit, close the lid and open the cold air inlet... This will cause the fuel to soon burn very hot and quick, so be ready with larger pieces of wood, or small logs, make sure these have started to burn then half close the fresh air inlet flap..Keep adding  heavier logs gradually untill the chamber is about 1/3rd full of glowing logs/embers.
Now it is ready for sawdust...Fill it up to half to 3/4 with sawdust and leave both flaps half open............The heat will depend on the species of timber you are using, hardwood is not as hot as softwood but burns more slowly, all sawdust burns about the same rate, hardwood slightly longer but I doubt you will have the luxury of hardwood sawdust.....
Keep a note of the settings, the heat output, and the damper settings. Experiment.... but with luck, and starting  the fire as above, by this stage you can fill the chamber up as far as the flue outlet. ( Do not cover the flue outlet. fire will begin to go out straight away ) and with the flaps closed down to a 1/4" opening  the fire will stay in a good 10  to 12 hours giving a steady heat  throughout. If the flaps are open more. it will be hotter and not last as long.
If you get to know how to do this succesfully, and regularly, it is possible to catch the last six inch of glowing embers, top up with sawdust to maximum again and keep the stove going this way almost indefinitely.
The smallest stove in this range gives out about 4 kw max, and thats on a fierce burn which wont last long, so I would reckon on a longer slower burn you would get about 1 KW, one bar electric fire. Ample for keeping air above freezing, depending on the size of the greenhouse.

All the above is of course dependent on correct assembly and very importantly, having the correct flue and pipe work.
I used a flue of about 3.5 mtrs  with the correct (and expensive) insulated flue section going through the roof( ordinary single pipe will get chilled outside and cool the smoke inside, which will then not rise and slow or stop the combustion, maybe even give blowback )
The Ash, if the stove is burning well, is minimal and very fine, almost white whatever you burn, and is OK for the soil if mixed in well when dry, do not add in shovelfulls, and never when wet. Always use the ash bone dry so it mixes easily. Wet ash is as good for soil as cement.  sprinkle it in and mix well with the soil. Also as a dusting on the compost is OK.
Saying that when its burning well there is hardly any ash, and remember it goes better with about 2 " left in the bottom.
Try and keep as much flue as possible inside the room/greenhouse because this gives out a lot of heat. The better quality IE: thicker, the flue pipe the better radiator it is....

Get some tongs, a long poker and some welders gloves. These will all be useful and never ever start a fire or help a fire along with anything but paper,  no firelighters, turps, meths etc etc. Paper will get it going  from any stage, so just be patient and learn how the flaps affect how it burns.
The flue pipe for mine cost nearly 4 times the price of the stove, but its best not to skimp on this if the stove is a serious investment.

Spuds in bacofoil placed in the hottest embers for an hour or so are delicious, especially when burning apple or plum wood.

and  enamelled mugs placed on top keep tea nice and hot.

Thanks for the information Stree, it was better than the instruction book !! We installed the stove on Saturday and all seems well, looking forward to sowing seeds in a warm, cosy greenhouse