The first warm week of the year is when most Calgary businesses discover their AC is not working the way it should. The unit runs, the thermostat is set, but the building is still warm. This is one of the most common calls we get starting in late spring, and the cause is usually something that built up over the winter while the cooling side sat idle.
Dirty condenser coils
This is the number one cause of poor cooling performance in commercial systems, especially rooftop units. The condenser coil sits outside and collects dust, cottonwood fluff, grease exhaust residue, and debris all year long. When the coil is dirty, the system cannot reject heat efficiently. The compressor works harder, head pressure climbs, and cooling capacity drops — sometimes dramatically.
On a rooftop unit, you can usually see the condenser coil through the cabinet panels. If it looks caked or matted, that is likely your problem. Coil cleaning is a standard part of seasonal maintenance and one of the easiest ways to restore cooling performance.
Refrigerant issues
Commercial AC systems do not consume refrigerant — if the charge is low, there is a leak somewhere. Low refrigerant causes the evaporator to starve, which means warm air coming out of the vents even though the system is running. You might also notice ice forming on the refrigerant lines or evaporator coil, which is a strong indicator of low charge.
Refrigerant leaks need to be found and repaired, not just topped up. Simply adding refrigerant without fixing the leak means you will be in the same situation again in a few weeks or months.
Thermostat and control problems
Sometimes the issue is not mechanical at all. A thermostat that lost its programming over the winter, a sensor that drifted out of calibration, or a control board that is not staging the compressor correctly can all make it look like the AC is broken when the equipment itself is fine. If you have a programmable or networked thermostat, check that the schedule, setpoints, and mode are correct before assuming the worst.
Airflow restrictions
Dirty filters are the most obvious airflow restriction, but they are not the only one. Closed or blocked supply vents, collapsed ductwork, or a failed blower motor can all reduce airflow to the point where the system cannot cool the space. If some rooms are cool and others are warm, the issue is more likely airflow distribution than the AC unit itself.
On rooftop units, belt-driven blowers can also lose performance if the belt is worn or slipping. A quick visual check of the belt condition and tension can rule this out.
Electrical and capacitor failures
Compressors and fan motors rely on capacitors to start and run. A weak or failed capacitor is one of the most common component failures in commercial AC systems. The symptom is usually a unit that hums or tries to start but cannot get going, or a fan that spins slowly. This is a straightforward repair when caught early, but running a compressor with a failing capacitor can burn out the motor.
When to call for service
If you have checked the thermostat, replaced the filters, and the system is still not cooling, it is time to call a technician. Running a system that is low on refrigerant, has a dirty condenser, or has an electrical issue will only make the problem worse and more expensive. Early-season AC problems are also much easier to schedule around than mid-July emergencies when every HVAC company in Calgary is booked solid.
YYC Mechanical services rooftop units, commercial HVAC systems, and split systems across Calgary. If your AC is not keeping up, give us a call — we will get it sorted before the heat really sets in.