Condensation inside a close box

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  • #26
MATLABdude
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If you just hermetically sealed the box, and then put a big can of desiccant inside of it, you'd be able to remove enough moisture from the air to prevent substantial amounts of it from freezing out / condensing on your components.

However, such cases exist, and many have been around for over a decade (I remember when Tomshardware or Anandtech or some such first broke the 1 GHz barrier using just such a case on an original AMD Athlon CPU). Most of which have a way to compensate / eliminate frost. For instance, this unit from OCZ:
http://www.hardwaresecrets.com/article/377 [Broken]

However, how are you so sure that your computer case is, in fact, overheating? It's a whole lot easier (and cheaper) to just add some additional 80 or 120 mm case fans and periodically blow out the dust in your computer / fans. Remember to arrange the fans so that you have air flow, and not have them working against one another:
http://pressf1.pcworld.co.nz/showthread.php?t=47317

EDIT: Welcome to PhysicsForums! However, you should post questions like this, either in a new thread, or in the Computer sub-forum
 
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  • #27
stewartcs
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I have an out-door cabinet (with PCB) that over time is being damaged due to condensation (humidity).
I would like to minimize these damages over time (corrosion, etc...)
The cabinet is closed but not 100% sealed. Cabinet size is 80X20X20cm.

How do I avoid the damages due to condensation of air inside the cabinet?
Changes I can implement are:
1. Changing the external geometry of the cabinet.
What would be the preferable geometry?
2. I can change the coating of the internal components (cabinet included).
Any recommendations?
Install a purge air system that has an air dryer on it. The PCB should have a conformal coating on it as well. These coupled with the proper rated box (IP rating) should solve your problem.

CS
 
  • #28
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So in a simplistic way...lets’ say you have a sealed enclosure from the outside with silica gel inside and some heat generating electronic device inside the enclosure. Would that be enough to prevent condensation inside the enclosure from forming?
 
  • #29
Hi, if your still looking for some help on this, check out www.ddbunlimited.com
They provide sealed weatherproof enclosures that reduce the condensation problem and are also secure against vandals and theft. They offer heat and cooling options. They are reasonably priced as well.
 
  • #30
Where possible use a sealed enclosure - it stops water & dust getting in. You should then consider placing a VENT on the enclosure. A VENT will equalise the pressure inside the enclosure with the outside.
WHY? When you get a change in temperature you get a change in pressure. This difference places strain on the o-rings /seals of the enclosure - potentially damaging them - which could lead to future ingress problems. The VENT allows air to pass through the membrane without letting water or dust in. There are different VENTS with different air permeability & water entry pressure ratings.
The VENT also allows any 'moisture' inside to escape out of the sealed enclosure. We provide VENTS in a number of formats & sizes - depending on the size of the enclosure.
VENTS are used in outdoor wireless enclosures, in a sealed box with a battery inside, they are used on a car headlight - to stop condensation on the glass, on outdoor LED lights.

Additionally - you can consider heating your enclosure. We provide heaters which can stop your electronics/components from freezing and potentially failing. The heaters also prevent condensation. We have very small heater that is 5W - OD 10mm and 45mm long - & then we have larger ones... These connect to a small thermostat which regulates the heater.

We also have DRAINAGE VENTS: these are place in the bottom of an outdoor enclosure, and allows water to drain out through the vent, without letting water dust or bugs inside your enclosure.

So - don't rely on GEL packs, what you should be doing is preventing the condensation, not trying to do something about it once you've created the environment for it to happen...
see: www.selectronix.co.uk
 
  • #31
jim hardy
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"""I am sure there is a mechanical design that I can drain the drops accumulating over time.
I just wonder if there is a thumb rule or know how I can follow.""

I wonder if it's really condensation or rain.

in my low-tech industry there were simple rules:

1. All conduit enter from bottom, never side or top. Holes in the top ALWAYS leak.

2. All conduit have a drip loop just priior to entry. Drip loop is a bend that looks like a sink trap , with a drain hole in the bottom. That lets water that somehow got in the conduit by rain or condensation drip out the low point instead of filling up the box.

3. Use drip-proof boxes, ie they have a lip around trhe lid that diverts water away from the door seal. Small drain hole in the bottom. Make the hole, and the ones in conduit drip loops too, small enough that mud-dauber wasps won't fill them with mud in their breeding season. Or cover it with screen. The Swagelok company (Parker Hannefin) makes brass tube fittings for that purpose, ask for "Mud Dauber Fitting". Also handy as fuel strainers in your boat tank..


4. Mount the board high in the box just in case.

In extreme cases we'd run a trickle of air throough the box from our inhouse compressed air system. But be sure your air source is clean and dry, not at end of a long pipe run. A volume change every hour or so does the job.
 
  • #32
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If the cabinet is sealed, you might consider using an ionic membrane dehumidifier.

It is a solid state device that mounts on the side of the enclosure and reduces the humidity through electrolysis. Not the cheapest solution, but maintenance free, long lasting, silent, and inexpensive to run from a 3V dc source. The website is at www.rosahl.co.uk http://www.rosahl.co.uk
 

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