The most found air conditioning system, often referred to as a 'split system' consists of an indoor ceiling or wall mounted unit, linked to an exterior condenser by black insulted pipes that contain refrigerant. The condenser, whether linked to one or more interior units, is often a large white box mounted on a wall or flat roof that dispenses around 4 kilowatts (kw) of cooling. The regulations stipulate that where the cooling capacity of a building exceeds 12 kW, then an assessment is required. That is not where one unit has greater capacity than 12 kW itself but where the total of whatever units are installed exceeds that amount.
Larger systems can often be air handling units (AHU). This is a large exterior unit which will cool air and then distribute it around a building through ducting and louvred ceiling vents. As a rule, the cooling capacity of an AHU tends to be greater than a split system and where one or more exceeds the 12 kW threshold, then they too need to be assessed. Others can contain chillers to cool water and then distribute that to cool air in a zone.
The Chartered Institution of Building Services Engineers (CIBSE) mandates how an assessment will be undertaken. It is against their guide TM44 that we are regularly audited to ensure that our processes and standards are correct.
TM44 requires that we:
To do so we assess a system whilst it is running and calculate the 'cooling load' of an area, taking account of the presence of people and equipment, to determine whether it is of sufficient capacity to cope with demand.
Sampling is defined in CIBSE guide TM44 - Inspection of Air Conditioning Systems. It allows us to 'randomly' select some of the air conditioning equipment in a building for in-depth calculation as opposed to it all. However, we first have to be satisfied that all the equipment is in good working order and maintained to the same standard before we more closely focus on part of it.
In the case of simple split-systems, the conventions require that we calculate the effectiveness of a minimum of three systems or 10% of the number if there are more than 30 installed. However, where air handling systems are installed then we must calculate the effectiveness of the first ten and then sample others thereafter. For that reason, level 4 assessments can be far more complex.
Part 50 of the Energy Performance of Buildings (Certificates and Inspections) Regulations 2007, requires certification every five years in England, Scotland, Wales and Northern Ireland.