Cassette air conditioning

What a ceiling cassette is

A cassette is an air conditioning indoor unit that fits into the ceiling. The body of the unit sits in the void above, and only a square fascia panel shows below, flush with the ceiling. Air is drawn up through a grille in the middle of the panel and blown out through louvres around the edge. Many cassettes send air out in four directions, and some in one or two, which makes it easy to spread cooling or heating across a large room without blasting anyone.

Cassettes are usually connected to an outdoor unit as a single split, a multi-split or part of a VRF system, with the refrigerant pipes, cable and condensate drain run through the ceiling void.

Where cassettes suit

• Open-plan offices and meeting rooms with suspended grid ceilings.
• Shops and showrooms, where walls are needed for shelving, displays and stock.
• Restaurants, cafés and bars, where even air across the dining area matters.
• Surgeries, clinics and salons that want a tidy, easily cleaned ceiling.
• Schools, halls and gyms, where a high-output unit in the ceiling can cover a large space.

Cassettes are less common in homes because few houses have suspended ceilings, but they can work in kitchen-diners, basements and extensions with a suitable void.

What the ceiling needs

A cassette needs a ceiling void deep enough to take the body of the unit, with room for the pipework, the drain and the cable. In a suspended grid ceiling, the unit usually takes the place of a ceiling tile or two, and is hung from the structure above, not from the grid. In a plasterboard ceiling, we cut an opening and fit the unit from the structure, with an access route for maintenance.

We also look at what else is in the ceiling: lights, sprinklers, smoke detectors, ductwork and cable trays. Cassettes need a clear area around them so the air isn’t blocked and so they don’t blow straight onto a smoke detector or a desk. On the survey we lay out the positions to give an even spread of air across the room.

Getting rid of condensate

Any air conditioning unit that cools also takes moisture out of the air, and that water has to go somewhere. With a cassette in the ceiling, there is rarely a natural fall to the outside, so the drain has to be lifted out of the unit and run to a suitable outlet. We plan the route, the fall of the pipe and the connection to the drainage on the survey. A blocked or failed drain on a ceiling unit can quickly mark a ceiling or damage stock, so the drain is checked on every service. Our article on condensate pumps explains how they work.

Fitting around your business

Most cassettes go into buildings that are already in use. We plan the work around your opening hours, protect desks, floors and stock and keep dust down when we open the ceiling. In multi-room projects we can work area by area, so the rest of the building carries on as normal. Electrical supplies are installed by our own team, as NICEIC approved contractors, so you don’t need a separate electrician.

Refrigerant and the rules

Cassette systems contain F-gas refrigerant, and in a commercial building the business is responsible, with its service technicians, for preventing leaks. Systems above the thresholds in the F-gas rules need periodic leak checks, set by the refrigerant charge in tonnes CO2 equivalent (GOV.UK: leak checks). If the total output of the air conditioning in the building is over 12 kW, it also needs a TM44 inspection at least every five years. We tell you what applies when we design the system.

Cassettes, cleaning and air quality

Because a cassette sits overhead in a busy room, keeping it clean matters. The filter behind the central grille catches dust and needs cleaning regularly, more often in shops, gyms and restaurants. The coil, the drain tray and the fan need cleaning on each service, so the unit doesn’t start to smell and the air keeps flowing in every direction. We show your staff how to remove and clean the filter safely, and we clean the rest on each visit. If someone has a concern about smells or dust from a unit, our article on air conditioning smells explains the usual causes.

Price and warranty

Cassette systems are priced after a survey, because the number of units, the ceiling type, the pipe and drain routes, access and working hours vary from job to job. You get a fixed price before work starts. VAT on business premises is at the standard rate. Warranty is the manufacturer’s, on its terms, which we explain for the model we quote. We install cassettes from Mitsubishi Electric, Daikin, Fujitsu, Panasonic, Toshiba, LG, Samsung, Mitsubishi Heavy Industries and Hitachi.