Basic design flaws, user error and maintenance failings that result in poor operating efficiency can be addressed by appropriate legislation, says Space Air Conditioning's Mike Nankivell.
Many air conditioning systems do not perform as designed and, regrettably, building services are often not properly commissioned. This will contribute to an estimated increase in the average consumption of energy in commercial buildings of 35 per cent.


The result is not just a matter of the building being over or under heated, cooled or ventilated. Such conditions are not only undesirable for the occupants, but they also result in higher operating costs, which in turn increases the building's environmental impact in terms of carbon emissions.

Another important factor is that many design, installation, commissioning, maintenance and user/operator errors are frequently the cause of premature failure of the equipment itself.

The changes that can occur between system design and system operation can vary for a multitude of reasons. These can range from installation and commissioning issues, changes in building layout and use, poor or lack of maintenance, how the system is controlled or operated.

The introduction in 2008 of mandatory inspections for all air conditioning systems with a rated cooling output greater than 12 kW, as part of the implementation of the Energy Performance of Buildings Directive, can provide building owners and operators with essential information and guidance on the energy performance of their air conditioning systems. (Systems over 250 kW rated cooling output should have been inspected by January 4, 2009 and system rated above 12 kW must be inspected by January 4, 2011)

By identifying the potential for improvements in the energy efficiency of the systems, the air conditioning inspections, conducted by properly accredited assessors, will encourage actions that could dramatically reduce electricity consumption and operating costs.

The F-Gas Regulation's refrigerant leak checking regime is also helpful towards realising the optimum efficiency of ac systems.
The impact on air conditioning efficiency in the event of refrigerant leaks is dramatic. For example, a 15 per cent loss of refrigerant can equate to a 50 per cent drop in operating efficiency.

Regularised F-Gas leak checks and the legal requirement for leaks and their repairs to be recorded in a maintenance log will serve to reduce such efficiency losses.
In many cases, particularly with smaller or relatively uncomplicated systems, the inspections may simply recommend addressing the kind of elementary problems that can all too often be discovered. Here are just a few classic examples:

· Incorrect positioning of outdoor units - Inappropriate positioning of air-cooled condensing units in a cellar or restricted air space can starve the system of ambient air onto the condensing units and restricted discharge will cause recycling.

· Incorrect positioning of indoor units - For example, a cassette installed so close to a wall that the discharge pattern of the airflow is disturbed and can influence the room temperature sensor resulting in control issues.

· Dirty or corroded heat exchangers - Coil corrosion can lead to significant reduction in cooling capacity. A condensing unit coil that has never been cleaned will seriously impair its efficient operation.

· Dirty air filters - A fan coil unit filter clogged with debris is common yet simple to address, but the effect is a reduced air flow due to resistance with a consequent loss in performance.

· Inappropriate heat source - A heat source (such as a computer) positioned by the user adjacent to a room temperature sensor will restrict or prevent the system from switching to heating mode and or keep system in cooling unnecessarily. Routine maintenance should pick this up and it is relatively easy to resolve.

· Casual obstructions - One of the most common problems where the efficient operation of fan coil units is compromised is by post occupation fixed and casual obstructions eg using a fan coil unit as a bookshelf.
Each of these examples can lead to increased operating costs and a higher carbon footprint for the building.

Although the mandatory EPBD air conditioning inspections and F-Gas Regulations introduced extra burdens on building operators, the potential to improve the energy efficiency of our building stock will bring about enhanced occupancy comfort, help reduce running costs for building operators and help meet the government's carbon reduction targets.