Each wash bought less time: the coil had reached its end
The factory floor puts more dust through this unit in a week than most homes manage in a year. Cleaning was already on a heavy cycle and still losing ground. When washing stops holding, the honest question is whether the equipment is worth washing.
By Team Snowflake | Reviewed 25 Jul 2026
Case summary
Carrier Cassette15 years oldIndustrialTuas, Singapore
- Concern
- Chemical washing had been running twice a year on this unit, and the expectation was that another round would bring the capacity back again.
- Found
- Fin corrosion and permanent fin collapse across both coils, so each cleaning cycle restores less capacity and the loss is no longer recoverable
- Key check
- Measured supply air right after a full chemical wash and set it beside the same measurement taken after the previous two washes, showing a falling ceiling each time
- Result
- Capacity improved after this wash, then began fading on the same curve as before. Replacement was budgeted for the following quarter. Washing stays on the schedule in the meantime, now understood as holding cost rather than a fix.
What we were told
Output on the production floor had been dropping for two seasons. Chemical cleaning was booked twice a year and each round helped, but less than the previous one. Between washes the airflow faded within weeks. Nothing had failed outright and the unit still ran on demand.
What we checked
This one is answered by comparing washes, not by inspecting a single one. We washed the unit fully, measured supply air straight afterwards, and set that number beside the two previous post-wash readings held on file. The ceiling had dropped each time. That trend told us more than any single inspection could, so the next step was to look at why the metal was not recovering.
Post-wash supply air was warmer than after the previous wash, and warmer again than the one before that.
Fin edges on the outdoor coil were flaking and pitted, with whole bands of fin bent flat and no longer passing air.
Aluminium had thinned enough in places that cleaning pressure risked opening the fin pack further.
What we found
Abrasive dust does two things over a long service life. It blocks the fin gaps, which cleaning reverses, and it wears and bends the fin itself, which cleaning cannot. After enough cycles the second effect dominates. Each wash still lifts the loose material, so the unit improves, but it starts from a lower ceiling because more fin surface has gone for good. The pattern of shrinking gains is the equipment telling you where it is in its life.
What fixed it
We were straight about what more washing would buy, which is a smaller lift each time on a shortening cycle. We put the annual cleaning spend beside the cost of a replacement unit sized for this floor, and included the output lost while capacity sits below spec. On that arithmetic the changeover pays back inside a few seasons. We advised planning a replacement and keeping the wash cycle running until the new unit is in.
Outcome
Capacity improved after this wash, then began fading on the same curve as before. Replacement was budgeted for the following quarter. Washing stays on the schedule in the meantime, now understood as holding cost rather than a fix.
What this case teaches us
Cleaning restores dirt losses, never metal losses
- Washing removes what sits on the fins, and it cannot straighten fins that have already collapsed.
- Track what each wash restores, not just what it costs, and the trend tells you when to stop.
- On a heavy-dust site, the wash cycle itself is a running cost worth setting against a new unit.
Questions this case answers
Why does chemical washing help less each time on an old unit?
How do I decide between washing an old aircon again or replacing it?
Can a chemical wash fix collapsed or corroded fins?
Should I stop servicing a unit that is due for replacement?
Ready to get started?
Tell us what’s going on. Symptoms, setup, photos, anything we should know. We’ll assess and come back with the right next step.