Every commercial HVAC system gets maintained one way or another. The question is whether that maintenance is planned, or whether it happens in a rush after a chiller trips on the hottest day of July. A preventive maintenance (PM) program is the planned version: a documented set of inspections and tasks, carried out on a schedule, recorded, and reviewed so the program improves over time.
Well-run PM programs keep equipment reliable, protect comfort and indoor air quality, hold energy use close to design, and extend equipment life. This guide walks through how to build one, whether you manage a single office building or a portfolio.
Maintenance strategies
A good program uses more than one strategy, chosen to fit each asset.
| Strategy | How it works | Best suited to |
|---|---|---|
| Reactive (run to failure) | Repair or replace only after failure | Low-cost, non-critical items with easy replacement, such as small exhaust fans |
| Time-based preventive | Tasks at fixed intervals or runtime hours | Filters, belts, lubrication, inspections required by code or warranty |
| Condition-based | Tasks triggered by measured condition, such as filter pressure drop | Filters, coils, water treatment, items with variable wear rates |
| Predictive | Trend analysis to forecast failure, such as vibration or oil analysis | Chillers, large fans and pumps, critical equipment |
| Reliability-centred | Strategy chosen per failure mode based on consequence | Critical facilities such as hospitals and data centres |
Most buildings start with time-based tasks and add condition-based and predictive methods for their most important equipment. Pure reactive maintenance is reasonable for some assets but should be a deliberate choice, not a default.
Building the program
1. Create an asset inventory
List every maintainable asset: air handlers, rooftop units, fans, pumps, chillers, boilers, cooling towers, terminal units, heat exchangers, humidifiers, dampers, controls panels and so on. For each, record:
- A unique asset tag that matches the physical label and the drawings.
- Location, area served and system.
- Manufacturer, model, serial number and installation date.
- Key nameplate data such as capacity, motor size and refrigerant type.
- Filter sizes, belt sizes and other consumables.
Accurate tagging is tedious but pays for itself. Technicians waste a surprising amount of time searching for equipment that is not labelled or not where the drawings say.
2. Rank criticality
Not every asset deserves the same attention. Rate each one by the consequence of failure: life safety, critical operations such as an operating room or server room, tenant comfort, energy cost, or minor inconvenience. Critical assets get more frequent inspection, predictive methods and spare parts on site.
3. Define tasks and frequencies
Start with manufacturers' recommendations, code-required inspections, and ANSI/ASHRAE/ACCA Standard 180, which lists minimum inspection and maintenance tasks for common HVAC components. Our guide to ASHRAE Standard 180 explains how to use it. Adjust frequencies for local conditions: a rooftop unit near a highway or in a dusty industrial area needs more frequent filter and coil attention than one in a clean suburban setting.
Write each task so a technician knows exactly what to do and what counts as acceptable. "Inspect fan" is vague. "Check belt tension and wear, check sheave alignment, listen for bearing noise, record motor amps" is useful.
4. Choose a CMMS
A computerized maintenance management system (CMMS) schedules work orders, records completion and readings, tracks parts and labour, and stores asset history. Even a small building benefits from moving off paper and spreadsheets. Look for mobile access for technicians, easy recording of readings, and reporting that managers will actually use.
5. Assign resources
Decide which tasks in-house staff will perform and which go to contractors, such as chiller service, water treatment and controls. Contracts should reference the task list and require completion records in a format that feeds your CMMS.
6. Measure and improve
Review the program regularly. Look at failures that occurred despite PM and ask whether a task was missing, too infrequent or poorly done. Look at tasks that never find anything and consider extending their interval.
Typical task categories
Most HVAC PM tasks fall into a few groups:
- Filtration: inspect and replace filters, check frames and seals for bypass. See filter change strategies.
- Heat transfer surfaces: inspect and clean coils, check condensate pans and drains, check heat exchangers for fouling.
- Rotating equipment: belts, bearings, lubrication, alignment, vibration and motor current.
- Water systems: water treatment, cooling tower cleaning, strainers, glycol concentration, expansion tank pressure.
- Controls: sensor calibration, actuator stroke, damper and valve operation, review of overrides and alarms.
- Safety devices: freezestats, high and low limits, smoke detectors in ducts, fire dampers as required by code.
- Combustion equipment: burner tune-ups, flue inspection and safety controls, performed by licensed gas technicians under CSA B149 and provincial regulations.
Linking PM to controls and data
Modern building automation systems can tell you a great deal about equipment condition between scheduled visits. Trend logs show valves hunting, economizers stuck, and simultaneous heating and cooling. Fault detection and diagnostics software can automate this review and generate work orders. A strong program treats the BAS as a maintenance tool, not just a comfort tool. Our guide to fault detection and diagnostics explains how this works.
Measuring program performance
Useful indicators include:
- PM completion rate: the share of scheduled PM work orders completed on time.
- Planned versus reactive ratio: the share of maintenance hours spent on planned work. A program dominated by reactive work is under-resourced or poorly targeted.
- Repeat failures: assets that fail repeatedly signal a root cause that PM is not addressing.
- Backlog: overdue work orders, tracked by priority.
- Comfort complaints: a rising trend often points to maintenance gaps.
Avoid treating completion rate as the only measure. A program can show perfect completion while tasks are performed poorly. Periodic spot checks of completed work by a supervisor or third party keep quality honest.
Frequently asked questions
How often should HVAC equipment be serviced?
It depends on the equipment, its criticality and its environment. Filters may need attention monthly or quarterly, belts and bearings quarterly or semi-annually, and chillers and boilers at least annually with seasonal start-up and shutdown. ASHRAE Standard 180 and manufacturer instructions provide minimum frequencies.
Is preventive maintenance worth the cost?
For most commercial equipment, planned maintenance is cheaper than the combination of emergency repairs, premature replacement, energy waste and tenant disruption. The right level of PM varies by asset, which is why criticality ranking matters.
What is the link between PM and commissioning?
Commissioning establishes that systems work as designed. PM keeps them that way. When systems have drifted significantly, retro-commissioning can restore performance and reset the baseline for the PM program.
Key takeaways
- A PM program is a documented, scheduled and recorded set of maintenance tasks, reviewed and improved over time.
- Start with an accurate, tagged asset inventory and rank assets by criticality.
- Use ASHRAE Standard 180 and manufacturer requirements as the basis for task lists, then adjust for local conditions.
- Combine time-based, condition-based and predictive strategies rather than relying on one.
- Use BAS data and track planned versus reactive work to keep the program effective.
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