Sizing a cassette to the floor area
Cassettes are sized by cooling output in kW (kilowatts), and a commercial space typically needs around 100 to 150 watts per square metre, more with big windows, crowds or a kitchen. As a rough guide, 2.5 to 3.6 kW suits a meeting room or small office, 5 to 7 kW a larger office or shop, and 10 kW and above an open plan floor or a busy restaurant.
Compact or full size panel
A compact 600x600 cassette fits the space of one standard ceiling tile and comes in outputs up to about 6 kW, while the larger 900x900 size needs a bigger opening and goes up to around 14 kW. At the same output, the larger cassette is working less hard, so it typically runs more quietly and more efficiently. Both blow air out in four directions, so they belong near the middle of the area they serve rather than against a wall.
Ceiling void, pipework and filters
Each cassette needs a ceiling void deep enough for its body, typically around 25 to 35 centimetres, plus refrigerant pipework to an outdoor unit connected by an F-Gas registered installer and a drain, usually fed by a built-in pump. The outdoor unit needs its own supply from a qualified electrician, and the largest models typically need three phase power. Clean the filters behind the grille every few weeks in dusty spaces and have the system serviced annually to keep running costs down.
