The purpose of BESA testing is to enable the performance of commercially available HIUs to be evaluated under operating conditions associated with the UK. The test regime is focussed on twin-plate HIUs with heating and DHW loads typical of new flat developments and small to mid-sized houses. This is to provide comparative information to the designers and developers of heat networks. 

Further benefits accrue to the operators of heat networks, who gain by having data which enables them to recognise anomalous performance. As regards the HIU manufacturers, it is hoped that test results will inform their programmes for continuous improvement. 

The BESA HIU test procedure is based on a well-established test method used by the Swedish District Heating Association, or RISE.  This test programme calls for static testing of space heating, as well as dynamic testing of hot water performance. Part of the testing takes account of Volume Weighted Average Return Temperature (VWART). 

An aspect which receives close attention is HIU response during periods of no load, (keep-warm mode). To satisfy the pass criterion, a DHW delivery temperature of 45˚C must be achieved within 15 seconds of tapping. The keep-warm function is also tested after an 8-hour interval following last draw-off. 

Test results are passed back individually to HIU manufacturers, for assessment and for them to decide whether release should be made to a wider audience. Thus, it is the case that although many HIUs are submitted for testing, not all corresponding results are in the public domain!