The short answer
Service coils, drains and filters in spring; a system serviced in April behaves very differently in August from one serviced in July.
Air conditioning fails in the week it is needed most, because that is the week it is asked to work hardest. Almost every August emergency was visible in April.
How it is done
- Book the annual service before the season, not during it
- Coil, condensate tray and drain line together, never the coil alone
- Filters checked monthly through the summer, not annually
- Record the temperature split each service so decline is visible
Why it matters
A coil that is 30% fouled still cools, just slowly and expensively. You notice when the ambient temperature climbs, by which time every technician in the city is booked.
questions
Asked about this
The difference between the air going into the unit and the air coming out. Recorded each visit, it shows a system declining long before anyone feels it.
It is harder to do well and harder to book. The work is the same; the queue is not.
references
Background reading
- Air conditioning — Wikipedia
- Heat exchanger — Wikipedia