What is the difference between four-way cassette, fan coil and central air conditioning?

“Four-way cassette”, “fan coil unit” and “central air conditioning” are not necessarily three mutually exclusive unit types. They may refer separately to the air outlet form, the terminal equipment and the overall system, so looking at only one ceiling outlet may not be enough to determine the full model.

1. Four-way air discharge: a common indoor unit type

Four-way cassette units are commonly found in shops and offices. The panel is fitted into the ceiling and blows air in four directions. The appearance of the panel does not tell you the structure of the unit above, the cooling source or the drainage method; these still need to be confirmed by brand, model and site equipment.

Cleaning requires consideration of the accessibility of the filter, heat exchanger, fan, water collection and drainage areas, and the ceiling height and working space must also be noted. Cleaning the panel does not mean the inside of the unit has been cleaned.

2. Fan coil unit: the terminal equipment inside a space

A fan coil unit uses a fan to move air through a coil for heat exchange and is commonly found in central chilled-water systems. The unit can be concealed in the ceiling and supply air through ducts and air outlets, and it may also be installed in other forms.

The air outlet, filter, fan, coil and drip tray may not be in the same location. If there is no suitable access opening, some parts may not be directly cleanable. Understand the equipment and access routes before quoting.

3. Central air conditioning: a more general term for the system

Central air-conditioning generally refers to a system that uses more centralized equipment together with multiple terminal units or air-supply systems to provide cooling to different areas. The term is used broadly in daily practice, and may actually involve chilled-water equipment, fan coil units, air handling units or other configurations.

Therefore, when people say "central AC cleaning," they must first state which part is being cleaned. Cleaning an indoor terminal unit should not automatically be taken to include the entire ductwork, main unit, water system, control system or other common equipment.

4. The same location can have multiple types of equipment at the same time

An office may use a central system for chilled water, together with different terminal units; it may also have separate AC units. The scope that a tenant can handle and the equipment managed by the building may also be different.

Before arranging service, confirm with the management office or facilities person in charge which areas can be accessed, the shutdown arrangement, and the work authority, so you do not arrive on site only to find that the equipment cannot be accessed.

5. What photos can be provided before making an enquiry?

• A full view of the indoor unit or air outlet, the surrounding space, and a model label photo that can be taken safely.
• Existing access panel location and equipment information; no need to dismantle the ceiling to take photos yourself.
• Number of units, ceiling height, work location and site type.
• Cleaning requirements, fault symptoms, and the period when the unit can be stopped or the site can be accessed.

6. What should I look at when comparing quotes?

Compare the model, quantity, cleanable parts, drainage handling and exclusions, rather than only comparing the price per air outlet. If the model is not confirmed, first provide the information for an initial assessment; the final scope will still be verified according to the actual equipment.

Current model charges and service scope availableCommercial AC cleaning services; do not apply listed prices for other models directly to a full central system.

How do I apply the guide to my own unit?

First check the brand, model and manufacturer’s instructions; this article is for initial assessment and enquiry direction only, and does not replace on-site diagnosis. Different models, work locations and existing issues affect the project scope, and you cannot directly copy the procedures from another unit.

View as neededServices、Actual work recordsorServiceForm FAQ. If there is electrical or working-at-height risk, stop handling it yourself. Do not reopen, dismantle, or climb up just to take photos.