New chillers for old

Challenging times lie ahead for consultants. With the current financial climate driving some finance directors to batten down the hatches where budgets are concerned, consultants face the significant hurdle of persuading clients to opt for the best value rather than the cheapest option when it comes to chiller specification. Consultants must therefore make clients aware of other essential factors that are currently driving product choice while conveying that chiller replacement is not only desirable but necessary.

Soaring costs

Against the backdrop of a weakening economy, the cost of energy has soared in the past 12 months. During 2008 UK PLC has swallowed double digit rises in the cost of the gas and electricity and faces continued price and supply uncertainty in the months and years ahead.  

Alongside these pressures, refrigerant phase-out and a tougher refrigerant management regime are beginning to have an impact on the market.  

Introduced in 2000, the EU Ozone Regulation banned the use of ozone depleting HCFC refrigerants, such as R22, in new chillers and cooling systems. However, R22 remains a very common refrigerant in existing chillers and this Regulation will ban the use of R22 and HCFC drop in replacements such as R408 and R409 as top-up fluids for maintenance between 2010 (for virgin refrigerant) and 2015 (for recycled refrigerant). That said, the EU is already indicating its preference to bring this date forward and implement a total phase out by 2012.

As a result, more and more clients are waking up to the plain truth that, sooner rather than later, chillers using R22 and other HCFC refrigerants must either use alternative refrigerants or, ultimately, be replaced. 

It’s true that some HCFC users are waiting for a ban on recycled HCFCs to be introduced believing that there will be a supply of reclaimed R22 that they can use until this point. However, the high price of reclaiming R22 means that recycled R22 will only meet an estimated 15% of the servicing needs of the remaining installations.

At the same time, clients must also be made aware of the recently introduced European Union F-gas Regulations. F-gases or Fluorinated gases, which include HFCs, the commonest refrigerants used today, have a high global warming potential. The F-gas legislation was therefore brought in to help meet the EU’s Kyoto Protocol obligations by working to minimise the emissions of these gases and so reduce their impact on the environment.

New F-gas measures came into effect last year and apply to all static refrigeration and air conditioning equipment i.e. chillers. They impose legal obligations on operators of this equipment, with operators defined as the people or organisations that have actual power over the technical functioning of the equipment. Secure refrigerant containment is core to the regulation so it is necessary for clients to both prevent leaks and repair any leakage as soon as possible. A significant consideration for clients that own old leaky systems and the ongoing costs it takes to maintain them.

With recent technology developments and improvements in equipment design and performance, replacing old chillers with new high efficiency units can bring real cost benefits to clients. Replacement can also deliver guaranteed, longer term performance advantages than the higher risk, ‘stop-gap’ solution afforded by using alternative refrigerants in old chillers. As the phase-out begins to bite then R22 and other HCFC refrigerants will become less readily available on the market and much more expensive as a result. Additionally, if existing chillers are becoming unreliable and in contravention of F-Gas legislation by regularly leaking refrigerant, then the case for upgrading to a new chiller is even more persuasive for the clients.

Consider the EER

However, in a replacement scenario, selecting the most energy efficient chiller is not necessarily that simple, and there is certainly no one silver bullet solution for all applications. As a first step, it is necessary to consider each unit’s EER (Energy Efficiency Ratio), the ratio of cooling output compared to power input. 

Eurovent, the European Committee of Air Handling and Refrigeration Equipment Manufacturers, has set its own formulae to calculate EERs, making it easier to compare the performance of chillers manufactured by Eurovent accredited companies. Its classification for full load EER follows a similar path to the A to G approach to the Energy Labelling Directive, with the energy efficiency of chillers designated by Eurovent A or Eurovent B in catalogues and the Eurovent Directory of Certified products.

Yet, a chiller’s EER should not be considered in isolation. Reference to the chiller’s ESEER (European Seasonal Energy Efficiency Ratio), as set out by Eurovent will allow clients to compare the efficiency of one chiller against another under part load conditions.

Since the compressor is the single, largest energy consumer within any cooling system, the choice of scroll, screw or Turbocor centrifugal chiller is a key factor in defining the EER and ESEER. Chillers featuring the latest Turbocor centrifugal compressors, with their inverter-driven, permanent magnet motor and magnetic bearings, have recently grabbed plenty of headlines. Typically, traditional induction motors of this size are in the 92% efficiency range, but the Turbocor compressor’s permanent magnet DC motor provides an efficiency of between 96 to 97%. Yet, they are not necessarily the best option for all applications.

For those tasks requiring cooling capacities up to 350-400kW, then chillers featuring four or six independently operating scroll compressors are still very likely to be the most efficient selection. Matching a reducing load simply means turning compressors off – considerably more efficient than allowing compressors to continue to run in an unloaded state

For those projects where demand exceeds 500kW, then the choice is probably between a Turbocor or screw chiller. Where load conditions are going to be constantly above 70%, it is probable that a screw compressor chiller will be just as efficient as a Turbocor one, and considerably less expensive. (An important point for clients when discussing capital expenditure – although again to reap best value each application must be considered individually and clients must listen to the advice of the consultant). Where loads are likely to reduce for considerable periods to around 50%, Turbocor chillers will be significantly more efficient than screw.

Apply common sense

Common sense needs to be applied when selecting chillers by their capacity. The calculated cooling capacity, for example, will very likely include some margin of over capacity. The chiller selected will normally have a slightly higher than lower capacity than the calculated need, and the overall selection will be based on the peak load occurring on the hottest day of the year.  It is also likely that the selection criteria will be based on an ambient condition of up to 35°C. That may be fine for central London, but for more rural or northerly applications is that really necessary? In other words, in no time at all, clients could be overpaying for an oversized chiller which will cost more to operate and maintain throughout its lifecycle.

In short, for optimum efficiency and reliability, it is better to have a smaller chiller highly loaded than a larger one idling.

It should also be remembered that a chiller with a Eurovent certification can be absolutely relied upon to achieve its published capacity, a different situation to that which existed in the past.

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