AHU vs FCU — what's the difference, and which one is in my building? Confused about what actually gets serviced.

Easy to mix up because both take chilled water and blow cold air — the difference is scale and what else they do.

FCU — Fan Coil Unit: a small unit serving one room or zone. Chilled water runs through a coil, a fan blows room air across it, a filter catches dust, and a drain carries away the condensate. You'll find them tucked above the ceiling in each room or as a visible cassette/wall unit. Apartments on district cooling almost always have FCUs — often one per room or area.

AHU — Air Handling Unit: a big central 'box' that conditions air for a whole floor or many zones and pushes it out through ductwork. It does more than an FCU — it usually pulls in fresh outside air, has heavier filtration, cooling (and sometimes heating/humidity) coils, larger fans with belts/motors, and dampers. A whole office floor, a mall, or a hotel runs on AHUs.

Which is yours? A single apartment or a small office = FCUs. A whole floor served from a central plant room with duct runs = an AHU (possibly feeding VAV boxes).

What gets serviced (so you can read the invoice): - FCU: coil clean, condensate drain clear + pan disinfect, filter clean/replace, check the control valve/actuator, and the chilled-water strainer. - AHU: the above at bigger scale plus fan belts and bearings, damper operation, the fresh-air intake/filters, and coil condition.

Manufacturers like Trane publish both. If the scope on your quote doesn't match what you actually have, that's the flag — worth a second opinion from a water chiller service in Dubai that can tell you your exact setup and the right service scope.