What an HVAC Preventive Maintenance Contract Covers, and What It Misses
A preventive maintenance contract buys you scheduled attention: someone qualified looking at your equipment a few times a year. It doesn't cover the time between visits, and that gap is where most failures develop.
A typical commercial HVAC preventive maintenance contract includes two to four scheduled visits per year covering filter changes, coil cleaning, belt and electrical inspection, refrigerant checks, and thermostat calibration, priced per unit or per site. The visits are real value, but they're point-in-time by design: everything between them happens unwatched.
What does a typical PM contract include?
Contracts vary, but the core scope is fairly standard across the industry:
| Task | Typical cadence | What it protects against |
|---|---|---|
| Filter replacement | Every visit | Airflow loss, coil fouling, energy creep |
| Coil cleaning (condenser and evaporator) | 1-2x per year | Capacity loss, high head pressure, compressor strain |
| Belt, motor, and electrical inspection | Every visit | Sudden mechanical and electrical failures |
| Refrigerant charge check | 1-2x per year | Undercharge running the compressor toward failure |
| Drain line clearing | Seasonal | Water damage, iced drain pans |
| Thermostat and control check | 1-2x per year | Comfort drift, wasted runtime |
Beyond the checklist, a good technician notices the odd noise or the oil stain that no checklist item asks about. The difference between preventive and predictive approaches, and why commercial HVAC usually wants both, is one we've written up in predictive vs preventive maintenance.
What happens between visits?
On a quarterly contract, each unit is unobserved for roughly 90 days at a stretch; on a biannual one, closer to 180. A refrigerant leak that starts three weeks after a visit has months to run the compressor hot before anyone qualified looks at the unit again, and the failure it causes will arrive as an emergency long before the next inspection. On a twice-yearly contract, a unit spends more than 99% of its running hours unwatched. The visit catches what's visible on the day, and anything that develops in between only shows up when it breaks, at which point the bill looks like the one in emergency call-out vs planned repair.
Does monitoring replace a PM contract?
No. Monitoring is not maintenance: a sensor won't clean your coil. What continuous monitoring does is close the observation gap, checking each unit's behavior every few minutes instead of every few months, and make the contract you already have more effective. The visit becomes directed instead of a fixed checklist: the technician arrives knowing unit 3 has been losing capacity for two weeks and unit 5 is fine. A developing fault gets handled on the next scheduled visit instead of turning into an emergency. The data drives the maintenance, as we describe in what predictive maintenance actually means for HVAC, and the maintenance stays with your service provider.
What should you ask your service provider?
If you hold a PM contract today, three questions show where the gap is. What happens if a unit starts failing the week after a visit? How do you decide what to look at when you're on the roof? And can the contract use monitoring data if we have it? Good service companies increasingly say yes to the third, because a technician who shows up with a clear idea of what's wrong does better work. We've collected the fuller list in what to ask your HVAC contractor about monitoring, and if the cost question comes first, start with how much monitoring costs.
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