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Daikin Applied (UK) Ltd - Air Handling Units

Air Handling Units - AHUs - Fan Power - Ventilation Units

The Impact of the Energy Related Products (ErP) Directive on AHU selection

Daikin Applied UK Air Handling Unit Range from standard to fully bespoke Air Handling Units (AHUs), ranging from 0.3m³/s to more than 55m³/s.

The introduction of the Eco-Design European Directive along with the new Energy-Related Products Directive (ErP) have had a significant impact in the UK HVAC industry. The recent changes to the legislation and standards are to encourage manufacturers to improve efficiency and reduce energy consumption in Air Handling Units (AHUs), but its design impact can be limited with the benefit of Daikin Applied’s experience in AHU design and selection tools.

In the UK, before the implementation of the Eco-Design Regulation 1253/2014, the driver behind energy efficiency has been the increasing Part L efficiency requirements in terms of reducing overall SFP (Specific Fan Power). This has seen levels greater than 2.2 W/l/s reduce to 1.6 W/l/s and lower.

Manufacturers have been tasked to reduce fan power consumption via lower overall internal unit resistances using low pressure loss filter systems and lower component pressures through reduced unit velocity along with improved fan/motor efficiencies and AHU design. Whilst not all improvements can be achieved from the base AHU, designers are also tasked with closer system designs with reduced external resistances.

The new regulation – 1253/2014 covering the design of ventilation units was implemented in January 2016 and is in addition to the Part L requirements. This has a significant impact on Non-Residential Ventilation Units (NRVU). These are the legislative reference for AHUs. This regulation now imposes Heat Recovery on virtually all systems which are classed as Bi-directional Ventilation Units (BVU).

However, there are some exceptions; generally, if there is a mechanical extract, the rule of thumb should be to incorporate a Heat Recovery Systems (HRS).

Within traditional systems in the UK, there has been a large use of free cooling mixing arrangements coupled with air quality management to provide energy efficient air systems. However, under the new regulations, standard mixing is no longer considered efficient heat recovery. Heat Recovery Systems are now needed on most supply and extract systems.

The second area to impact on existing heat recovery systems is the increased efficiency requirements, which for Run Around Coil Systems has become a real challenge. Heat Recovery Efficiencies within the new legislation are also due to increase further in 2018 and when compared to the previous UK guidelines from Part L, the new standards have imposed significant increases:

Minimum Dry Efficiency Part L Eco-design from Jan 16 Eco-design from Jan 18
Plate heat Exchanger 50% 67% 73%
Heat Wheel 65% 67% 73%
Run Around Coils 45% 63% 68%

The new regulation also requires that all HRS systems shall have a thermal bypass facility.

For the calculation of HRS system devices installed within AHUs, the standard requires that the efficiency of the HR device is based on equal air flows and dry conditions. Most operational conditions generally have a degree of latent heat energy within either the supply or extract airstream and many systems have unbalanced airflow between supply and extract. However, the heat recovery device needs to be selected at the operational conditions with an iteration of proving calculations then conducted that simulate equal flow and dry conditions to meet the ERP Directive. Daikin Applied can run these calculations on all AHU selections.

The efficiency of the HRS based on dry conditions will also require a higher efficiency device to meet dry conditions. This then increases the heat transfer surfaces of the device with resultant increases in cost and operating pressures which will need to be mitigated to maintain SFP levels. This then can become a vicious circle of increased efficiency/pressure drop and/or increased size to reduce velocity and pressure drop while maintaining SFP levels. This is now making the optimisation of AHU selection critical in all applications.

Daikin Applied has more detailed information for all aspects on the application of the standard relative to AHUs. The continuing development of Eco-design in UK building design standards with new chiller targets for efficiency will be released from 2018 onwards. Daikin Applied can assist in all aspects of the HVAC system design.

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Daikin Applied (UK) Ltd
Head Office
Bassington Lane Industrial Estate
Cramlington
Northumberland NE23 8AF

Email Daikin Applied

(Cramlington): 01670 566159
(Dartford): 01322 424950

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