Seasonal changeover checklists

Canadian buildings live through two very different seasons. A system that ran flat out heating at minus 30 C (minus 22 F) in January may be rejecting heat at 30 C (86 F) in July. Many systems handle the transition automatically, but plenty of equipment needs a deliberate changeover: cooling towers to be filled and treated, chillers to be started, boilers to be reduced or shut down, and freeze protection to be verified before the first cold night.

A changeover done well prevents a predictable set of problems: frozen coils in October, a chiller that will not start on the first hot day in May, and a cooling tower that sat stagnant for months. This guide provides practical spring and fall checklists that can be adapted to most commercial buildings.

Timing the changeover

Spring and fall shoulder seasons in Canada can swing between heating and cooling within a single day. Some practical points on timing:

• Do not wait for the first heat wave or cold snap. Start changeover tasks early enough to fix problems before they matter.
• Plan for overlap. Many buildings need both heating and cooling available during shoulder seasons, particularly with perimeter heating and interior cooling loads.
• Coordinate contractors. Chiller, boiler, water treatment and controls contractors book up quickly in spring and fall.
• Check the forecast. Freeze protection must be in place before the first hard frost, which arrives early in Edmonton and Calgary and later in Vancouver and Toronto.

Systems with automatic changeover, such as many VRF and heat pump systems, still benefit from a seasonal check of setpoints, controls and outdoor units.

Spring changeover: heating to cooling

Cooling towers and condenser water

1. Inspect the tower basin, fill, drift eliminators, distribution system and fan before filling.
2. Clean and disinfect the tower according to the water management plan before start-up. See cooling tower maintenance and Legionella control.
3. Reinstall any components removed for winter and close drains.
4. Fill the system, check makeup water and float valves, and verify water treatment equipment and chemical feed are working.
5. Check fan motor, belts or gearbox oil, and verify fan operation and vibration.
6. Confirm basin heaters and freeze protection are no longer needed or remain appropriately controlled.

Chillers

1. Review the off-season maintenance results, including tube cleaning, eddy current testing and oil analysis.
2. Confirm chilled water and condenser water flows are established and flow switches work.
3. Perform start-up per the manufacturer's procedure, usually by a qualified service technician.
4. Record operating data under load, including approach temperatures, and compare with previous seasons.
5. Verify refrigerant monitors and machinery room ventilation operate as required by CSA B52.

Air handlers and rooftop units

1. Inspect and replace filters as needed.
2. Inspect and clean cooling coils, condensate pans and drains, and confirm traps are primed.
3. Check air-cooled condenser coils on rooftop units and condensing units, and clean as needed.
4. Verify refrigerant circuits operate correctly at start-up, with normal pressures and superheat.
5. Check economizer dampers, actuators and sensors, and confirm the economizer high limit setting suits the local climate. See economizers: types, controls and common failures.
6. Verify fan belts, bearings and motor operation.

Heating systems

1. Reduce heating hot water temperature reset to summer settings, or shut down boilers if not needed.
2. Keep a boiler available if reheat or domestic hot water depends on it.
3. Turn off humidifiers where not needed and drain and clean them according to the manufacturer.
4. Disable snow-melting systems and verify sensor settings.

Controls

1. Switch seasonal modes, setpoints and schedules in the BAS.
2. Verify chiller and tower enable logic and outdoor air temperature lockouts.
3. Review and clear manual overrides left over from winter.
4. Check outdoor air temperature and humidity sensors against a reference.

Fall changeover: cooling to heating

Freeze protection

Freeze damage is one of the most expensive avoidable HVAC failures in Canada. Freeze protection should be verified before the first frost.

1. Test freezestats on air handlers with outdoor air, confirming they trip at the set temperature and shut down the fan and close outdoor air dampers.
2. Check preheat coil valves, pumps and controls.
3. Verify glycol concentration in glycol loops with a refractometer and adjust as needed. See glycol systems.
4. Check heat tracing on exposed piping and verify alarms.
5. Confirm outdoor air dampers close tightly and minimum outdoor air settings are correct.
6. Drain or protect coils and piping in systems that will be idle, such as unused cooling coils without glycol.

Cooling towers and chillers

1. Shut down cooling towers not needed for winter operation, drain the basin and exposed piping, and clean according to the water management plan.
2. For towers that will operate in winter, verify basin heaters, bypass valves, fan controls and ice management. See cooling tower selection and winter operation.
3. Shut down chillers not needed, following the manufacturer's procedure, and protect water-cooled chillers in unheated spaces from freezing.
4. Schedule off-season maintenance such as tube cleaning and eddy current testing.
5. Verify waterside economizer and free cooling controls where used.

Heating plant

1. Have boilers inspected and tuned by a licensed gas technician under CSA B149 and provincial requirements.
2. Test combustion safeties, low water cutoffs and flame safeguards.
3. Check venting, combustion air openings and carbon monoxide detection.
4. Verify heating pumps, including standby pumps, and confirm automatic changeover.
5. Restore heating hot water reset schedules to winter settings.
6. Check expansion tank pressure and system fill pressure.

Air side and terminal units

1. Check perimeter heating and reheat valves for full stroke.
2. Start and test humidifiers, and check water treatment and drains.
3. Inspect unit heaters, make-up air units and door heaters.
4. Replace filters if loaded from summer operation, smoke events or pollen.

Controls

1. Switch seasonal modes, setpoints and schedules.
2. Verify optimal start and morning warm-up sequences.
3. Test freeze protection alarms through to the BAS and to after-hours notification.

Making checklists work

A checklist only helps if it is used. Store checklists in the CMMS as scheduled work orders, assign each task to a responsible person, and record readings rather than just tick boxes. Compare readings season to season to spot drift. After each changeover, note any problems and update the checklist.

Seasonal changeover is also a good time to verify control sequences under real conditions. Seasonal testing during building commissioning applies the same idea to new buildings.

Frequently asked questions

Can changeover be fully automated?

Many controls tasks can be automated with outdoor temperature lockouts and seasonal logic, but physical tasks such as cleaning towers, verifying glycol and testing freezestats need people.

When should freezestats be tested?

Every fall before freezing weather, and after any controls changes affecting the air handler.

What is the biggest risk in changeover?

In fall, freeze damage to coils and piping. In spring, starting equipment that was not properly maintained or treated over winter, particularly cooling towers.

Key takeaways

• Plan seasonal changeovers ahead of the weather, with allowance for shoulder seasons when both heating and cooling are needed.
• Spring changeover focuses on cooling tower cleaning and treatment, chiller start-up, coils and economizers.
• Fall changeover focuses on freeze protection, boiler safety and tower winterization.
• Record readings and compare season to season.
• Store checklists as CMMS work orders and update them after each changeover.