- If the refrigerant in the system is an HCFC (see below), then it needs to be replaced by the end if this year.
- If the total power of your air conditioning systems is 12 kW or more, then they must be inspected at least every 5 years. The regulations that specify this are the Energy Performance of Buildings (Certificates and Inspections) Regulations where this is buried in the middle as regulation 21.
Simply check the label on the air conditioning unit (the section outside, not the bits in the rooms). This will state the code of the refrigerant, say R22 or R410A. Check this against the list in Technical paper 10 available from http://www.strategicsafety.co.uk/Information.html .