Condensation inside a close box

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    Box Condensation
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Discussion Overview

The discussion centers around strategies to minimize condensation and its damaging effects on an outdoor cabinet housing a PCB. Participants explore various approaches, including changes to geometry, coatings, and environmental controls, while considering practical limitations and costs.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant suggests changing the cabinet's external geometry to mitigate condensation, while others argue that geometry changes may not be effective.
  • Some propose using specific coatings for PCBs and components to protect against moisture.
  • A participant mentions the use of desiccants like silica gel, but expresses concerns about the practicality of regular maintenance.
  • There are suggestions for weather sealing the cabinet using gaskets and sealants to reduce moisture ingress.
  • One participant raises the idea of using a heater to maintain a temperature above ambient levels to prevent condensation, while others question the feasibility and potential for heat damage to components.
  • Another participant discusses the possibility of designing channels to direct condensed water away from sensitive components.
  • There is mention of using heat tape as a potential solution, although concerns about electrical control and implementation are noted.
  • Some participants highlight that outdoor electrical cabinets often use protective coatings and may incorporate design features to manage humidity.
  • One participant notes that telecommunications companies use foam to fill junction boxes, which may complicate maintenance but could reduce air volume and moisture issues.

Areas of Agreement / Disagreement

Participants express a range of opinions on effective solutions, with no consensus on a single approach. There are competing views on the effectiveness of geometry changes, the practicality of desiccants, and the use of heating elements.

Contextual Notes

Participants acknowledge limitations related to the cabinet's sealing capabilities and the challenges of maintaining a controlled atmosphere. The discussion reflects a variety of assumptions about the effectiveness of proposed solutions in real-world applications.

  • #31
"""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 let's 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.
 
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  • #32
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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