As a partner in the iSERVcmb project, MacWhirter Limited – a UK air conditioning contractor – have been undertaking Inspections of air-conditioning systems throughout the EU in various climatic conditions. The 44 systems inspected to date (out of 80 expected) have been shown to have a mixture good, poor or average energy consumption by the iSERV monitoring.
The Inspections allow the collection of data to establish if the iSERV prediction of performance is borne out by the actual operation and condition of the systems. The Inspections also allow us to identify any obvious defects or features that would give rise to the performances indicated, and to check that the description of system, activities and building corresponds to those in the iSERVcmb database.
We do not compare the Inspection findings to the monitoring at this stage, to prevent prejudicing the Inspection findings, but interesting trends have been found from the 44 inspections undertaken in United Kingdom, Greece, Austria, Portugal and Slovenia to date.
We have observed, for instance, a distinct contrast between Northern and Southern Europe as follows:-
Installed capacity
In Northern Europe, both Chilled Water and (Direct Expansion) DX systems alike often suffer from oversizing (with the attendant control and energy implications) – other than in perhaps the retail sector – by reason it seems of not appreciating or ignoring the need for basic room load calculations. In one case where a ‘one size fits all’ approach was used, this might not have been such an issue if inverter compressor models had been available at the time.
In Southern Europe, when there might have been overcapacity provided it was usually needed for flexibility of building/zone use. Multiple split DX systems were often installed which enabled load shedding, in contrast to using one large AHU, where by the fan input power would be excessive.
Maintenance
In Southern Europe maintenance visits appear to be more frequent, albeit they may be mainly minor inspections – monthly in respect of the retail sector and quarterly elsewhere. Whilst in Northern Europe, other than in the retail sector where monthly visits are the norm, the frequency of maintenance ranges from zero to twice annually. In parallel with our observations of far more issues with refrigeration systems in Northern Europe, this finding shows that the level of maintenance in Northern Europe should be re-assessed and both areas’ regimes would be enhanced if the ethos of the F-gas and ODS Regulations was embraced fully.
Visual evidence of refrigerant leak from an oil equalizing line on a compressor insulating jacket.
Energy Conservation Opportunities (ECOs)
Most of the Energy Conservation Opportunities flagged by the Inspections were found in Northern Europe i.e. four times as many as in Southern Europe. The main ones were:
• Maintain proper evaporating and condensing temperatures
• Consider modifying the supply air temperature (all air and, air and water systems).
• Replace or upgrade cooling equipment and heat pumps.
We can conclude, in general terms, that the Inspections to date reveal a wide range of operation of A/C systems, from good design, installation and maintenance, through to the other extreme. However, in all cases, the verification of energy efficiency in operation was most definitely absent.
Author: Dave Wright (MacWhirter Ltd)