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Energy awareness and compliance are vital

The subject of regulations and their implications could easily keep a group of air conditioning installers occupied for some time. Just discussing the existing, recently updated and forthcoming changes alone could easily take up several hours of discussion.

The next major deadline is in July, when it becomes a legal requirement for all individuals carrying out operations covered by the F-Gas Regulations to be officially qualified to do so. Industry experts are advising those not already booked onto a course to enquire about availability to avoid a last-minute rush.

New regulations

Energy management specialist energyTEAM’s Brian Rickerby describes how Part 5 of the Energy Performance of Building Regulations, which implements Article 9 of the European Energy Performance of Building Directive, now requires all air conditioning systems with a rated output of more than 12 kW to be inspected by an accredited engineer at intervals of not greater than five years.

The inspection deadline for such systems was 4 January, he points out. Buildings with air conditioning systems over 250 kW should have had their first inspection completed by January 2009.

The rated output of an air conditioning system is the total rated output of all systems within a building, irrespective of whether the individual units are linked to a common control system.

This means that even low-capacity ‘through the wall units’ and split systems will need to be assessed where the total cooling capacity in the building exceeds 12 kW.

The penalty for not being able to produce a certificate on request is £300, but the costs to the business of running inefficient systems could be much higher. However, Mr Rickerby continues, skilled air conditioning assessors will save you money.

They will identify the best methods for improving equipment efficiency to help the client or end-user save energy, increase equipment lifecycle costs and provide conditioned air to a space that is controlled accurately with minimal fluctuations in temperature and air speed.

The inspection process required under the EPB Regulations will examine the refrigeration equipment and air movement systems that are part of air conditioning systems, as well as their controls.

Many air conditioning systems are found to be providing far too much air flow and cooling/heating duty than is actually required.
Reducing the fan speed and frequency of refrigeration cycles will reduce the amount of electricity being absorbed by the compressors and fan motors, which will make significant savings over a short period of time if the air conditioning is used constantly.

From hospitals to small offices and shops, most air conditioning systems are not being operated or controlled as efficiently as they could be.

An inspection will also review maintenance procedures, frequencies of service visits and filter changes, along with F-Gas regulations, and compare them with current good practice and legislation.

In addition, an inspection will highlight poor housekeeping and control of the systems, and recommend suitable methods of daily operation to ensure that the systems operate efficiently and cost-effectively.

Environmental impact

Daikin UK’s Simon Keel (pictured) says headline statistics on the global warming potential (GWP) of HFC refrigerants can be misleading. They indicate that refrigerants with a high GWP used in the provision of renewable energy by heat pump systems outweigh the benefit of the carbon dioxide savings they achieve. But is that correct and how can we prove it either way, asks Mr Keel.

The problem is that, very often, equipment is driven by a refrigerant that, weight for weight, is many hundreds of times worse for the atmosphere than CO2.

However, it would be bad science to condemn one system and install an alternative that uses refrigerant with a very low GWP without a close look at the two.

The British and European Standard BS-EN378 enables us to calculate the total equivalent warming impact of a system. This regulation looks at all the factors involved with an installation and works out the total quantity of greenhouse gases, or their equivalents, that are released over a period of time.

It is this calculation that is important when specifying or installing a system - not just the headline figures. As it is a mathematical calculation, it only reflects the facts that have been entered into the equation, says Mr Keel. It has no preference about one system or refrigerant over another.

However, by using such an equation, it can be seen that even when we consider the direct carbon impact of any potential refrigerant leakage (which might theoretically occur when using a refrigerant such as R410A) and add this to its indirect carbon emissions (which are far lower than many alternatives), the lifetime carbon emissions may well be significantly less than using an apparently lower-GWP refrigerant such as CO2, which is nowhere near as efficient and responsible for far greater carbon emissions at power stations during its operation.

So to look at headline figures in isolation is misleading. In order for a system to have the minimum global warming impact, it is vital to look at the bigger picture. Perhaps any proposed phase-out of HFCs should wait until better alternatives that are thoroughly practical, plentiful and fully optimised are in use.

Energy-efficient cooling

Walter Meier’s applied products manager Dean Ward says although there are often attempts to design buildings without air conditioning, the fact is that many modern buildings with high internal heat gains require some mechanical cooling. The important thing, therefore, is to ensure that any such comfort cooling is as energy-efficient as possible, at all times of day and all levels of occupancy.

Fortunately, achieving this is considerably easier when modern technologies are deployed to full effect, Mr Ward continues - backed, of course, by tried and tested engineering principles.

A case in point is the Turbocor centrifugal compressor that is now available in some brands of air-cooled and water-cooled chillers. These variable speed controlled centrifugal compressors are able to respond very precisely to variations in demand, with a European seasonal energy efficiency ratio of up to 9.0.

In parallel, they also offer low cost of ownership compared with conventional compressors through the use of oil-free, non-contact magnetic bearings that eliminate wear and reduce noise and vibration.

The compressor is just one part of the equation, however, and it’s important to consider other factors, says Mr Ward.

Heat exchange efficiency, for example, is clearly important and can be enhanced by using new microchannel condensing coils with parallel flows. These have been shown to increase heat exchange performance by up to 45 per cent compared with traditional coils, and can be combined with Turbocor compressors to arrive at a very efficient solution.

Nevertheless, these chillers aren’t the best choice for every project and specifiers may often look to scroll compressors as an alternative. These offer very efficient part-load performance and we are now seeing higher capacity (up to nearly 1 MW), multiple scroll compressors with very precise step adjustment entering the market.

In other circumstances chillers with semi-hermetic screw compressors may be a more appropriate choice. So, as always, the important thing is to choose the best chiller to suit the specific requirements of each project.

In parallel, system design plays a key role. For example, depending on ambient conditions, free cooling may be used to meet all of the cooling demand or to pre-chill the water. Making maximum use of free cooling is facilitated by newer chiller designs that can enable some free cooling at ambient temperatures as high as 15 deg C.

The key here, Mr Ward concludes, is to maintain sound building services engineering principles and apply them to the latest energy-saving chiller technologies to arrive at the best all-round solution.