Air Handling Unit Design driven by Legislation
Tightened performance requirements for energy-related products forces design engineers, consultants & manufacturers alike to review and adapt unit selections to reduce component air velocities (pressure drop), increase heat recovery efficiency and lower overall unit energy consumption.
To generally satisfy Ecodesign Directives & Part L Specific Fan Power requirements, an increase in product space planning and unit cost must be budgeted for at building design stages, with unit design sizes having to be increased and internal components carefully selected to reduce unit working pressure drops and overall power consumption of the unit.
To clarify the scale of the design improvement required, when directly compared to 2015 legislation, current heat recovery unit selection cross-sectional areas must be typically increased by 60-70%, with subsequentially increased total unit costs of between 25-30% .
As the primary source of power consumption to any AHU, fan manufacturers are continually developing their product ranges to improve efficiency & thereby reduce power input levels.
When attempting to meet EcoDesign & Part L SFP requirements, the choice of direct drive electrically commutated (EC) fans has given consultants & AHU manufacturers a greater range of selection options to reduce fan absorbed power, which is generally the largest contributing power source within an air handling unit.
As an example, using multiple, smaller sized fan arrangements for any given duty can also assist in space planning & unit costs by the reduction of fan section lengths, with the inherent benefit of added duty resilience when compared to a single fan selection.
To satisfy and comply with the ever-increasing legislation on AHU’s, a ‘team effort’ is required by all parties involved with the project, with architects and building owners needing to allocate more plant and riser space within their buildings, M&E consultants needing to closely design ventilation systems to reduce ductwork losses, and suppliers needing to continue to provide innovation and technical expertise to deliver the project specific design criteria.
As we know, there are many factors effecting AHU compliance, but by all engaging as a team, the challenges posed by legislation can be achieved.