If your HVAC only gets attention when alarms go off, you’re paying a premium for comfort. Unplanned downtime, spiking utility bills, hot-and-cold complaints—those are all symptoms of a system that’s being operated, not maintained. A well-built maintenance plan swaps firefighting for schedule-driven work that protects heat transfer surfaces, keeps sensors honest, and prevents small issues from becoming big invoices.
Commercial systems fail for boring reasons: airflow gets strangled, heat exchange degrades, or controls drift. The plan, then, should target those three realities first.
Start with airflow. Filters need to be sized correctly (no bypass around the rack), installed tight, and changed on pressure-drop—not guesswork. Fans deserve more than a glance. Belt tension and pulley alignment affect airflow and motor life; a belt that squeals in April becomes a no-cool call in July. Coil surfaces are next. Evaporator coils matted with dust kill capacity; condenser fins matted with cottonwood force compressors to run at higher head pressure. Clear the condensate, too—biofilm in pans and clogged traps trigger float switches and indoor leaks.
Controls are the silent culprits. Temperature sensors drift. Outside-air and mixed-air probes gum up. Economizers stick shut (or open) and make compressors do work the sky was ready to do for free. Test them. Calibrate a handful of zone sensors each visit and compare to a known reference. Where you run demand-controlled ventilation, verify CO₂ sensors annually so you’re not over-ventilating an empty floor or starving a busy one. If you’d like a simple scope to hand to a vendor, a concise overview of commercial HVAC maintenance services outlines the core tasks you should expect during planned visits. When you uncover failing contactors, capacitors, or a leaky coil during PM, pair that plan with responsive commercial HVAC service and repair so findings get resolved before they snowball.
This isn’t busywork. Federal guidance for building operators notes that basic operations and maintenance—coil cleaning, calibrated controls, functional economizers, and planned filter changes—are proven levers for performance, longevity, and energy savings. The U.S. Department of Energy’s Better Buildings resources highlight this preventative maintenance stack specifically for commercial HVAC equipment, underscoring how it improves efficiency and extends equipment life.
Intervals should follow run time, environment, and risk—not a calendar from a manufacturer’s brochure. A practical cadence that works for most offices, retail, schools, and light industrial:
Monthly at-a-glance checks (select units): Walk the critical gear—data closet splits, DOAS units, kitchen make-up air, high-complaint RTUs. Look for unusual vibration, icing, dirty sight glasses, and pan overflow. Read and log filter ΔP; you’re building a trend so changes aren’t random.
Quarterly work (most equipment): This is the muscle of your plan. Swap filters at a target pressure drop. Clean condenser coils before cooling season and again if debris is heavy. Inspect and tension belts; re-sheave if you’re perennially off design airflow. Exercise economizers and verify enthalpy/temperature setpoints. Calibrate a subset of zone sensors and discharge sensors. Open electrical panels and check lugs, contactors, and amperage against nameplate.
Semiannual tasks (shoulder seasons): Deep-clean evaporator coils with the right chemistry and a controlled rinse to protect downstream components. Test safeties—freezestats, smoke detectors, high-limit cutouts. Verify refrigerant superheat/subcool and inspect for oil stains at flare and braze joints.
Annual adjustments (tune, then trust): Rebalance outside air and supply air if loads changed (new tenants, densification, added equipment). Review BAS schedules versus actual occupancy and tighten up start/stop windows. Refresh sensor calibrations and replace outliers. Document coil conditions with photos so you can justify repeat cleaning or stretch intervals based on evidence.
Filtration deserves a note. If your fans and racks can handle it, stepping up to MERV 13 filtration (or an equivalent multi-stage strategy) noticeably improves capture efficiency of the 1–3 µm range common in offices. ASHRAE’s filtration guidance has recommended aiming for at least MERV 13 where feasible, with attention to fan capacity and sealing to prevent bypass—good engineering, not just good intentions.
Maintenance saves money when it targets physics, not guesswork.
Heat transfer (coils): A clean condenser runs at lower condensing temperature; compressors draw less power and last longer. Clean evaporators restore sensible capacity and reduce reheat. You’ll feel this on summer demand charges and winter reheat hours.
Airflow (fans and filters): When filters are changed on ΔP, not a fixed date, you balance IAQ with fan energy. Sealed racks cut bypass, which is free performance—no new equipment required.
Controls (sensors, schedules, economizers): Calibrated sensors keep supply-air resets honest. A working economizer provides free cooling during mild weather and shoulder seasons. If mixed-air temp doesn’t drop when dampers command open, you’re throwing away hours of no-compressor operation each week.
Failure prevention (electrical and drains): Tightened electrical lugs and replaced contactors eliminate nuisance trips. Clear drains stop pan alarms and ceiling leaks. Those two alone can shave dozens of after-hours calls per year in a mid-size office portfolio.
Indoor air quality is part of the savings story, too. Poor IAQ means complaints, productivity hits, and sometimes investigations. The EPA’s office IAQ guidance emphasizes that HVAC maintenance—ventilation set correctly, filtration maintained, and moisture controlled—is foundational to keeping occupants healthy and comfortable.
You don’t need a committee to start; you need a clean inventory and a short list of rules you’ll actually follow.
Inventory the fleet. For each AHU, RTU, split, DOAS, and exhaust fan, jot down tonnage, age, filter sizes and MERV, belt sizes, motor HP, and any known quirks. Tag criticality—what happens if this unit fails? A lab, surgery center, or security room gets a different cadence than a conference wing.
Baseline with a walkthrough. Open up a representative share of units. Photograph coils, pans, and electrical panels. Check damper travel by command. Compare several sensors to a calibrated handheld. You’ll come back with a punch list of fixes that pay back immediately (for example, a jammed return damper forcing infiltration during winter).
Calendar the work. Map monthly “eyes-on” checks for high-risk units. Schedule quarterly PMs on the bulk of the fleet. Slot condenser cleanings before cooling peaks and economizer tests during mild days. Make sure x-inch MERV-13s and belts are stocked so no one gets creative with substitutions.
Define what “done” looks like. Photo each coil before/after. Log filter ΔP at changeout. Record economizer command/response with mixed-air temps. If you’re using a vendor, put scope and deliverables in writing: coil cleaning method (no power washing into the cabinet), sensor calibration counts, and a timeline for quoting any corrective work discovered during PM.
Track a few simple KPIs. Don’t drown in data. Watch unplanned calls per 100,000 square feet, average filter ΔP at change, time-to-close for urgent alarms, and HVAC kWh per square foot. If the first three go down while energy intensity follows, your plan is working. If not, adjust intervals and tasks before you assume you need new equipment.
Example 1: Spring economizer tune-up on RTUs. Pick a mild day (50–60°F / 10–16°C). Command economizer to 100% open. Verify damper blade travel, check actuator operation, confirm mixed-air temp drops toward outdoor air, and ensure compressors stay off. Tag any units where mixed air doesn’t track outdoor air; that’s free cooling you’re missing.
Example 2: Filter strategy with ΔP triggers. Install differential pressure taps across filter racks on critical units. Set changeout at a ΔP that balances IAQ with fan horsepower (for many racks, ~0.8–1.0" w.c. total system static is a reasonable boundary; set your filter trigger accordingly). Record ΔP quarterly; if you consistently change too early or too late, adjust intervals.
Example 3: Coil cleaning that protects downstream equipment. On evaporators, use a non-acid foaming cleaner, shield electronics, and rinse with controlled flow to avoid flooding pans. Photograph before/after and log return/supply air temperatures pre- and post-clean to show restored ΔT.
Example 4: Controls calibration sprint. Once per year, pick 10% of zone sensors and verify against a calibrated reference. Replace or recalibrate outliers. Check discharge air sensors in the same sweep. You’ll see fewer hot/cold complaints immediately because the controller is finally “seeing” the real world.
One clear takeaway: a strong commercial HVAC maintenance plan is scheduled, measurable work—clean the surfaces that move heat, keep airflow honest, and verify the controls that make decisions. Do those three well, and comfort, reliability, and lower energy spend follow without heroics.
Use measured differential pressure and environment, not just calendar months. Many offices land on quarterly, while dusty sites, construction-adjacent spaces, or high-occupancy floors may need monthly. Always verify that the rack is sealed to prevent bypass, which undermines filtration even with a higher MERV.
On a mild day, command the damper fully open and watch mixed-air temperature trend toward outdoor temperature while compressors remain off. If mixed air barely moves or compressors still stage, suspect a stuck damper, failed actuator, mis-set enthalpy sensor, or poor linkage.
They’re a solid target if your fan and filter rack can handle the added resistance. Check fan capacity and monitor ΔP after install. If airflow suffers, step down to the highest MERV the system supports or use a two-stage approach to achieve equivalent efficiency while protecting fan horsepower.
Cleaning condenser and evaporator coils, confirming economizer operation, calibrating temperature sensors, tightening electrical connections, and aligning belts all reduce wasted energy. These measures restore design conditions so compressors and fans aren’t working harder than they should.
Base it on run time, space criticality, and dirt load. Critical spaces and rooftop gear exposed to debris may get monthly checks and quarterly deep work. Office AHUs in cleaner environments might be fine with quarterly PM and semiannual coil cleaning. Adjust with data: filter ΔP, coil photos, and complaint trends.
Before/after photos of coils, logged filter ΔP and replacement dates, amperage readings versus nameplate, economizer command/response with mixed-air temps, and notes on corrective items with part numbers. These details let you verify work and prioritize repairs.
It measurably helps. Keeping coils clean, airflow on spec, and electrical components within safe operating ranges reduces thermal and mechanical stress—the main drivers of early failure. That translates into fewer catastrophic breakdowns and more predictable replacement planning.