Preparing for the advent of air-conditioning inspections
Preparing for air-conditioning inspections — Hywel Davies.
Having spawned the 2006 Building Regulations, the Energy Performance of Buildings Directive continues to impact on the industry with the development of schemes for inspecting air-conditioning systems over 12 kW of cooling. Hywel Davies explains how new guidance from CIBSE will help the industry.The new Energy Performance of Buildings Regulations, which implement Articles 7 to 9 of the eponymous Directive in England and Wales, require inspection of all air-conditioning systems over 12 kW rated output. An industry working group comprising CIBSE, FETA, ACRIB, IOR, HVCA, BRE, BSRIA and SummitSkills has just completed the new CIBSE TM44, which gives guidance on meeting these regulations. It also gives practical inspection procedures for air-conditioning systems.
Complying with the new rules Engineers and energy managers responsible for these systems need to consider how they will comply with the new rules. For systems over 250 kW they have until January 2009 to complete inspections, and for smaller systems they have until January 2011. So what do they need to consider? The regulations require that the ‘responsible person’ should commission an inspection and receive and retain the inspection report. That person will need to obtain this from a suitably accredited person who is a member of a Government-approved accreditation scheme. Membership will require evidence of the competence of the personnel and that the employing organisation has proper procedures in place for undertaking inspections and issuing reports. Inspectors will therefore need technical guidance for the conduct of the inspection and preparation of the report. CIBSE TM44: Air conditioning assessments provides this technical guidance. Both the directive and Article 9 require assessments and inspections to give owners and operators information about the performance of their buildings and plant. The intention is to identify opportunities to save energy and cut operating costs by delivering information on system performance. Whilst the air-conditioning inspection will be mandatory, it does not compel anyone to act on any advice given. The working group therefore felt that the procedure should be kept at the simplest level necessary to identify poor performers, and to minimise costs and disturbance to operation, while still providing useful advice on improving system performance and efficiency.
Opportunities The proposed inspection and report aims to encourage good maintenance and efficient use of controls and to identify opportunities to reduce cooling loads or operating periods. It also takes account of potential risks and liabilities for the inspector and manager, and the likely availability and skill levels of those needed to carry out inspections. The first step is to review records of the air-conditioning system. In more recent buildings, this information should be found in the building logbook. Otherwise system descriptions and commissioning records may be needed to find plant types, sizes and locations. This information may provide useful performance factors such as the specific fan power of air-distribution systems. Records of energy consumed or hours run may indicate excessive use and potential control issues. As assessments for both Article 9 and for Energy Performance Certificates gather momentum, records of both processes should be maintained so that information can be used for both types of assessment. In the early days, however, records may be sparse, and there will be additional costs to establish what is installed and where. A review of maintenance records and an initial examination of equipment allows comparison with industry good practice. Where this comparison shows that a system is already well maintained and controlled, some aspects of the wider physical inspection may be omitted to keep costs low. However, where maintenance may not have been undertaken or information is missing, there may be a need to investigate more thoroughly. Visual inspection identifies system components, confirming that the plant matches the records; if not they should be updated. The assessor should look for issues such as external damage or blockage to heat exchangers, signs of leakage from refrigeration systems, and check that basic operation appears to be correct.
Controls Examining system controls and settings offers the greatest potential for low- or no-cost adjustments, improvements and savings. The suitability of sensor types, and locations and system zoning should be reviewed — taking account of the building and system type and the current needs of the occupants. Systems that allow simultaneous operation of both heating and cooling in the same space should be a particular concern. Rules of thumb are used to estimate the cooling load, current levels of occupancy activities being carried out, the IT and other heat generating equipment in use, and solar and other heat gains. This indicates the size of the system in relation to the load and whether there are opportunities to reduce these loads, perhaps by co-locating equipment in separate treated spaces or by applying solar-control measures. There may also be opportunities to use more efficient equipment such as variable-speed fans with relatively short payback times, or the manager may be informed of the availability of more efficiency cooling plant that could be considered when systems are renewed. The report will identify the building and equipment inspected, including the following. • System records and documentation.
• The state of maintenance compared with good practice, with recommendations for improvement if appropriate.
• Low- or no-cost actions, such as clearing obstructed heat exchangers or adjustments or improvements to controls.
• Opportunities for reducing cooling loads or periods of operation, such as co-location of IT equipment for separate treatment or the addition of solar-control measures.
• Opportunities to use alternatives such as free cooling or more efficient technologies such as variable-speed fans.
• The scope for opportunities that would need further examination or clarification by more detailed examination by specialists, including signposting to sources of further advice and support such as the advice tools developed in the EU funded AUDITAC project (see www.cardiff.ac.uk/archi/ research/auditac/index.html). The report should ideally be kept as part of the building logbook, so that the information is readily available to help others act on advice, prepare an Energy Performance Certificate and carry out the next air-conditioning inspection. The regulations require the responsible person to retain the report and, when they relinquish the responsibility due to a job move, building sale, or a change of tenant, pass it on to the next responsible person. Article 9 refers to systems over 12 kW rated cooling output. The Regulations include smaller packaged cooling units where the total capacity under common management in a building exceeds 12 kW. Such unitary, split and perhaps multi-split systems could form a class of equipment where the extent of inspection, the skills needed of the inspector and hence the associated training and qualification, could be reduced from that needed for more complex, centralised systems. The guidance offers a simplified, method and report format for these smaller systems. A draft European standard for inspection (prEN 15240, Guidelines for inspection of air conditioning systems) is now at formal vote and should be available mid-2007. It presents a flexible framework from which member states can derive their own procedures. Issues such as inspection frequency and the necessary skills and qualifications for inspectors are the responsibility of Member States, although informative annexes give suggestions. An associated draft standard (prEN 15239, Guidelines for inspection of ventilation systems) has also been developed to provide a similar framework for member states that wish to inspect natural and mechanical ventilation systems that do not include cooling, but this will not be adopted in England and Wales. The draft standard has much in common with the CIBSE guidance, which will be the everyday practical tool for use in assessments in England and Wales. The working group’s guidance has been prepared specifically for air-conditioning systems providing comfort cooling for occupants and defined as controlled services in Part L of the Building Regulations. Other systems installed to provide conditioned environments for equipment or processes are often individual and specialised. The processes and the systems that service them are often business critical and closely monitored. While the general principles of inspection may be applicable to such installations, different knowledge and skills may be needed to understand their design and control, and to make observations on sizing and opportunities for improvement.
Timetable DCLG is delaying the implementation of Article 9 so that suitable training and accreditation schemes can be set up to provide sufficient qualified inspectors. Implementation will start in January 2008, and systems over 250 kW must be inspected by January 2009. Systems over 12 kW must be inspected by January 2011. Thereafter inspections must be repeated no less frequently than every five years. CIBSE’s TM44 is due to published in June 2007. For systems which are already well maintained and documented, the procedure will be relatively straightforward and will inform operators and improve practice. The reports will provide the information to help those building managers with less experience of using and managing air conditioning to get better performance, reduce the energy bills and cut carbon emissions.
Hywel Davies is research manager with the Chartered Institution of Building Services Engineers.
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