"Twice a year" is the answer most facility managers have heard for rooftop unit (RTU) maintenance, and for a lot of buildings that's close enough. But it's a starting point, not a rule. The right interval depends on how hard the unit runs, what's on the roof around it, and what happens if it goes down.
What actually drives the interval
- Run hours, not calendar time. A rooftop unit conditioning a restaurant kitchen or a 24-hour operation racks up wear far faster than one serving a 9-to-5 office. Two identical RTUs installed the same week can need very different PM schedules a year later.
- Coastal exposure. Salt air accelerates coil and cabinet corrosion. Sites near the coast benefit from more frequent coil cleaning and corrosion checks, regardless of run hours.
- What's downstream. A unit tied to a server room, a medical office, or a commercial kitchen has a much lower tolerance for unplanned downtime than one serving a storage area. That changes how much you should spend on prevention versus how much you're willing to risk on reaction.
- Age and refrigerant type. Older units and units on legacy refrigerants are more failure-prone and worth checking more often, especially heading into summer cooling load.
A reasonable starting framework
Quarterly — kitchens, restaurants, medical/lab space, anything running near continuously, or any site where downtime has a hard dollar cost per hour.
Bi-annual — typical retail and office space with standard business hours and moderate load.
Annual, minimum — light-use storage, seasonal space, or units that are genuinely low priority if they go down for a few days.
What a real PM visit should document
A maintenance visit that doesn't leave a paper trail isn't much better than skipping it. Every visit should log refrigerant pressures, amp draws on the compressor and fan motors, coil condition, filter status, and belt/drive condition where applicable — tied to that specific unit, not a generic checklist. That history is what lets you catch a slow decline before it becomes a August afternoon breakdown.
We run PM on this exact cadence framework across our Orange County commercial accounts, with every reading logged to the unit through DaVinci Portal. See the tier breakdown on our maintenance plans page, or read more about RTU service and installs.