01 / THE BIG PICTURE
Start with the essentials.
Air-handling equipment moves air across filters and conditioning components. An AHU commonly serves ducted areas; a fan-coil unit serves a more local zone. The exact components and arrangement depend on the installed design.
02 / STEP BY STEP
How the system works.
- 01
Air enters the unit
Return air, outdoor air or a mixture enters according to the system design.
- 02
Filters capture particles
Filters need the correct type, fit and maintenance so air can pass through as intended.
- 03
The cooling coil removes heat
Chilled water or refrigerant absorbs heat. Condensed moisture collects in a pan and drains away.
- 04
The fan delivers air
Air moves through ducts or outlets to the occupied space. Fan position can be before or after the coil.
03 / LOOK A LITTLE CLOSER
The details that matter.
Chilled-water coils
Water passes through the coil and is regulated by the installed control arrangement. Valves, actuators, strainers and water flow can affect cooling.
DX coils
Refrigerant passes through the coil as part of a refrigeration circuit. The outdoor system and refrigerant controls form part of the diagnosis.
Drainage is part of performance
Pans, drain outlets, traps and pumps must suit the unit. Poor access can make inspection and cleaning difficult, especially for concealed ceiling units.
04 / AT A GLANCE
Keep these distinctions clear.
| Component | Main job | Typical inspection focus |
|---|---|---|
| Filter | Airflow and particle capture | Clogging, gaps or an unsuitable replacement filter. |
| Coil | Heat exchange | Contamination, water-flow problems or refrigerant-side issues. |
| Fan | Air movement | Motor, drive, bearing or airflow-resistance problems. |
| Drain system | Condensate removal | Blockage, pump failure, pan condition or incorrect arrangement. |
THE KEY TAKEAWAY
Always preserve maintenance access in ceiling and ductwork layouts. A concealed unit still needs its filters, coil, fan and drain system to be reachable.
05 / COMMON QUESTIONS
Good questions to ask.
Can a clean filter solve every airflow problem?
No. Duct obstructions, closed dampers, fan condition and other restrictions can also affect airflow.
Does every AHU provide fresh air?
Not necessarily. Some recirculate air, while others handle outdoor air or a mixture. Confirm the actual arrangement.
Further reading
Daikin: air-handling unitsThis guide explains typical arrangements. Equipment selection, technical settings and repair procedures must follow the actual system design and manufacturer’s instructions.
