Air Handling Units 35
Integrating AHUs with HVAC systems Complete system integration should come as standard for optimal performance when
upgrading heating, ventilation and air conditioning systems, says Scott McGavin, product specialist, controls, at Daikin UK.
WHILE AIR handling units (AHUs), have been around for many years, it is becoming simpler to integrate these into the heating, ventilating and air conditioning system to provide a single HVAC solution, rather than various systems working in isolation. By combining heating, cooling, heat recovery, and air handling into one solution with all functions working together the most effective climate control solution can be provided.
The climate control within buildings can provide fresh air at the right temperature and humidity for the optimal health and performance of occupants and for effective machinery operation.
AHUs are available to meet the precise air input and stale air extraction requirements of any building, and provide this function as economically as possible. The AHU can supply air to other units, for instance to indoor units of VRV systems to provide a complete climate control system. The AHU can be a vital component of the total HVAC solution by providing air, either directly from outside or recirculated air, at precise temperatures for optimum comfort. This prevents cold air being brought inside which often produces draughts inside and results in unnecessary additional load on the heating, cooling, or air conditioning system.
Daikin UK supplies air handling units with plug-and-play design which can be configured and combined to meet precise requirements of any building. This enables the building manager to set parameters for the climate control system to reduce the onus on users to think about energy saving issues. Rapid returns on the initial investment can be made when systems are controlled to precise requirements. The integration of intelligent controls
into the climate control solution will provide user control and operational accountability. This allows the monitoring and adjusting of cooling and heating levels on a zone by zone basis within a building. Smart technology provides daily data and future energy projections by which system operation adjustments can be made in line with usage patterns. This technology can significantly reduce energy consumption in all types of buildings, from hotels and shops, to office buildings, leisure centres and schools.
Interlocking with other equipment saves energy and increases comfort. For example, interlocking air conditioning with keycard control systems and occupancy sensors to detect room occupancy status allows the automatic change of the setpoint or turn off of air conditioning in unoccupied rooms. These systems can also be interlocked with fire alarms, allowing them to perform an emergency shutdown of air conditioning and ventilation units.
Existing HVAC systems can be upgraded to incorporate the latest VRV systems, connecting these to the AHUs which may be in operation from a previous installation. When designing the new system care must be taken to ensure compatibility between the VRV system and the existing AHU.
Integrating VRV equipment into the HVAC system with existing AHUs can eliminate some of the heat exchange by using the AHU heating and cooling coils with refrigerant. This increases efficiency as the load on the VRV system is reduced. As VRV systems are primarily designed for indoor coil units, it is important to check the operating range with the product manufacturer when heating is
VRV IV heat recovery outdoor unit.
required, to ensure that the design load can be met. Daikin does not recommend using VRV systems to heat fresh air below 10°C. It is possible to heat below this level but performance is affected due to the relative humidity and the coil volume of the heat exchanger. The best efficiencies are realised when fresh air is heated above 10°C using heat recovery within the AHU by a plate heat exchanger or thermal wheel.
Providing air circulation from the VRV system to the AHU provides efficient use of the VRV technology. For further efficiencies indoor fan coil units can significantly increase the amount of heat recovery. When a system is able to offer heat recovery when it is in cooling mode the potential for huge savings can be realised. This is achieved by reusing recovered heat to warm the air delivered by the AHU.
By taking a wider view, looking at the requirements for the whole building, a fully integrated climate control system, which may include air handling units, should help to reduce whole life costs significantly and provide a comfortable environment.
A1Cbiss Visit ACR News online at
www.acr-news.com ACR News April 2014
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