If your air conditioning system has an output of more than 12kw it must be regular inspected by an accredited air conditioning engineer, with TM44 frequency inspections to be within 5 years of each other.
Every system that has been installed on or after January 2008 has to be inspected within the first 5 years from the installation date. Not all air conditioning systems are affected by these TM44 regulations, however if you have an effective rated output of more than 12kw you have to ensure your air conditioning units are inspected, even if the individual units are less than 12kw but have a combined effective rated output of more than 12kw.