Drying Cabinet

[Scrums]

I'm about to build a drying cabinet in the workshop on the lines of that shown below:

I've read up as much as I can find on the web, everybody's pretty vague on it though.

Bottom left of the cabinet is an air 'intake' vent and on the Rt hand door is an 'extract' vent. The whole thing is heated by 2 x 300w tube heaters in the base, with a dehumidifier (...that box at the top) dragging the air in and pushing it out. The dehumidifier is permanently drained to a sink.

Construction is going to be 1/2" chipboard sandwiching Rockwool insulation.

The shelves aren't going to be solid. but slatted to aid circulation.

Anyone got any first hand experience of these/ think it's a non-starter or see any obvious design flaws?

.....and if I can figure it out the heaters will be thermostatically controlled.

Chris.

 

[Blister]

Chris

Where are you getting the moisture free air to draw into the dryer ?

or are you pulling in the air in the workshop ?

Allen

 

[Richard K]

I built a drying cabinet some years ago - for fudge not wood but I'm sure the principle is the same - and found after some use that heating was not necessary and neither was ventilation.
The dehumidifier supplied all the heating and air circulation as long as both its inlet and exhaust were in the cabinet. All the moisture extracted from the wood then came out of the drain.
This makes the whole thing easier and cheaper to both make and run.
Hope this helps

Richard K

 

[Scrums]

Hmmmm......starting to get complicated....

....the air is 'workshop air' (unless I can find some especially dry stuff for sale cheap on ebay - I don't know what else I could use ?

no heaters eh ? the tube ones aren't all that expensive - obviously there's the cost of running them - but I find dehumidifiers don't do very much below about 15 degrees (...apart from frost up, that is)

Chris.

 

[dickm]

I'm probably misreading your post, Chris, but as shown, it looks as if all the dehumidifier is doing is drying the <exhaust> air, and sending drier air into the workshop. Or are you using it to dry the incoming air, so that drier air passes over the timber?
My worry would be that if it works well at drying the air, it will also dry the timber out too fast, especially with heaters added.
Are there details of the Arrowsmith kilns anywhere on the web? Might be possible to get design ideas from that.
There was also a design for a kiln in Practical Woodworking (I think) back in the 1980s. I've got the mag somewhere.........
If I find it, could .pdf it to you?

 

[Richard K]

Agreed about the dehumidifiers not doing much below about 15 degrees but if the dehumidifier is in the cabinet and so are both its air inlet and outlet vents then there is a net heating effect from the machine itself as there are losses due to its inherent inefficiency and these appear as heat which stays in the cabinet.
The two coils - heating and cooling will then be in the cabinet and there will be more heating from the hot coil than there will be cooling from the cold coil - think of it as a fridge with the door open.
The temperature of the cabinet will then depend on the heat balance between the excess heat from the dehum. and the losses through the walls. In practice it will probably settle at about 30 degrees. This may be too hot and dry the wood too quickly so some cool air may be necessary but trial and error will be needed to get the temperature right.
I would be interersted in the result.
Good luck!

Richard

 

[Scrums]

....great ! - I'm getting some good input here.

as you can see I haven't the slightest idea what will happen, the idea as I see (saw) it was to drag workshop air through the wood stacked inside and heat it and the wood, using the dehumidifier to take moisture out of that air and push that out of the top vent, therefore drawing some more air in to the cabinet for the process to continue.

If I can rig up a thermostat to control the heating, I can monitor the whole thing and shut the heat down as required.

dickm: if you can dig out anything I'd be very pleased to see it.

 

[jpt]

HI

The best ones I have seen working are a simple cupboard, as in your picture, with one inlet on the bottom left hand side and a outlet at the top right hand side.

He had installed an old bathroom extractor fan on the outlet which was run 24 hours a day. He has two of them one in the workshop and a larger one outside. The one in the workshop dries the wood a lot quicker as the air is warmer and drier.

He also has a home built small kiln for drying rough turned wet bowls. This is about 3' square and 2' deep this just has a vent at the bottom left hand side and a large vent at the top right hand side. He has a 100watt bulb in the bottom of the box and he reckons he can dry a 12" bowl in under two weeks.

He uses the wire shelves you can get from most DIY stores for wardrobes in all the cupboards.

I keep meaning to build one myself but havent found the space to put it yet.

john

 

[dickm]

While rooting through my vastly too big collection of woodworking books, I found:-
"Fine woodworking on Wood and how to dry it", dated 1986, ISBN 0-918804-54-X.
Like all the FWW books, it's just a compilation of articles from FWW, but it contains a design for a dehumidifier kiln (plus several others) and also a "make it yourself" moisture meter with all the calibration data. Could be useful to anyone interested in doing their own kilning. Dunno if Stobarts still have it in their catalogue, but a library might be able to get hold of it.

 

[CHJ]

Looks like there are still copies around

 

[Scrums]

Change out of a fiver too !!

 

[dickm]

I suspect mine was probably 50p from a charity shop .

 

[wasbit]

I've been desperately searching through my old magazines for an article that I'd seen on making a drying cabinet. No luck so far but from memory ......

The author used an old fridge because of the insulated cabinet and adjustable shelves. It included a thermometer and hygrometer a single light bulb as the heat source and may have had a small fan to keep the air flowing.

If I come across the article I'll post the details.

 

[RATWOOD]

Hi Chris
if the wood is not to big a Microwave will work

 

[Scrums]

Thanks wasbit & Ratwood......I'm trying to dry a bigger quantity of wood than that. As for microwaving, yes I have one in the workshop and it does work on pen blanks for instance, but giving small blasts and then waiting for them to cool, then repeating is a very slow process.

The cabinet is now completed, It's about 5' wide, 8' tall and a couple of feet in depth - just got to make some doors, complete the electrics and cut some wood to put in it.

I'll post some photos and links when it's there.

Chris.

 

[Paul.J]

Seems a good project Chris,but i haven't got the room for a cabinet so will just have to make do with natural drying and green turning
Will look forward to seeing the finished item.Hope it works.
Paul.J.

 

[slemishwoodcrafts]

Did we ever get to see the finished cabinet? (I know I am 9 years late to this post but still curious)

 

[woodfarmer]

I am in the throes of a similar project, making a heated cabinet for brewing beer

 

[Robbo3]

Presumably a drying cabinet works on the same principle as a wood kiln but is for equalising the moisture content rather than drying wood.

There is a lot of info in a downloadable PDF file here
- http://dnr.wi.gov/topic/ForestBusinesses/kiln.html