One area is too hot or too cold

Find every supply and return grille in the affected room and look at what is in front of them. Blocked returns and obstructed supplies are the most common cause of one room being wrong while the rest of the building is fine.

Stock stacked against a wall, a new partition, a bookcase, signage, a display or a stored pallet will do it, and none of it looks like an air conditioning problem to the person who put it there.

The checks worth doing before calling

Hold a hand or a tissue at each supply grille and confirm air is actually coming out. Do the same at the return and confirm it is pulling. A supply with no airflow and a return that is drawing normally point somewhere quite different from both being dead.

Check whether grille vanes or dampers have been closed. Somebody who found a desk too drafty two years ago closes a diffuser, and nobody ever opens it again.

Check for a ceiling void being used as a return plenum with something now blocking it, which happens after a build-out puts a full-height partition where the design assumed air could pass.

Check the thermostat: where it is, what is near it, whether it is in sun, above a fridge or a printer, beside a door, or controlling a zone it is not actually in.

What changed, and when

This is the most useful question and it is rarely asked. A zone that has always been wrong is a design or balancing issue. A zone that became wrong is a change.

New partitions or a build-out. Added equipment, particularly anything with a motor, a compressor or a heating element. A change of use, such as a store room becoming an office or a room gaining a lot more people. New signage or a display in front of a grille. Solar gain that arrived when a neighboring building came down or an awning was removed.

Note whether it is wrong all day or only at certain times, and whether it tracks the sun. A room that is fine in the morning and impossible after two in the afternoon is a solar and load problem rather than a broken unit.

Doors and pressure

Worth its own look. Air conditioning depends on air being able to move back to a return, and doors are part of that path.

A room that is only comfortable with the door open is telling you it has supply but no return. A door that has been draft-sealed, a transfer grille that has been blocked, or a new door with no undercut will all produce it.

In a building with a commercial kitchen, extract without adequate make-up air puts the whole space under negative pressure and pulls hot outside air in through every door and gap. Our article on why your kitchen is too hot covers that specifically, and it is the usual answer where the hot area is anywhere near a kitchen.

Where it is the system

If the airflow checks come back clean, the candidates are a failed zone damper, a control fault, a duct that has come apart in a void, an undersized run to that zone, or a unit that is not delivering full capacity. All of those need a contractor with instruments rather than a walk-through.

Where the whole building is struggling rather than one room, that is a different article: air conditioning that is not cooling.

Who is allowed to do what

The system is HVAC and Florida requires a licensed contractor for it at any job size. Balancing, dampers, ductwork, controls, refrigerant and capacity all sit there. TrionX coordinates that contractor and documents the visit.

The building side is ours and it is more of this job than people expect. Clearing obstructions, relocating stock and shelving, joinery and partition work around a grille, transfer grilles and door undercuts, blinds and solar shading, and the making good afterward are all performed directly by our own technicians.

Before you spend money on plant

Work through the free checks first, because a meaningful share of these are resolved by opening a damper, moving a pallet or taking a display off a return grille.

Where the answer does turn out to be the system, arriving with the airflow observations, the timings and what changed makes the diagnosis considerably shorter than a technician starting from a complaint that one room is hot.