HEALTHCARE VENTILATION
of the biggest potential areas for savings is fans, as they account for around 40% of the total electrical energy used by ventilation systems.
Improved fan efficiency Recent technical advances have significantly improved the efficiency of fans and related motors. This has partly been driven by the Energy-related Products (ErP) Directive 2009/125/EC, and by substantial investment by manufacturers in the fundamental technology of impeller design, motors, and electronic speed controls. There is a presumption against use of older-style approaches, such as belt-driven fan systems, on both safety and inefficiency grounds. The default choice for fans is now electronically commutated (EC) motors, which offer significant improvements in performance and efficiency. As a result of their ability to vary fan speed according to the airflow needed, EC motor efficiency can be above 90%. When part of a system, EC fans consume up to 70% less energy than conventional, single- speed fans, delivering large reductions in emissions and running costs. In addition to the efficiency of individual components, the guidance highlights the importance of zoning and control strategy to overall ventilation system efficiency. Zoning has to take account of a number of factors related to how the treated building and specific spaces within it are used. For example, the guidance says zoning should be configured in the light of: n Occupancy over time. n Resilience requirements. n Fresh air / ventilation requirements. n Fire and smoke management strategy for the building or space.
Where the ventilation system is designed to provide full heating and / or cooling, the following additional factors also must be considered: n Internal or peripheral location. n Orientation of windows. n Variation of internal loads. n Level of control required.
Monitoring through a BMS In terms of control strategy, the guidance is clear: hospital ventilation systems should be controlled and monitored through a central building management system (BMS). It is no longer acceptable for individual items of equipment, or separate air-handling systems, to be equipped with local control only. No matter how good such controllers are, the big gains in efficiency come from a fully integrated, building-wide approach to energy management and environmental control. In the past, integration of local systems with a BMS sometimes presented challenges, due to the different communications protocols in use. Today,
Copper heat exchangers.
this has been greatly streamlined, and most of the mainstream manufacturers have made connection of equipment quick and easy. Another key element in optimising efficiency is specifying correct equipment capacities. HTM guidance advises that particular attention be given to the correct sizing of equipment at the design stage. Key to this is determining the true ‘in-use operating condition’. Overestimating this fundamental parameter at the outset will result in the selection of oversized equipment, that will be less easy to control, and result in higher energy use throughout the lifetime of the system.
Design and selection of set-points A connected issue is the design and selection of set-points. This can have a big impact on energy consumption, and requires careful calibration to ensure that the required conditions are met without overshoot and resultant excess energy consumption. Improving health and safety is another key driver of the updated
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guidance. It provides a new approach, based on the concept of the Ventilation Safety Group (VSG) in healthcare organisations. This follows a similar approach adopted in recent guidance on water and electrical safety in their own respective HTMs. A VSG is a multidisciplinary group with
responsibility for the safe and resilient operation of ventilation systems on healthcare premises. As part of a hospital’s governance structure, the group reports to a designated board member. The group typically includes an Authorising Engineer to act as an independent adviser, an infection prevention and control specialist, a representative of the authorised ventilation contractor, estates staff, clinicians representing individual departments, and finance staff. Other specialists may advise, as required.
Design of new systems As well as being responsible for all aspects of ongoing ventilation safety and resilience, the VSG’s remit includes the
In terms of control strategy, the guidance is clear: hospital ventilation systems should be controlled and monitored through a central building management system. It is no longer acceptable for individual items of equipment, or separate air-handling systems, to be equipped with local control only
April 2023 Health Estate Journal 61
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