Enclosure Condensation
Condensation is the moisture carried by the air inside an enclosure turning into water droplets on surfaces as it cools. It occurs even in a sealed enclosure, because sealing traps moisture inside just as much as it keeps it out. It is a common cause of corrosion, leakage current and intermittent faults on circuit boards.
An enclosure that warms up in the morning sun and cools down at night goes through a pressure cycle every day. With each cycle some humid air gets in through gaps in the seals and condenses as it cools. The condensed water cannot get out; it collects at the bottom of the enclosure.
- Symptom: white-green salt deposits under the board and oxide traces on connector pins while the enclosure seems dry inside.
- Effect: the damp surface forms a high-resistance leakage path between neighbouring conductors, causing false readings in signal-level circuits.
- Solution: a breathable vent plug or cable gland with an ePTFE membrane, cable entries facing downwards, and approaching the enclosure with a ventilation mindset rather than fillers/desiccants.
In an enclosure with condensation problems, the first thing to do is not to look for leaks; sealing the enclosure tighter makes the problem worse. Apply a pressure-equalisation solution, give the cable a drip loop before the entry, and avoid mounting the enclosure on a surface in direct sunlight.
Context where this term is used: Installation, Redundancy and Field Continuity