All air conditioning systems will soon have to be inspected regularly. Peter Grigg and Hywel Davies look at what procedures services engineers will need to follow to comply with the rules
This month, the government is set to publish details of Article 9 of the Energy Performance of Buildings Directive, which requires air conditioning systems to be inspected regularly. The inspection and its accompanying report aims to encourage good maintenance and efficient use of controls, while noting opportunities to reduce cooling loads or periods of operation of cooling equipment.
An industry working group with representatives from CIBSE, FETA, ACRIB, IOR, HVCA, BRE, BSRIA and SummitSkills is advising the Department of Communities and Local Government on the implementation of Article 9 in England and Wales.
The group is currently preparing a CIBSE TM (Technical Memoranda) that will set out a practical inspection procedure. This document, which is still being drafted, is likely to become the key route to compliance with the directive.
Under the directive, the inspection of air conditioning systems will be mandatory. This will, obviously, come at a cost to the building manager. However, it does not compel managers to act on any advice given. Therefore, the industry group felt the procedure should be kept at the simplest level necessary to minimise cost and disturbance yet enable poor performing systems to be identified and to provide useful advice.
The procedure will also need to take account of potential risks and liabilities to the inspector and manager, and the likely availability and skill levels of the people needed to carry out inspections.
The inspection should begin by reviewing records of the air conditioning system. In more recent buildings, useful summary information ought to be available in the building log-book; otherwise, system descriptions and commissioning records may be needed to find plant types, sizes and locations.
This information may indicate useful performance factors such as the specific fan power of air distribution systems. Records of “energy consumed” or “hours run” could help indicate unusual or excessive energy use, and so help in highlighting potential control problems.
The EPBD will require assessments for both Article 9 and for energy performance certificates. As these initiatives gather momentum, the records of both processes should be maintained so that information can be exchanged, saving time. Initially, however, records may be sparse, leading to additional costs to establish what is installed and where.
By requiring a review of maintenance records, confirmed if necessary by an initial examination of equipment, the TM allows a comparison with industry good practice. Visual inspection will also identify system components and confirms that the plant matches the records; if not they should be updated. The assessor should look for issues such as external damage or blocked heat exchangers, signs of leakage from refrigeration systems, and also check that the basic operation appears to be correct.
Where it is clear from the initial review a system is well maintained and controlled, then some aspects of the wider physical inspection may be omitted to cut costs.
System controls and settings offer the greatest potential for improvement and savings at little or no cost, for example by resetting the controls to reflect current use. The suitability of sensor types and their location and zoning of the system should also be assessed against the characteristics of the building and the current needs of the occupants, as there may be low-cost opportunities to improve system control. 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, the IT and other heat generating equipment in use along with 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 heat-generating 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 higher efficiency cooling plant that could be considered when systems are being renewed.
The associated report will need to identify the building and equipment inspected, and include:
- System records and documentation
- The state of maintenance compared with good practice, and recommendations to meet industry good practice where this appears deficient
- Low or no cost actions, such as clearing obstructed heat exchangers and making adjustments or improvements to controls
- Opportunities for reducing cooling loads or periods of operation, or co-locating IT equipment for targeted treatment, or the addition of solar control measures
- Opportunities to use alternatives such as free cooling, or using more efficient technologies such as variable speed fan drives
- 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 box story.
Article 9 refers to systems over 12 kW rated cooling output. However, the group has recommended that this figure is interpreted to 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 by 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.
The group has also helped develop the draft European Standard (prEN15420 Guidelines for the Inspection of Air Conditioning Systems) supporting this part of the EPBD. The draft is now at CEN national members’ formal vote stage, and should be available mid-2007.
This standard 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 the standard’s 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. This approach will not be adopted in England and Wales as it goes far beyond what is required by EPBD.
The working group’s guidance has been prepared specifically for air conditioning systems providing comfort cooling. These are defined as controlled services in Part L of the Building Regulations. Other systems may be installed to provide conditioned environments for equipment or processes, but these are often specialised and the processes and 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 and so they will not be covered in the TM.
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 is likely to start in January 2009, although it may be phased – possibly by size or complexity of systems. DCLG is finalising other administrative details at present, such as the frequency of inspection. A Statutory Instrument, expected to be laid in Parliament shortly, will set out the requirements, frequency and timetable for the inspections.
The draft CIBSE TM is nearing completion, with publication expected in spring 2007. For systems which are already well maintained and documented the inspection procedure will be relatively straightforward. The inspection should help inform operators on the status of their systems and also improve operational practice.
The reports will provide information to help those inexperienced building managers manage their air conditioning systems to get better performance, reduce energy bills and to cut carbon emissions.
Further improvements to the energy efficiency of air-conditioning - the Auditac project.
While the CIBSE TM will deal with the initial inspection, an EU-funded project, Auditac, is being developed to provide the tools and advice to enable specialists to identify practical measures to improve
the energy performance of air conditioning systems, writes BRE’s Roger Hitchen.
The project has now finished, and many of the results are available on the project website as downloadable guides, case studies, downloadable software and training information: www.eva.ac.at/projekte/auditac.htm
The software supporting tools:
- A training package on AC inspection, audit and renovation; what you should know if you own or manage an AC plant
- A database of case studies including different A/C systems and climate references
- Services allowing retrieval of past performance of equipment when Eurovent certified and default values for others. It is available at www.eurovent-certification.com
- A customer advising tool, provides information on the potential savings in AC system energy consumption that may be achieved through improvements on the building shell
- AC-Cost - allows you also to calculate the AC running costs when they are not separated from the rest of your bill.
The downloadable technical guides are:
TG 1: Are you sure you are not paying for inefficient cooling?
TG 2: Energy auditing of air conditioning systems and the EPBD: what does the new regulation say?
TG 3: System recognition guideline for field visit
TG 4: The AUDITAC method of preliminary audit for air-conditioning facilities.
TG 5: Analysis of energy conservation opportunities (ECOs) for air-conditioned buildings
TG 6: How to benefit from the Eurovent certification database and to retrieve past equipment data in the audit process
TG 7: A benchmarking guide for owners and energy managers adapted to air conditioning based on electricity bills
TG 8: Recommendations for manufacturers to make auditing easier
TG 9: Recommendations and competences for auditors and structures for training
TG 10: Case studies of improvements in AC systems
TG 11: A model-supported audit method
Building Sustainable Design
Peter Grigg works for BRE Environment, and Hywel Davies is at CIBSE