When you’re running service calls, the school environment stands apart from nearly every other commercial account. The combination of dense occupancy, strict air quality demands, and a fixed academic calendar creates a unique set of pressures. A seasonal strategy for a school situation isn’t just about changing filters and checking belts; it’s about understanding the rhythm of the building and the consequences of a failure during class hours. This article breaks down the comparisons and contrasts between the two main seasonal transitions—spring/summer cooling prep and fall/winter heating prep—so you can walk onto any campus with a clear plan.

The Core Differences Between School Seasons

Before diving into specific procedures, it’s critical to understand that a school’s HVAC load profile flips completely between seasons. In the cooling season, the primary challenge is managing latent heat from students and solar gain through large windows. In the heating season, the focus shifts to maintaining consistent temperature across sprawling, often poorly insulated spaces while combating dry air and drafts. The equipment itself may be the same—rooftop units (RTUs), split systems, or boilers—but the operational priorities are night and day.

Occupancy Patterns and Setback Scheduling

During the cooling season, schools often run a “flush” cycle early in the morning to remove overnight heat buildup, then maintain a steady temperature during occupied hours. The heating season, by contrast, requires a more aggressive morning warm-up to bring the building from a night setback of 55-60°F to a comfortable 68-70°F before students arrive. A common mistake is applying a uniform setback schedule year-round. In winter, a deep setback can lead to frozen pipes in perimeter zones, while in summer, a shallow setback wastes energy. Always verify the building automation system (BAS) or time clock settings for each season separately.

Air Filtration and IAQ Priorities

Indoor air quality (IAQ) is a year-round concern, but the strategies differ. In cooling season, dehumidification is paramount. High humidity in a school leads to mold growth, musty odors, and increased asthma triggers. In heating season, the concern shifts to particulate matter—dust, chalk dust, and dry skin cells—that circulates more readily when windows are sealed. Filter changes should be scheduled at the start of each season, but the MERV rating may need adjustment. A MERV 13 filter that works well for summer allergen control can create excessive static pressure in winter if the system is already struggling with cold air density.

Spring Transition: Cooling System Preparation

The spring transition is arguably the most critical for school accounts. You’re coming out of a period of low demand, and the system may have been idle for weeks or months. A rushed startup can lead to compressor failures, refrigerant leaks, and mold blooms that shut down classrooms.

Condenser and Evaporator Coil Inspection

Start at the outdoor condensers. Debris from winter storms—leaves, trash, and even rodent nests—can block airflow. Use a coil cleaner specifically rated for aluminum fins; avoid caustic chemicals that can degrade the coating. On the evaporator side, look for standing water in the drain pan. A clogged condensate drain is the number one cause of water damage claims in schools. Use a wet/dry vacuum to clear the line, and verify the trap is primed. If you find algae growth, treat with a pan tablet or a diluted bleach solution (one part bleach to 16 parts water).

Refrigerant Charge Verification

Schools often have multiple identical RTUs, making it tempting to assume they all have the same charge. Don’t. Check subcooling and superheat on each unit individually. A common mistake is overcharging a unit that has a slightly dirty condenser coil, which masks the real issue. Use a digital manifold with temperature clamps for accuracy. If you find a leak, document the location and assess whether it’s repairable in the field. For systems with R-22, be prepared to discuss retrofit options with the school’s facilities manager, as the phasedown makes repairs increasingly costly.

Economizer Operation

Many schools rely on economizers for free cooling during spring and fall. Test the economizer operation by forcing it into the “free cooling” mode. Check that the mixed air temperature sensor is reading accurately and that the damper linkage isn’t sticking. A stuck economizer that fails to close during high humidity can flood a classroom with moist air, leading to comfort complaints. Set the changeover to enthalpy control if the system supports it, rather than dry-bulb temperature alone.

Fall Transition: Heating System Preparation

The fall transition is about reliability in the face of dropping temperatures. A heating failure in a school is not just uncomfortable; it can force early dismissal and disrupt standardized testing schedules. The stakes are high, and the timeline is tight.

Heat Exchanger and Combustion Analysis

For gas-fired furnaces or boilers, the heat exchanger is the primary safety concern. Use a combustion analyzer to check CO levels in the flue gas. Acceptable readings are typically below 100 ppm for natural gas, but check the manufacturer’s spec. A cracked heat exchanger can introduce carbon monoxide into the air stream—a life-safety issue that requires immediate lockout and tagout. Perform a visual inspection with a mirror and flashlight, but don’t rely on it alone; a combustion analysis is more reliable for hairline cracks.

Ignition and Flame Sensor Cleaning

Schools accumulate dust and lint more than other commercial spaces. Over the summer, flame sensors can become coated with a thin layer of residue that prevents proper flame rectification. Remove the sensor and clean it with a fine abrasive pad or emery cloth. Avoid using sandpaper, which can leave scratches that accelerate future buildup. Check the igniter for cracks and verify the spark gap is within spec (typically 0.125 inches). A no-heat call in October is almost always traced back to a dirty flame sensor.

Pump and Valve Exercise

If the school uses a hydronic system, the pumps may have been idle since April. Exercise each pump by cycling it on and off, and listen for cavitation or bearing noise. Check the expansion tank pressure and ensure it matches the system’s static pressure. Zone valves should be manually opened and closed to verify they aren’t seized. A stuck zone valve in a classroom wing can lead to frozen pipes and extensive water damage. Document the position of each valve for the facilities manager.

Common Mistakes Across Both Seasons

Regardless of the season, certain errors recur across school service calls. Recognizing these patterns can save you time and prevent callbacks.

  • Ignoring the schedule: Assuming the BAS is correctly programmed is a trap. Always verify the occupied and unoccupied setpoints, the start/stop times, and the holiday schedule. Schools often have “teacher work days” that the BAS doesn’t account for.
  • Skipping the condensate line: In both seasons, a clogged drain can cause the float switch to trip, shutting down the system. This is especially common in spring when pollen is heavy, but it also happens in fall when leaves clog outdoor drains.
  • Overlooking belt tension: A loose belt in summer can cause the blower to underperform, leading to frozen coils. In winter, a loose belt can cause the heat exchanger to overheat and trip the limit switch. Check belt tension with a gauge, not by feel.
  • Failing to document: Schools have multiple stakeholders—facilities staff, principals, and district administrators. If you don’t document what you did and why, you’ll get called back for the same issue. Use a digital service report with photos.

When to Call a Senior Technician or Inspector

Not every issue is within the scope of a field technician. Knowing your limits is a sign of professionalism, not weakness. Here are the situations where you should escalate.

Refrigerant Leaks Requiring Major Repair

If you find a leak in a condenser coil or evaporator that requires brazing in a confined space, call a senior tech. Schools often have strict fire safety policies that limit the use of open flames. A senior tech may have access to nitrogen purging equipment and can coordinate with the school’s safety officer. Similarly, if the leak is in a system that uses R-22 and the repair cost exceeds 50% of a replacement, you should recommend a system evaluation rather than proceeding with a patch.

Carbon Monoxide Detection Alarms

If a CO alarm is triggered in a school, do not reset it and leave. Treat it as a life-safety event. Shut down the affected equipment, ventilate the area, and contact your dispatcher immediately. A senior technician or a licensed mechanical inspector should perform a full combustion analysis and pressure test before the system is returned to service. Schools are required to have CO detection in certain zones; if you find a non-functional detector, report it to the facilities manager as a code violation.

Electrical Panel Issues

If you encounter a tripped breaker or a blown fuse that recurs after resetting, do not keep resetting it. There is likely a short circuit or an overloaded circuit. Call a senior tech who can perform a load calculation and identify the root cause. Schools often have older electrical panels that are not arc-fault protected, and a recurring trip can indicate a dangerous condition. Never bypass a safety interlock or disable a disconnect to keep the system running.

Structural or Code Compliance Concerns

If you notice that a rooftop unit is not properly secured to its curb, or that the curb itself is rusted through, stop work and call an inspector. Schools are subject to strict building codes regarding fall protection and equipment anchorage. Similarly, if you find that a gas line is not properly supported or that the flue vent is obstructed, do not attempt a field repair. These issues require a licensed mechanical inspector to sign off on the correction.

Practical Takeaway

A seasonal strategy for school situations is about preparation and documentation. By separating your approach into distinct cooling and heating transitions, you address the specific risks of each season—humidity in summer, freeze-ups in winter—while avoiding the one-size-fits-all mistakes that lead to callbacks. Always verify the BAS schedule, clean the condensate line, and perform a combustion analysis on gas equipment. Know when to escalate to a senior tech or inspector for refrigerant leaks, CO alarms, electrical faults, or structural concerns. When you treat a school account with the same rigor you’d apply to a hospital or data center, you build trust with the facilities staff and keep the classrooms comfortable for the people who matter most: the students.