Air conditioner and humidity (Full Version)

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Guest -> Air conditioner and humidity (May 20 2005 16:28:41)

Hi friends.

How much does air condition dry out an already dry workshop?

I know about nothing about this theme, and the info I've been given is not very clear.

My workshop in southern Spain is very warm in summer, and I have to humidify and/or keep the windows closed in order to keep the relative humidity above 40%. I was thinking about installing a cheap air condition system, but have been told that it might dry out the workshop to much. Other people have told me that if it's not turned on all the day, it wont be a problem, and that the fact that the air is cooler will make the humidity higher, or more or less stay on the same level.

So what to believe.

Thanks
Anders



Escribano -> RE: Air conditioner and humidity (May 20 2005 18:15:23)

I've seen humidifier/dehumidifiers - they have to run all the time at a selectable humidity e.g. 50% - Google for "humidifier dehumidifier"



gshaviv -> RE: Air conditioner and humidity (May 20 2005 22:20:04)

quote:

How much does air condition dry out an already dry workshop?


Not a lot. Air conditioners tend to lose their effectiveness in dry climate. So an air conditioner that operates at a 70% relative humidity environment can bring down the RH to 50%. But if it operates at 40% it will hardly have an effect.

Any way, I thought being a bit on the dry side is better then being a bit on the humid side. My understanding is that if you put a guitar in drier climate then it was built it may crack, while is you put is in a more humid climate it will just sound bad, and may buzz, but that is reversable (while a crack isn't).



Thomas Whiteley -> RE: Air conditioner and humidity (May 20 2005 23:18:12)

Anders;

There are different technologies used to cool air indoors. Swamp Coolers, Evaporative Coolers, Air Conditioners and Heat Pumps are amongst the examples to look into.

There is a bit more to the subject then I present here. This is one of the topics we studied in Engineering College years ago. So my information might be out of date! [:)]

Swamp Coolers loose a great deal of efficiency at humidity’s over 50% or so. I speak from personal experience!

Air Conditioners will remove excess moisture from the environment thus lowering your humidity. A low fan speed should be used on humid days and a high speed when humidity is low.

There are other issues besides the type to use. Be sure you calculate the cubic area of your environment in regards to the unit you purchase. Also be sure there will be no health problems from the filters used.

You can purchase a unit that will control your humidity or add a humidifier if necessary.



Guest -> RE: Air conditioner and humidity (May 21 2005 6:35:05)

Thanks for your answers.[:)]

The "problem" is that this is Spain and some of the machines mentioned do not exist.

What I'm considering is to buy is a standard and cheap aircondition system to cool down my workshop.
The problem is that my workshop is very dry in summer. I have to humidify in order to keep the RH above 40%.
My worries are that the aircondition will dry out the workshop to much. I have to worry about the guitars I build, but also about the expensive wood which is drying in my workshop.[;)]



Escribano -> RE: Air conditioner and humidity (May 21 2005 8:08:56)

quote:

The "problem" is that this is Spain and some of the machines mentioned do not exist.


I'll see if I can get one in the UK and ship it down with my household stuff. I'll buy 2 if they're reasonable as I may need one as well. I'll have a look around.

BTW - see how the Google Ads change top and bottom when viewing this entire thread with Flat Style?



Guest -> RE: Air conditioner and humidity (May 22 2005 7:52:25)

Thanks Simon

I dont think it's a good idea though. I believe that down here they know more about cooloing than in cold England. Beside, prices are low. You can get split wall units from 180 euros the whole system. So I think it's better for you to see the market, and also test your house before taking descissions. I think you'll be quite fine downstairs, and your big open topfloor will make the house a lot cooler. My house is extremely hot.

I think I'll buy a unit very soon. From what I have understood after having asked on different forums, the drying effect is not very high, if it exists at all when the air is already very dry. So I believe that with a good humidifier, I can make it work so that I can work.



Escribano -> RE: Air conditioner and humidity (May 22 2005 9:23:46)

quote:

I dont think it's a good idea though. I believe that down here they know more about cooloing than in cold England. Beside, prices are low. You can get split wall units from 180 euros the whole system


I meant dehumidifiers - purpose-built



gshaviv -> RE: Air conditioner and humidity (May 22 2005 16:56:48)

Ok, so a little thermodynamics. (Warning: this may be long and not for the faint of heart).

All electric air conditioners I know and have seen selling in the market work on the same principle.

The unit takes freon gas and compresses it, adiabatically. This raises the temprature of the gas. The gas is then cooled off to the outside temperature by running it through a coil and blowing air at it (like a car radiator).

The unit then lets the compressed freon gas which is in outside temperature and lets it drop in pressure. This cools the gas. It then passed the room air through coils running the cold gas, cooling of the air and blowing it into the room.

So what happens with the humidity?

Air holds a certain amount of water vapor. The capacity of air to hold water increases with its temperature, the relative humidity (RH) is the amount of water vapor in the air devided by its maximum capacity.

So air at 40C and RH of 50% actually hold more water vapor then air at 20C and 50% RH.

When an air conditioner cools the outside air, the RH of the air being cooled increases until it gets to 100% meaning the air is cooled sufficiently so it can't hold any more water. The extra water vapor condenses and becomes liquid. This is the water drips you see when an air conditioner operates.

You also see this in the morning, when the air temprature cools down and dew forms on your car. The dew is the extra moisture the air could not hold having being cooled down.

Back to the air conditioner, the air condition blows this very cold air which holds very little water into the room where it mixes with the room. Since the air from the a/c has a very small amount of water vapor (albeit at 100%RH) when it mixes with the room air, it rises in temprature and lowers the room's RH. Which is why an a/c dries the room air.

You can see from this that if the room is at 70% RH (which means it holds a certain amount of water) and you mix it with air from the A/C (which holds very little water) you will not have the same effect as when you mix the same amount of A/C air with room air which is at 40% to begin with (meanins it has less water in it).

In any case if you want to restore the humidity you can use a humidifier, as you've suggested.

As for efficiency, if the outside air is very humid, the a/c will cause more water to condensate. You have to invest energy in turning water from vapor to liquid, which means the a/c will have to work harder.



Guest -> RE: Air conditioner and humidity (May 23 2005 15:00:03)

Thanks a lot Guy.

I think the little grey ones are beginning to understand. I have the feeling that a moderate use of air conditioning and a good quality humidifier could be my solution. You are also right in saying that it's better to be on the dry side, and I find that a dehumidifier is one of the most important investments in a guitar workshop.

My problem is that in 4 - 5 month of the year, it is very hot and very dry, meaning that I cannot open the windows, because the RH drops very fast, and my workshop is about 26 - 30 degrees celcius, which is a bit annoying to work in. Before I just worked less[8D], but since I'm quite busy, thats not realy the solution anymore.

So thanks again.
What would life be without foroflamenco??? the place where you get qualified answers on everything[:D][:D]



gshaviv -> RE: Air conditioner and humidity (May 23 2005 15:49:28)

quote:

my workshop is about 26 - 30 degrees celcius


Sounds like you are humidifying the workshop with your sweat [:)]



Guest -> RE: Air conditioner and humidity (May 24 2005 3:19:39)

Not yet, but during summer...........[:@]



veet -> RE: Air conditioner and humidity (Jun. 1 2005 23:28:34)

In my experience, air conditioners are very good at sucking all the water out of the environment. (That's why, for example, you get very dehydrated on a jet airliner.)
So you'll have to put in some kind of a humidifier to compensate, maybe just a constantly running teakettle..[;)]



Guest -> RE: Air conditioner and humidity (Jun. 2 2005 8:07:19)

Anyone want a cuppa tea? The kettle is on[:D]

Thanks for your reply veet

I've ordered one of these small swamp coolers (portable evaporative air condition[8D]) I like the idea that it is made for a climate like the one here in Granada and that it humidifies instead of dehumidifies.
To be honest I'm very sceptical with this thingie, It sounds to good to be true. I'll let you know.



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