Running air conditioning plant when it is either short of refrigerant or over-charged is a bit like running a car without enough water in the radiator. Sooner or later, something bad (and expensive)will happen.

With an under-charged system, the expensive bit begins to happen right away, as the plant runs significantly less efficiently than a correctly charged system. While the plant draws less electrical current, it runs for extended periods when it fails to achieve the same cooling or heating output. The same syndrome arises on many types of plant that are excessively overcharged with refrigerant.

With electricity prices rising by two-thirds over the past two years, and predicted to increase further, building owners and operators need to wise up to the haemorrhaging of money represented by their under-performing air conditioning systems.

In the longer term, running air-conditioning plant with insufficient refrigerant charge forces it to work longer and harder to achieve the required capacity — causing premature wear, component breakdown and reduced working life.

The big picture here is sobering. Many — dare I say, most — buildings operate well below optimum efficiency much of the time. An important part of this relates to the building services in general and air conditioning in particular. Poor maintenance and undiagnosed refrigerant loss (or excess charge) are the most common causes of underperformance and energy wastage. Similar problems arise where plant is not correctly set up for efficient and optimum performance.

Studies carried out on the Continent suggest that up to 90% of air-conditioned buildings operate below design specification. On this basis, there will be some nasty surprises when the results start coming out from the new mandatory inspections of building efficiency required under the Energy Performance of Buildings Directive (EPBD).

No one wants to occupy an inefficient building. It is expensive — in terms of both energy and reputation. For large companies and public bodies with corporate sensitivities, the requirement to display an energy rating on their buildings will be an all-too-public statement of their actual, rather than their declared, environmental credentials.

The EPBD highlights the significant contribution of air conditioning to the overall energy performance of buildings. Under Article 9, EU members are required to implement mandatory inspections for air conditioning, to evaluate and improve building energy performance.

In this country, this requirement is being implemented by the Energy Performance of Buildings (Certificates & Inspections) (England & Wales) Regulations 2007. This requires all-air conditioning plant over 250 kW of cooling to be inspected by January 2009; and all systems from 12 to 250 kW to be inspected by January 2011.

The inspections are intended to evaluate the efficiency and appropriateness of plant sizing in relation to the cooling/heating requirements of the building. Inspectors are also required to advise building operators on possible improvements to systems to enhance efficiency — including, where relevant, possible replacement of plant.

Conducting these inspections in the real world, however, will pose genuine difficulties for inspectors. Ideally, buildings would be fitted with energy sub-meters to the main air-conditioning components. Operators would have a building log book, with descriptions of the air-conditioning system, locations and specifications, and details of controls. This would give the inspector an objective starting point for the performance assessments.

However, as the Chartered Institution of Building Services Engineers concedes in Technical Memorandum 44, most buildings will not have this data available. Air-conditioning inspectors will therefore have to use a variety of less direct techniques on which to try and make an evaluation.

According to CIBSE: ‘Obtaining a good estimate of air-conditioning efficiency can be a very complex process, involving a considerable involvement in time, equipment and expertise.’ Therefore, it suggests, ‘Inspection will primarily be based on visual observations and non-invasive measurements.’

This approach has some fundamental drawbacks.

Delivering the EPBD requirements for air-conditioning inspections — the ClimaCheck instrument provides the means for non-invasive measurement of parameters such as COP, cooling and heating capacity, and compressor isentropic efficiency.

First, it uses unquantifiable techniques that are open to challenge. A negative evaluation could affect the future rentable value of the property, especially with energy costs escalating. It is a potential legal minefield for inspectors.

The second weakness of the proposed approach relates to the difficulty of ensuring consistency between inspections. Performance assessments based on a variety of subjective techniques that differ between buildings and inspectors cast doubt on the cross-comparability of results.

It is a straightforward matter to determine the efficiency of a domestic refrigerator or kettle. However, accurately assessing the efficiency of a complex air-conditioning system serving a large building is an entirely different proposition.

That, at least, has been the accepted wisdom until recently. Now, a new technique has been developed that makes it possible to quickly and precisely determine the actual efficiency of operating air conditioning plant — without intruding into the system.

It uses a new piece of technology called ClimaCheck, developed by Swedish thermodynamics pioneer, Klas Berglof. With this equipment, it is possible to gain a quantitative measure of the coefficient of performance (COP) of an operating air-conditioning system, which, using alternative approaches, would take weeks and hundreds of man-hours to achieve.

This instrument is being widely used by both end users and engineers in Scandinavian countries to provide reliable, consistent and comparable assessments of the performance of air-conditioning and refrigeration plant.

Leading UK supermarkets are now employing the technology to obtain quantitative assessments of the efficiency and performance of cooling systems — never before possible in relation to operating plant in real world, as opposed to test-bed, conditions.

A stark fact emerges from the accumulating experience with ClimaCheck. Klas Berglof explains, ‘It has become clear that most air-conditioning plant operates well below optimum efficiency. A significant proportion of installations is dramatically underperforming against design — whether due to poor maintenance, refrigerant undercharge, incorrect control, or mismanagement.’

A ClimaCheck instrument dynamically measures, calculates and records every key parameter of a running plant and then uses sophisticated algorithms to determine its operating characteristics.

It can be used with any type and configuration of plant, running on any type of refrigerant. Even parameters that are otherwise very difficult to measure such as COP (coefficient of performance), cooling/heating capacity and compressor isentropic efficiency can be readily determined — without the need to measure air or water flow rates or temperatures! Defects and faults in system components can also be pin-pointed, enabling users to anticipate future breakdown.

The system can be hooked up to a plant in 30 minutes, with results available immediately. A version for DIN rail-mounting can be permanently or temporarily installed, with results logged locally or remotely over the internet. There is an option of automatic alarm dial-out, in the event of a major problem, including detection of refrigerant loss!

As the initial wave of inspections begins, those equipped with this latest technology will be much better position to deliver what the EPBD requires. If challenged, they will able to provide objective proof of determined air conditioning efficiency and, possibly, defend controversial assessments.

Mike Creamer is managing director of Business Edge, which is the UK sole distributor for ClimaCheck.

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