Plumb Dangerous Thinkin

[Fla._Deadheader]

Eggzacktly, how does a de-humidifier work???

 If ya got an old air conditioner, and it doesn't get cold, will it still take moisture out of the air???  If it will blow warm air, instead of cold, why would it not dry wood, in a tightly closed environment???

[Tom]

I canT talk like a book but here goes........

Warm air holds more water than cold air
Cold air gives up water the colder it gets

A tightly enclosed space has no way of getting rid of the water even if you get it out of the wood.

So, Here's kinda what you do.
Heat the wood and the air so that the air can become saturated with water.

Take the saturated air to another place and cool it.  The cool air will drop the water.

Get rid of the water and send the dry air back in there where the wood is to be warmed back up so it can carry the water out again.  (A DH might work in an enclosed area if you can get rid of the water.)

A stack of wood is hard to get the water out of because it's hard to move the air inside of the stack.  You have to get rid of that water-saturated air from inside of the stack.  That's why you stack wood in fairly narrow stacks in the open or move the air with fans in a kiln.

Now somebody that really knows will come along and give you some formulas

[Fla._Deadheader]

  By tightly closed, I MEANT set the A/C up, as you would a de-humdinger. Ain't they about the same thing??? A de-humdinger don't have cold air, right

[tawilson]

Sounds like your old air conditioner is broke. So no cooling or dehumification. A dehumidifier cools and heats the air to get the moisture out and send it out at the same temp. So a functioning air conditioner could work.

[woodhaven]

Tom,
You did a right good job at that. I would never have gotten that far down to earth.

FD,
Be a little more specific and I will give it a shot.

Here is a couple of things to consider.
Water boils at 212 Degrees
The Refrigerant in a window unit boils at -20 degrees
Technically speaking cold is -460 degrees
There is still heat in the air down to -459 degrees

You are right in the fact that a dehumidifier or air conditioner doesn't have cold air.
It does have air that the heat has been removed from. It may seem the same but there is a big differance.

[Fla._Deadheader]

 I just got back from a visit with Ole Jeeves. He says that there IS a cold coil in a de-humdinger, that condenses the water from the air Guess my idea wasn't so dangerous after all

[woodhaven]

You are zactly right. The cold coil is the evaperator and containes the refrigerant with the -20 degree boiling point.
That is exactly the same coil that is in front of a window unit.
The one that sweats. If you had -20 degree blood in your body you would sweat at a low temp too.

[Fla._Deadheader]

Then, can ya reverse the fan on a A/C and get a BIG de-humdinger

[woodhaven]

Nope
Try again

[Ianab]

Okies...
I'll have a go at explaining how it works
Here's my simple DH unit with the covers taken off  



The components in a DH and an airconditioner are basically similar, but the air flows thru the DH in one path. In an Aircon you have your inside air thru one radiator, and the outside air thru the other one.
Does that make sense  

Ian

[tawilson]

A picture is worth a thousand words.

[woodhaven]

FD,
Got any questions about Ianab's picture? It's perfect. There is one missing component which wouldn't mean much to you at this point.
If you stuck a fan between his two coils and had the air blowing forward out of the cold coil you would have turned it back into a AC unit.

[Fla._Deadheader]

  I think I's got it !!!!!!!!!!!!!!!!

[LeeB]

So if you reverse the fan in an a.c. you get a dehumidifier? LeeB

[woodhaven]

Nope, Not at all.
If you reversed the fan what you would get is little to no air flow.
The fan blade pitch is directional. Changing that would do nothing.

[Don_Lewis]

There is a difference in the pressures of the two coils. In a DH kiln, depending in the refrigerant, the fluid is boiling off at about 40 PSIG. In order to boil anything, water or refrigerant you have to add heat. In a boiler, the heat comes from the fire. In a DH unit, the heat comes from the air. This causes the air to be cooled and when cool enough, the water in the air condenses. Then the refrigerant pressure is raised by the compressor to about 300 PSIG, the condenser does just what a steam coil does, condenses the gas to a liquid giving up heat to the air. The heat given up is the total of the heat removed by the evaporator plus the energy put in at the compressor. You have all had the experience of using a spray can and haing it get cold as you spray. That is the refrigerant boiling off just like in an evaporator. If that refrigerant could be collected at the spray nozzle, and pumped up and put back in the can, you would have a refrigeration system and the sweating on the side of the can would be dehumdification.

[woodhaven]

Don is also right.
If you could take a glass of refrigerant and pour it out it would disapear before it ever hit the floor. Back before ozone became such a big issure I could do all kinds of things with refrigerant. Not anymore nowdays you can go to jail for stuff I did. Anytime I had a part that needed to be shrinked to fit I just spray some Freon on it. A lot quicked than leaving it in the freezer overnight. If any of you have ever changed piston sleeves in a engine you know what I mean.

[rs1626]

so if you unhook the fan in the a/c unit and connect a fan to
the front of the unit will it work to dry lumber?

[Buzz-sawyer]

simple question ;
simple answer;
put old inefficient ac window unit on a table in the middle of a closed room, and it will both heat, and dehumidify at the same time
answer, YES

[tawilson]

That's if it is still functional. Fla_Deadheader started out by saying he had "an old air conditioner, and it doesn't get cold", so I took that to mean it was broke, so no cooling or dehumidifying.

[woodhaven]

Thats right,
I would hate to see some of you guys try this and then say we are crazy because it didn't work. You need a good AC not a piece of junk.
The first 40% of what any AC unit does anyway is dehumidify your house then it starts to cool.
When I do a heat loss and heat gain calculation on any structure you would be surprised at the unit size if it were not for moisture removal.

[Buzz-sawyer]

Right Guys...
It can be a 1965 model with no plastic left on it ....but it HAS to be a functional a/c unit....it must dehumidify and heat....that all there is to it
plain ...simple

[Don_Lewis]

It will work as a dryer as long as the system is still functional. There are two main problems. It won't last long because corrosion form the acid in wood will eat up the wet surfaces quickly and it can't function at high enough temperatures to be effective. The airflows are designed for around 70F so when you raise the temperature it becomes less efficient and may not even take water out of the air when you get down to 30% RH, which you need at the end of the cycle to get to 6%. But people do it and you can dry wood that way just not very well.

[Ianab]

But people do it and you can dry wood that way just not very well.

Very true, you aren't going to make a $10,000 DH kiln with a $200 second hand aircon unit. But to dry small quantities of timber, or get your 20% airdried wood down to 10%, it is practical. You wont have killed all possible bugs, you wont have set pitch, it wont be fast.... Just be aware of the limitations and if you can work with them go for it.

[Buzz-sawyer]

I hold a slightly different opinion .....in that I got the a/c unit for free ( and most old r-12 units can be had for $50-$100 or free) and I feel it works exceptionally well,(in light of the cost to to usefullness ratio)
as far as corroding and dissintigrating into pieces ...havent seen that happen.....if it does after 5 or 10 1000 bdft loads SO? visit another garage sale and set another one in there , right, Harold!
and the OLD r-12 units do function fairly efficiently at higher end of cycle (as discussed in previous thread....

    regardless it is satisfying to me personally to collect the parts and make something for free that can turn 1000 feet of air dried into6-8% lumber essentialy for the cost of electricity ($50).....results may vary , but the fun of DOIN it doesnt....
Keep those projecs flowin....good fun guys good input all...
Don

[Fla._Deadheader]

  Geez, Now I wish I actually HAD that A/C unit I started this post about.

 I was just doing some deep thinking and came up with the idea of what the post is about.

 If the A/C unit was placed completely inside a container containing 300 bdft of 12% MC wood, could I expect to get 6%-7% MC wood out, and roughly how long???  I'm ready to experiment.  Would another heat source be needed, and suppose I heated the wood first and then started the A/C unit???  Or should I place just the front (cool air) end inside the container???

 I have a hot customer that wants 6% Cypress for a demo cabinet for his shop. He wants 1000 bdft on a regular basis, IF I can provide the 6% MC.  

 So far, this thread is helping me understand how this drying stuff works.  Thanks, Guys

[woodhaven]

FD,
If you are already down to 12% I don't think I would waste the time to hook up a dehumidification unit(AC). It would take very little heat to go from 12% down to 6%. How come you want to go down so low. 8% is standard for most furniture grade.
If you put the window AC in a container you will want to work out a way to drain the water out.

[Fla._Deadheader]

 This particular cabinet shop wants 6%. I asked the same question and he says he needs 6%???  He has a concrete block storage building and the day we were there, the overhead doors (2), were all the way up. He is also ½ mile from the St. John's River, where it is about 2 miles wide.

 I guess he figures by the time he gets to use the stock, it will be around 8-9%

 Would I need to exhaust the hot air to get the MC down???

[Den Socling]

Why don't you walk into this guys shop with a moisture meter. Meter stuff that looks like it's been around awhile and then tell him you will finish the Cypress to his EMC.  

[Fla._Deadheader]

We talked about that after we left the shop. However, new customer and LOTS of unsold boards makes discretion the better part of valor

[Larry]

Find a kiln that will dry it for you to 6%.  Cost should be in the range of 150 to 400 per mbf.  If it looks like it is going to work with the cabinet maker than think about buying a kiln.

1,000 bf on a regular basis is a lot more than any of the home built kilns using an AC or DH can produce on a regular basis.

[woodhaven]

Den might have a different thought but I don't think you need to worry much about the water at this point.
If you are already down to 12% you don't have much water left. With it being that low I would throw 150 degrees at it for a day and recheck it.

[Larry]

WH,
Your right not much water left but it’s the hardest water to get out and requires a lot of time or heat or something.

[woodhaven]

Delivery it on a rainey day. Tell him it was 6% when you left home.

[Fla._Deadheader]

That's a concern that has me wondering. Ya know, we start the rainy season in May, and we have to go 170 miles, and try to keep this stuff at 6%

 Been thinkin about getting a storage bay up near the camp, and put a de-humdinger and small heater in there and let 'er dig. Add more heat near the end???

[woodhaven]

You must be making good money. That seems like a lot of extra work.

[Fla._Deadheader]

Just trying to figger out a way to get dry lumber, without spending a LOT of bucks.

 IF we sell out and move, I will put in a Vac Kiln, like Den proposed in an earlier thread.