Where can I find information about the size of an air conditioning system?

The effective output of an individual air conditioning unit or system may be given on the rating plate attached to the unit. It may also be found in the operating and maintenance manual or on the manufacturer’s website. Alternatively, where the system is covered by a maintenance contract, the capacity should be known by the contractor and should be reported in the maintenance records they supply. Where there is more than one unit in a system, it may be necessary to aggregate the ratings shown on the rating plate of each unit.

The guidelines below are an approximate indication of typical figures for installed capacity for various spaces and may help you determine whether your system is within the scope of the regulations. Cooling requirements depend on a wide range of circumstances, including the fabric, location and orientation of the building, as well as the activities and the number of people occupying the building. Older systems are also likely to have higher rated outputs for a given floor area. Where more specific figures are needed, these should be calculated taking account of the particular circumstances of the building and its use.

If it is not clear whether a building reaches the threshold, the installed capacity of the system must be determined by appropriate inspection, calculation and enquiries. In other, more specialised buildings, the wide range of factors which influence system capacity means that the capacity of these systems should be determined by a suitably qualified person. If the information is not already available, the size of the system should be determined on a case-by-case basis.

For larger systems, a central cooling system serving an office building of 2,000m2 is likely to be 250kW rated output. Cooling systems serving meeting rooms which may be used by large numbers of people, such as council chambers, may exceed the 250kW threshold for lower floor area.