What factory and workshop air does to an aircon unit

Abrasive dust does two separate things to a coil. It blocks the gaps between the fins, which a wash reverses completely. It also wears and bends the fin itself as air drives grit across it, which a wash cannot reverse at all.

Early in a unit's life the first effect dominates, so every clean restores performance and the result feels like new. Later the second effect takes over. The coil comes back cleaner each time and performs a little worse, because there is less intact fin to clean.

That is why the useful signal on an industrial site is not how dirty the coil looks. It is how long each clean holds. A wash that used to carry the unit through a year and now carries it through a season is telling you the fin is going, not that the cleaning was poor.

Sites differ more than the word industrial suggests. The particle changes which component goes first.

Industrial coils get washed harder because they look worse. Fin material is thin, and pressure that would be reasonable on a household unit flattens it. Flattened fins pack closer together, and the surface area available to shed heat drops permanently.

One workshop unit came in barely cooling with a coil that had already been cleaned. The fins had been flattened across several sections by an earlier pressure wash, so the cleaning had made the airflow problem worse rather than better.

Ask what pressure is being used on the coil, and ask for fin condition to be reported after the clean rather than just the fact that it was cleaned. On a site where washes are frequent, the cumulative handling matters as much as the dust.

Two industrial failure paths get misread as dirt because everything on site is dirty. Neither is.

Vibration from neighbouring machinery travels through shared ground and structure. Over months it crumbles the levelling blocks and works mounting bolts loose, and the unit starts to rattle. Nothing in the aircon has failed; the thing holding it still has.

Sustained heat is the other. A frame in direct sun for most of a working day runs far above ambient, and rubber mounting isolators perish faster under that. The result is vibration transmitted straight into the structure, which reads as a failing compressor from inside the office.

Interval should follow running hours and what the air carries, not the calendar. A unit beside active workshop activity loads its return filter far faster than an interval set for an office ever accounts for.

The checks worth adding: fin condition reported not just coil cleaned, the blower wheel inspected on both sides rather than assumed even, the isolator opened and the cable entry checked for corrosion, and mounting hardware torque checked if there is machinery nearby.

The point at which to stop cleaning and price a replacement is when each wash buys visibly less time than the one before. That is a measurable trend, and it is a better basis for the decision than the age of the unit.