Thread: My Dehumidification Kiln

I was running a dehumidifier as well, Pete. They work well, but can be expensive if not properly controlled, which was always my biggest problem. If I'd had the time and money I'd have invested in some decent temp and humidity sensors and a proper programmable controller. My timer controller was simply not good enough to be efficient, I'm afraid. still, it made a lot of good timber, so I can't complain too much.

craig,what size was your kiln? i'd like,to down the track set one up in a container and i'm wondering how effiecient they would be compared to a solar kiln

Originally Posted by Exador

I was running a dehumidifier as well, Pete. They work well, but can be expensive if not properly controlled, which was always my biggest problem. If I'd had the time and money I'd have invested in some decent temp and humidity sensors and a proper programmable controller. My timer controller was simply not good enough to be efficient, I'm afraid. still, it made a lot of good timber, so I can't complain too much.

Yes, this is probably a downside of a DH style kiln, the electricity cost, and like you say control is important to keep in check, with my initial setup I left the control switch as is, but normally this switch is setup to control cooling of a room, if the space does not lose heat quickly (and this is not what we want) the rac will just end up running constantly, which in my kiln was plenty to heat the space (easily reached 55°C) but then the evaporator (cold) is not sized to deal with 55°C so ended up not condensing any water, so I pinched a thermostat out of a heater and put this on the condensor (hot) side and this controlled the temp much more effectively, so far 35°C seems to be a good point to aim for, in MK2 kiln I am seeing an on time of ~ 10mins and an off time of ~ 30 to 45 mins, this on off time is a function of the hysteresis of the system as a whole (how quickly the kiln loses heat thru the walls, the thermostat and any air leaks between outside and inside etc) I haven't needed to put a timer on it yet.

I'll see if I can put the kiln on tariff 31 which is 1/3 of normal domestic tariff 11.

Pete

Charlsie, I had 2, each about 30 cu.m total volume, with timber rails running into them contructed out of 8x2s sitting edgewise on 8x3s, the whole lot sitting on the very rough rubber floor of the shed. Drying capacity was about 10-15 cubes of stripped timber in each, with plenty of room for circulation. They were made out of cold room panel, with an internal wall of corrugated iron between the two units.

The 2 units were each 3kW and they really chewed the juice, so I ran them at 10 on, 20 off as much as I could. During summer it was more like 20, 10 though if I wanted to get anywhere.

I'd say solar would be streets ahead efficiency-wise, possibly with some supplementary DH if it's a bit slow.

Just before the year 2000 I looked at building a solar kin. I had seen the Rosegum Timbers setup where they used an insulated 20' shipping container. They placed a sheet of polythene at 45 deg on the roof to form a skillion. The polythene was an Israeli product developed for their market gardens.

This 20' kiln would dry up to 12m3. I didn't have too many customers who would be able to provide that so I planned something around 1 to 2m3. As I have mentioned elsewhere I did not get to build one although I had most of the materials (and still have).

Rosegum's 20 footer used a 1 HP fan to blow hot air from the top collection section down into the container itself. Let's assume the fan only runs during daylight hours and to make the sums easy for my pea brain we will call that 12 hours, this will cost $1.60 at 18c perKWH per day.

150mm x 25mm boards will take around 8 weeks to dry. This will depend on species, time of year, geographical position and whether they were air dryed first (I am in this instance assuming air drying first to about 30%)

So the cost for 10m3 would be $90. Pretty good. So why doesn't everybody do it? This is not fast enough for the large enterprises. They want the hardwood timber out of the kiln inside a week. Softwood they place in the morning and take it out by late afternoon! This is in their high temperature kilns.

But for us, solar is not a bad option. Rosegum timbers are situated at Bellingen, which is pretty close to the coast and quite humid. They have changed direction now and although they still make kilns based on the insulated shipping container (10m3) their products are much more sophisticated than before. Even the little one has solar panels on it.

Just as an aside, when I visited them, my ancient Dyna truck broke down as I was leaving. They helped to repair it so I could get home. A good business story. This is their web site if you are interested.

Solar Dryers Australia - world leading manufacturers of solar and gas kilns for timber drying

Regards
Paul

thanks for the reply craig and paul for the link.