Port-Side Office Trips: Isolator Corroded by Salt Air

An isolator tripping intermittently at premises close to open water, with the enclosure intact and correctly sealed. No water is found inside at any point. The frequency has increased gradually over a period.

An intact, dry enclosure that keeps tripping rules out the two explanations most people reach for, which leaves whatever arrives without any water. An outdoor box heats through the day and cools at night, drawing air in and pushing it out with each cycle. Near open water that air carries salt, which settles on every surface inside and keeps moisture against the metal. Opening the enclosure and looking at the terminal faces settles it directly.

Enclosures are sealed against rain rather than against air, and daily heating and cooling makes them breathe. Near the coast the air drawn in carries salt, which is deposited on every internal surface and never leaves again. Salt keeps moisture against metal, so terminals corrode inside a box that has never seen a single drop of rain. The seal is doing exactly what it was designed to do throughout.

The terminals are cleaned and protected, and the enclosure is put on a short inspection interval appropriate to the location. There is no seal that prevents this, so the answer is inspection and protection rather than a better box. On any coastal or port-side installation, the inside of an outdoor enclosure is worth looking at much more often than an inland site would need.