Most emergency HVAC calls we take in midsummer were preventable in April. A rooftop unit rarely fails without warning - it gets louder, it runs longer, the condensate line backs up, and then on the first 95-degree afternoon it stops. The cost difference between a scheduled filter and coil service and an after-hours compressor replacement is not small.
Quarterly
- Replace filters. In a building with heavy foot traffic or nearby construction, monthly.
- Wash condenser and evaporator coils. Dirty coils are the single most common cause of a unit running long and drawing more power than it should.
- Clear and treat the condensate drain line. A blocked line is what puts water through a ceiling tile.
- Check refrigerant charge and log it. A charge that drops every quarter means a leak, not a top-up.
- Inspect belts, bearings and electrical connections. Tighten what has moved.
Twice a year
- Test economiser operation. A stuck economiser quietly wastes a great deal of energy.
- Verify thermostat calibration against an independent reading.
- Inspect ductwork for disconnected runs and damaged insulation.
What to keep a record of
Log the date, the unit, the readings and the technician. When a unit reaches the end of its life you want a maintenance history to justify replacement rather than another repair - and if you ever sell or refinance the building, that record is worth having.
When to stop repairing
A rule of thumb: once annual repair spend on a single unit passes about half the cost of replacement, and the unit is past two thirds of its expected service life, replacement is usually the cheaper decision over a five-year horizon. Run the numbers on your own units rather than trusting the rule.