September is the turning point. Mornings are cool, and afternoons can still call for cooling. Leave the building in full summer mode and it starts the day cold and spends the afternoon catching up. Switch over too hard, and the next warm day leaves it short on cooling.
The first freeze is usually still ahead, and it doesn’t arrive on the same morning everywhere: outlying suburbs typically see it before the lakefront does. September’s job is heating startup and sequencing. Prove the plant starts, and keep summer and winter modes from working against each other. Freeze protection for exposed water is the October job.
What a Real Changeover Includes
- Heating startup by a qualified technician — light-off, venting, combustion air, safeties, pumps, and low-water protection, checked before the first morning you actually need heat. Switching modes in the control system is not the same thing.
- Outdoor air and economizers — dampers set for summer will under- or over-ventilate once nights turn cool. Make sure the sequence matches the season.
- Morning warm-up versus afternoon cooling — if the schedules overlap, both systems run and spend energy undoing each other’s work. Occupied hours, warm-up time, and cooling lockout need to agree.
- Last winter’s problem zones — perimeter rooms, entrances, and spaces served by rooftop units with weak heat. You already know these complaints. Walk them at startup, not after the first cold Monday.
- Leftover summer settings — unoccupied cooling setbacks and closed heating valves show up as cold calls the first week anyone notices.
Three Moves for the Changeover
Start the Heating Plant and Prove the Safeties
Do it on a planned visit, with your list of heating equipment in hand.
Set One Changeover Sequence
Outdoor-air dampers, warm-up, and cooling enable should match September weather, including the warm afternoons.
Walk Last Winter’s Complaint List
Do it while the technician is still on site. Those zones are your acceptance test.
A clean September startup makes the first cold week an ordinary one.