How to build a DIY timber drying kiln

[johnnyboy158]

How About using a fridge trailers heat sorse instead of on the minus setting put it on the plus setting if you can get a working one or is there a moister issue just a though

[Rob D]

What a cracking thread and vid there Big J - spot on!

 

 

I've always used a dehumidifier - but this set up looks better and more controllable...

[broonie]

a wee bit of interesting reading http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr118.pdf

[arbwork]

a we bit 144 pages ! interesting though good thread this 1 good vid, I missed a kiln similar to above on ebay the other month and regret not going a bit higher in my bidding, hope to get there in the end

[Mike Dempsey]

I have a job coming up next monthwhere I will have to build a small dehumidifier kiln. I have to dry a whisky cask out down to about 8 percent so I can make items from it for the whisky distillery. The cask will be soaking wet and if I cut it up into smaller pieces I can get away with building a 1m cubed size kiln. I will sterilize the dehumidifier water collection part as it holds about 5 liters of water except this time it will be collecting pure malt whisky at about £2000 a litre. I reckon I should be able to collect about 2 to 3 litres of whisky easily. The last time I just let the staves dry naturally for about 6 weeks next to the stove and the workshop stank like a distillery for months! My mate who is a copper reckons with the windows in my car down, and only driving for a couple of hours, I must have been over the limit. He is going to give me a breathalyser kit to try out the next time.

[posch jon]

Hi there, Great info on the kiln. What sort of temperatures do you use to dry firewood ?? Thanks Jon

[Big J]

Hi there, Great info on the kiln. What sort of temperatures do you use to dry firewood ?? Thanks Jon

 

I've not got that far as I wasn't able to shoehorn my firewood crates in (made from pallets without the forethought of them going into the kiln) but you won't be able to go much beyond 40 celcius before your electrical kit becomes unreliable.

 

Jonathan

[treedweller]

J what % of the daily cost is down to the heaters and what is down to the fans?? I have a fridge body collecting moss and was thinking about lining it with radiators and having a stove with a back boiler pumping the hot water around. Do you run the fans 24/7?? I was also looking at those solar polytunnel fans but figured multiples of them wouldn't cut it!!??

[Big J]

J what % of the daily cost is down to the heaters and what is down to the fans?? I have a fridge body collecting moss and was thinking about lining it with radiators and having a stove with a back boiler pumping the hot water around. Do you run the fans 24/7?? I was also looking at those solar polytunnel fans but figured multiples of them wouldn't cut it!!??

 

Roughly 830w on the fan (not including the heat recovery, which is around 170w) and I reckon three times that on the heater (2.5kw). Fans are run 24/7.

 

You need to have lots of air circulation, so I'd rather be skimping on heat than the fans. Lower heat simply equals a slower cycle, lower air circulation results in dead spots, mould and uneven moisture contents.

 

Jonathan

[Big J]

Going to try a run with firewood next week. It will be spruce and poplar going in (just what I have in offcuts at the moment). I've built some boxes at that better fill the space than the ones that I previously had, so will be able to get 10.5 cubic metres of firewood in there with plenty of space for air circulation.

 

One thing that I am going to try that I've not done before is a higher temperature but only extracting for 16hrs a day (spread out evenly over 24hrs). The reason for this is that the energy requirement for increasing the temperature in the kiln goes up incrementally in a linear fashion whereas the moisture carried in the air as the temperature goes up goes up exponentially. For instance, 24hr/day extraction at 35c results in 140ltr a day extracted. 16hr/day extraction at 50c results in 265lts a day extracted. All for the same theoretical power draw.

 

Anyway, I've calculated that to take 10.5 cube from fresh to 15% will take 13.5 days at a cost of about £13 a cubic metre in electricity. Sounds like quite a high cost, but I should be able to sell it at at least a £25 a cube premium over normal firewood without it clogging up my yard for a year whilst it air dries.

 

I'll take some photos on Tuesday when it goes in.

 

Jonathan