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De-humidifier application

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colinc

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I have finally got fed up with anything I leave out in my workshop picking up rust spots and have bought a dehumidifier.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... :EOAB:UK:6

I hope it's an appropriate size. I have a largish 2 car garage where my lathe, planer, bandsaw & chip collector live (sharing with my 1970 beetle and MX-5) and a single garage sized workshop at the back accessed through the back of the garage. The beetle's going soon as I need the space for a saw - the MX-5 usually only goes out in the dry so it doesn't bring much moisture in.

My question is one of how to utilise the dehumidifier to best effect? Shall I put a door between garage and workshop to try and restrict the airflow and have it just in the workshop or will it be satisfactory to park it somewhere between the two rooms and expect it to do both. There is no ceiling in the garage, just an apex felt and tile roof and the up/over door is pretty gappy at the edges. I have a couple of fan heaters in the workshop and they are ok, but I would like to banish the damp cold feeling I get when opening it up (old age telling).

I know the simple answer is try it and see but I wondered what other people do. Comments appreciated

regards

Colin
 

OLD

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There is no ceiling in the garage, just an apex felt and tile roof and the up/over door is pretty gappy at the edges.
Sounds very well ventilated to me the dehumidifier will be trying to desiccate the world i would close the workspace in to get it working well.
 

colinc

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Yes, I think that I can seal the workshop area off quite effectively and will concentrate on keeping it at a reasonable temeperature and humidity. The rest just seems to exposed to the outside air
 

Argus

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I usually buy seasoned wood, but sometimes I give it a little more gentle drying before I use it. Here are some tips; effectively you are making a kiln and the secret of success is controlling the process.

You don't say what kind of dehum it is, so I'm assuming that it's a mechanical refrigeration type. Dessicant dehums are very fast at removing moisture and not really recommended for drying timber in my opinion.

1. Obtain a reliable air hygrometer and thermometer
2. You will need a hygrostat, if the dehum is not equipped with one.
3. A source of gentle heat to elevate the temperature slightly – the capacity of dehums increase with the ambient temperature. Also the heat of rejection from a dehum is given back into the spade, so keep an eye on temperatures. A couple of light bulbs are sufficient in a small kiln.
4. A hygrostat to control the rate of removal.
5. A good quality moisture meter is highly desirable.

What you don’t want to do:
1. Get the thing too hot.
2. Drag out the moisture too fast – the timber will twist and split. You may get internal shakes that are invisible until you cut it.
3. Be impatient – could take weeks.

So:
Let wet wood acclimatise for a few months first.
Dimension your timber roughly to size in planks
Stack it in sticks
If it is a small quantity, say two or three cubic meter pile when in stick get some thick polythene and make a small tent around the lot with enough space for air circulation and to accommodate the dehum. This can sit in the corner of your space. Even air circulation is crucial.
Proceed SLOWLY
Drying timber is a commercial science. On your scale it is a little hit and miss. Keep a test piece on top of the pile that you can weigh periodically and check the weight / moisture loss.
If you measure the internal humidity, take a several reading and an average, and allow lots of time for the timber to reach equilibrium.
Best of all don’t allow too great a difference in internal humidity and the humidity of the air – it needs to dry SLOWLY and reach equilibrium slowly.

I’ve used a small domestic dehum, (about 2 – 3 L/day), quite successfully for this. Toward the end of the process I tend to increase the temperature and over dry a little as the timber will re-absorb moisture when taken out of the kiln but will find an equilibrium lower than the ambient. Some of my work in Oak is in a centrally heated house for over ten years without any movement.

I think that Fine Woodworking produced a collection of articles on small scale drying and kiln construction many years ago – some good tips in it if you can find a copy.
Does any one know of it?

Good luck
 

The Restorer

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Argus - i remember the article in Finewoodworking.
A few years ago i went on one of Bruce Luckhurst courses on buying and drying wood. Very good and informative. We started at a private plantation in Sussex where a froester talked us through the growing and harvesting and moved from there to a green Oak yard and the onto a full scale commercial yard. All the time being quoted the cubic foot price for English Oak (went from about £5 to £40 in those few steps)
Anyway one of the things that Mr Luckhurst is famous for is that he has built his own Solar Kiln as well as a conditioning kiln and Scandinavian outer timber stores (wooden tunnels with about a foot of soil on top and finished with grass!)
A very good couple of days that included some timber indentification and copious notes to accompany it.
Steve.
 

Argus

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Yes indeed.

I’ve heard about those teach-ins of Bruce Luckhurst.

The article I’m thinking of on solar kilns appeared in the early 80’s, but its still valid now – shall try to find the book it was republished in, now I'm reminded. The author built one in New England, I believe, so it should work in this climate.

Drying your own is tremendously rewarding if you have access to small, commercially unviable quantities. but it can be a very long process and a bit unpredictable.

In my recollection, Holly is the most troublesome……..


Argus
 
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