A cassette unit is an air conditioning unit whose indoor section is recessed into the suspended ceiling, showing only the air distribution grille below. It distributes cold air in 2 to 4 directions or a full 360°, serving commercial spaces of 20 m² (215 sq ft) and above.
Technically, a cassette unit comprises 3 systems: the ceiling-recessed indoor unit, the outdoor unit, and the connecting auxiliary system. It works on a closed thermodynamic cycle, with refrigerant circulating continuously between the outdoor and indoor units to absorb heat from the room air. On the market, cassette units are classified by airflow direction (1, 2, 4 directions, 360°), by operating mode (cooling only, heat pump), and by technology
With more than 20 years designing and installing refrigeration systems for seafood processing plants, industrial cold stores and commercial buildings across Vietnam, the technical team at Tan Long has brought together all its practical knowledge of cassette units in this article.
What is a cassette condenser?
A cassette air conditioner is a commercial air conditioner whose indoor section is fully recessed into the suspended ceiling, showing only the grille at the ceiling surface. The grille has one central intake and supply outlets on 2 to 4 sides, depending on each manufacturer's design. Unlike a residential wall-mounted unit, the cassette belongs to the local commercial air conditioning segment, serving large spaces with high ceilings.
Why is it called a “cassette”? The name comes from the square box shape of the indoor unit, resembling a cassette when seen from below. In Vietnam it is also called a ceiling-recessed air conditioner or a cassette-type air conditioner.
How a cassette unit differs from a wall-mounted air conditioner
A cassette unit differs from a wall-mounted air conditioner in 3 core respects: installation position, air distribution, and the condensate drainage mechanism.
A wall-mounted unit is fixed to the wall and blows in 1 direction. A cassette unit is recessed in the ceiling and distributes air in several directions. How does the condensate drainage differ? A wall-mounted unit relies on pipe fall for the water to drain naturally. A cassette unit has an integrated condensate pump that lifts the water and carries it out
| Criteria | Cassette condenser | Wall-mounted air conditioner |
|---|---|---|
| Installation position | Recessed in the suspended ceiling | Mounted on the wall |
| Airflow direction | 2 to 4 directions or 360° | 1 direction |
| Condensate drainage | Automatic pump | Requires pipe fall |
| Suitable floor area | 20–80 m² (215–861 sq ft) | 10–30 m² (108–323 sq ft) |
What components make up a cassette unit?
A cassette unit comprises 3 main systems: the ceiling-recessed indoor unit, the outdoor unit, and the auxiliary system connecting the two. The overall construction is similar to a wall-mounted air conditioner but larger and optimised for multi-directional air distribution. Below are the details of each part: the indoor unit, the outdoor unit and the auxiliary system.
Indoor unit
The indoor unit is the part recessed into the ceiling, responsible for distributing cold air into the room. It comprises: a squirrel-cage centrifugal fan creating multi-directional airflow, a copper-tube aluminium-fin heat exchange coil, a control board, air deflector blades, a dust filter, and a condensate tray with an automatic drain pump.
A standard indoor unit measures 256 × 840 × 840 mm. The grille measures 44 × 950 × 950 mm. The mini cassette range is smaller: 260 × 575 × 575 mm with a 51 × 700 × 700 mm grille. The indoor unit accounts for only around 5% of the whole system's electricity consumption, since it contains only the fan and the control board.
Outdoor unit
The outdoor unit comprises the compressor, an axial fan, the heat exchange coil and the expansion valve. This is the largest electricity consumer, at up to 95% of the system's total. Which part uses the most electricity? The compressor block in the outdoor unit, where the refrigerant is compressed from low pressure
The outdoor unit is built to withstand outdoor weather and needs no rain cover. However, from installation experience on projects in southern Vietnam, Tan Long's technical team has found that an outdoor unit placed in direct west-facing sun loses performance noticeably and has a shorter service life.
Auxiliary and connection system
Besides the indoor and outdoor units, the auxiliary system comprises: copper refrigerant pipework with 2 layers of insulation 10–13 mm (0.4–0.5 inch) thick, and separate power and signal cables to avoid interference. Some models integrate temperature, humidity and motion sensors, adjusting capacity automatically to the number of people in the room. Premium models also have a controller
How a cassette unit works
A cassette unit operates on a closed refrigeration cycle, tương tự nguyên lý bơm nhiệt. Refrigerant (refrigerant) luân chuyển liên tục giữa dàn nóng và dàn lạnh, hấp thụ nhiệt từ không khí trong phòng rồi thải nhiệt ra ngoài trời.
The cycle has 4 stages: the compressor raises the refrigerant to high pressure and high temperature, then the gas passes through the outdoor coil, releasing heat and condensing into liquid. The liquid refrigerant passes through the expansion valve and drops abruptly in pressure. At the indoor coil the refrigerant evaporates at low temperature, absorbing heat from the room air. The squirrel-cage centrifugal fan draws
During cooling, water vapour in the air condenses on the heat exchange surface and runs into the drain tray. The condensate pump handles this water by lifting it to drain outside, without relying on pipe fall as a wall-mounted unit does. From installation experience at seafood processing plants in the Mekong Delta
On heat pump models, the cycle reverses: the indoor unit releases heat into the room and the outdoor unit absorbs heat from outside. Some modern models integrate motion sensors, automatically reducing capacity or switching to economy mode when nobody is in the room.
Common cassette unit types on the market
Cassette units are classified by 3 criteria: the number of airflow directions, the operating mode, and inverter technology. Each type serves a particular kind of space and use.
By airflow direction, the market has 4 main forms. The 1-way cassette blows in one direction, suiting narrow rooms or corridors. The 2-way cassette blows from two opposite sides, for rectangular rooms. The 4-way cassette distributes air evenly from all 4 edges of the grille and is the most common for offices and restaurants. The round 360° cassette spreads air evenly in every direction, cooling
By operating mode there are 2 forms: cooling only, and heat pump (cooling and heating). By technology, inverter models save 30–40% of electricity against non-inverter models by varying compressor speed continuously instead of switching on and off.
| Type | Common capacities | Airflow characteristics | Suits |
|---|---|---|---|
| 1-way | 1,5–2,5 HP | Blows straight in one direction | Corridors, narrow rooms |
| 2-way | 2–3 HP | Two opposite sides | Rectangular rooms |
| 4-way | 2–6 HP | Even distribution from all 4 edges | Offices, restaurants |
| Round 360° | 2–6 HP | Spreads evenly in every direction | Lobbies, open spaces |
The common capacity range runs from 12,000 to 48,000 BTU/h (1.5–6 HP), suiting areas of 15 to 80 m² (161–861 sq ft) depending on heat load conditions. In addition, the slim cassette range has an indoor unit only 185–230 mm high, designed for refurbishments or ceilings below 2.7 m.
Advantages and disadvantages of cassette units
Cassette units distribute air evenly, save floor space and keep an interior looking clean. However, they require a suspended ceiling void of at least 300–500 mm (12–20 inches) and a higher initial investment than a wall-mounted unit of the same capacity.
On the advantages, the standout feature is multi-directional air distribution (4-way or 360°), eliminating the localised draughts common with wall-mounted units. Because the indoor unit is recessed in the ceiling, it takes no floor or wall space and does not affect the interior layout. The distance between indoor and outdoor units can exceed ten metres, allowing
On the disadvantages, the prerequisite is a suspended ceiling void deep enough — at least 300 mm for standard models. Spaces with an exposed concrete ceiling or a ceiling below 2.5 m are unsuitable. Installation costs 30–50% more than a wall-mounted unit of the same capacity, because the ceiling has to be cut, copper pipework routed, a condensate pump fitted, and the installer must be properly qualified.
Does a cassette suit a room with a low ceiling? The slim range is only 185–230 mm high and supports lower ceilings. However, from installation experience, the distance from the cassette grille to the floor should be 2.8–3.5 m so the cold air disperses evenly before reaching floor level. Below that, air distribution effectiveness falls noticeably.
Which spaces suit a cassette unit?
A cassette unit suits commercial spaces with ceilings 2.7 to 4 m high (9–13 ft), areas of 20–80 m², and high appearance requirements: offices, showrooms, restaurants, cafés, meeting rooms and hotel lobbies.
For offices and meeting rooms, a 4-way cassette of 24,000–36,000 BTU/h distributes air evenly for 15–25 people working without discomfort for those near the outlets. Restaurants and cafés usually choose the round 360° cassette for open spaces, combined with air purification and odour removal. Showrooms and retail outlets favour cassettes with
Why does a cassette suit spaces with many people? Multi-directional airflow disperses evenly throughout the room, avoiding the localised “hot spots” that a 1-way wall-mounted unit easily creates in rooms above 30 m².
Conversely, a cassette unit does not suit small bedrooms under 15 m², spaces with exposed concrete ceilings and no suspended ceiling, or outdoor and semi-open areas.
How to choose the right cassette unit for your needs
Choosing the right cassette unit means weighing 4 factors: the room's area and shape, ceiling height, actual heat load, and investment budget:
- The first step is estimating the capacity. Calculating BTU for a large room follows the rule: 600–700 BTU/m² for an ordinary office, 700–800 BTU/m² for a restaurant because of kitchen heat load and higher occupancy. For example, a 40 m² meeting room needs around 24,000–28,000 BTU/h.
- Second, check the ceiling space. The suspended ceiling needs a void of at least 300 mm for standard models, or 200 mm for slim models. Before installation, measure on site (not just from the drawing) and check the electrical, plumbing and fire protection services in the ceiling to avoid clashes.
- Third, choose the airflow direction to suit the room shape. Square or near-square rooms take 4-way or 360°. Long narrow rooms take 1- or 2-way.
- Finally, choose the technology. Inverter saves 30–40% of electricity in spaces used continuously for more than 8 hours a day. Non-inverter suits a limited budget or intermittent use.
| Acreage | Suggested capacity | Airflow type | Application |
|---|---|---|---|
| 15–25 m² | 12.000–18.000 BTU/h | 1–2 way | Small meeting rooms |
| 25–40 m² | 18.000–28.000 BTU/h | 4-way | Office |
| 40–60 m² | 28.000–36.000 BTU/h | 4-way or 360° | Restaurants, showrooms |
| 60–80 m² | 36.000–48.000 BTU/h | 360° | Lobbies, halls |
For spaces of 50 m² and above or with a complex heat load (cooking, industrial machinery, large west-facing glazing), Tan Long recommends consulting a professional installer for an accurate heat load calculation. At seafood processing plants, Tan Long's technical team includes heat released by production equipment and temperature differences
Frequently asked questions about cassette units
Does a cassette unit use more electricity than a wall-mounted air conditioner?
An inverter cassette unit consumes the same or less electricity than a wall-mounted air conditioner of the same capacity. Even air distribution brings the room to setpoint faster, reducing the time the compressor runs at high load. The indoor unit accounts for only 5% of total electricity; the rest is in the outdoor unit (compressor and fan at 95%). Inverter models save 30–40% against non-inverter when running more than 8 hours a day.
How does a cassette differ from a ducted unit?
A cassette distributes air directly through the grille under the ceiling, while a ducted unit pushes cold air through ductwork to separate outlets in several positions. A cassette is simpler to install and lower in cost, suiting a single room. Ducted units suit multi-room systems and hide all the equipment completely, but cost more and need a larger ceiling void for the ductwork.
| Cassette | Ducted unit | |
|---|---|---|
| Air distribution | Directly through the grille | Through ductwork to the outlets |
| Installation cost | Medium | High |
| Suits | Single rooms of 20–80 m² | Multi-room systems, whole buildings |
How often does a cassette unit need servicing?
A cassette unit needs servicing 2 to 4 times a year depending on how often it is used and how dusty the environment is. The maintenance procedure comprises: removing the grille, cleaning the filter, checking the condensate tray and drain pump, cleaning the heat exchange coil, and checking the refrigerant and signal wiring. At seafood plants in the Mekong Delta, where humidity and organic dust are high, Tan Long recommends servicing every 2 months rather than the 3 months manufacturers advise.
Important points when installing a cassette unit
Installing a cassette unit requires 4 conditions: an adequate ceiling void, a well-ventilated position for the outdoor unit, short copper pipe runs, and a properly qualified installer.
The suspended ceiling needs a void of at least 300 mm (measured on site, not taken from the design drawing). The outdoor unit goes outdoors in a well-ventilated position, out of direct west-facing sun. Copper pipe runs should be under 15 m (49 ft) to maintain refrigerant transfer performance. Power and signal cables must be separate and sized correctly for the equipment's capacity. Cutting the ceiling to seat the indoor unit requires a skilled
For advice on designing and installing a refrigeration system suited to your specific project, contact Tan Long's technical team by hotline or through the consultation form at tanlongvn.com.
See also:
- What is VRV cooling system? Advantages, disadvantages and operating principle
- What is FCU? Structure and operating principle of FCU
- What is AHU? Structure, operating principle, AHU parameters
Frequently asked questions about cassette units
What is a cassette condenser?
A cassette unit is a ceiling-recessed indoor unit whose body is hidden in the suspended ceiling, showing only a flat grille below, blowing air in several directions for even cooling across a large space.
What components make up a cassette unit?
A heat exchange coil, a centrifugal fan, an air filter, a condensate tray with drain pump, a grille with air deflector blades, and a control board.
How many types of cassette unit are there?
The common forms are 4-way, 2-way, 1-way and mini ceiling-recessed. Which one to choose depends on the floor plan shape and the available ceiling position.
What are the advantages and disadvantages of a cassette unit?
The advantages are appearance, even air distribution and taking no wall or floor space. The disadvantages are the requirement for a suspended ceiling of adequate depth, a higher cost than a wall-mounted unit, and the need for an access hatch for maintenance.
Which facilities suit a cassette unit?
Offices, restaurants, showrooms, meeting rooms and hotel lobbies — large spaces with a suspended ceiling and high appearance requirements.
Related pages
- Cold store condensers: construction, types and how to choose
- Horizontal Shell and Tube Condensers: Classification and Advantages and Disadvantages
- What is a condenser? Structure and operating principle
- Evaporators: construction, types and correct maintenance
- evaporative condenser
Doanh Nghiệp Đang Cần Khảo Sát, Nâng Cấp Hoặc Thiết Kế Mới Hệ Thống Lạnh Công Nghiệp?
Đội ngũ kỹ sư Cơ Điện Lạnh Tân Long với hơn 18 năm kinh nghiệm thực chiến chỉ đạo hơn 29 đại dự án quốc gia, cam kết tư vấn tính toán phụ tải nhiệt chuẩn xác, tối ưu hóa hệ số hiệu suất COP, chuyển dịch môi chất tự nhiên NH3/CO2 và tiết kiệm 20–30% chi phí điện năng vận hành.
Kỹ sư Nguyễn Toàn Thịnh (Giám đốc Kỹ thuật)
Hơn 18 năm kinh nghiệm thực chiến chỉ đạo tư vấn thiết kế và thi công hệ thống lạnh công nghiệp nặng, kho tự động ASRS và cấp đông IQF qua hơn 29 đại dự án quốc gia.
