BESA TEST STANDARD FOR HIUS
HIU performance has a major impact on the overall performance of heat networks, both with respect to return temperatures and network sizing.
Monitoring and trials have revealed that some heat networks have failed to achieve their intended efficiency targets. The new BESA (British Engineering Services Association) UK Standard for Heat Interface Units was launched in late 2016, having been developed by industry experts.
The new standard is regarded as an important step towards improving the overall performance of British district heating schemes and its key objective is to enable the performance of different HIUs to be evaluated within the context of typical UK operating conditions, thereby enabling heat network developers to consider the performance of specific HIUs against design requirements.
Under the test regime, HIU performance is independently tested and verified against a set of tests which replicate “typical” UK operating conditions. The key output of the test is the calculation of the annual Volume Weighted Average Return Temperature (VWART), with this being a composite of estimations of the annual VWARTs for domestic hot water, space heating and keep-warm functions.
Volume Weighted Average Return Temperature (VWART)
The VWART is an estimation of the annual volume weighted average return temperatures for domestic hot water, space heating and keep warm function.
The results reflect the expectedimpact of the HIU in differentoperating modes, mimicking the demands they might expect toexperience across a year in a typical new build development.
A lower overall VWART represents a lower average annual return temperature from the HIU to the primary network and therefore a better performing HIU.