TROX completes prestige project

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Published: 12 July 2019


commercial air conditioning air handling unit AHU London Trox UK
21 Dartmouth Street ©Nicholas Worley
TROX UK has supplied the air conditioning solution for a prestigious redevelopment project in London.

The 21 Dartmouth Street building is in the heart of St James’s Park, between Buckingham Palace and the Palace of Westminster, and offers 53,000 sq ft of office space.
Main contractor, mac group, and M&E services consultants, Max Fordham, required a solution which would combine optimum comfort conditions with outstanding environmental performance.

Air handling
At the heart of the system are two TROX X-CUBE air handling units. Each X-CUBE incorporates TROX’s integrated controls package, whereby damper actuators, pressure, temperature and humidity sensors as well as heat recovery control and fan control strategy are linked into the digital control network. Both units incorporate thermal wheels with pre-programmed strategies, selected to meet BVU efficiency in accordance of the ErP 2018 standard. This is the highest level of smart technology, combining pre-set algorithms, developed by TROX, to facilitate rapid reactions to changes in building load.

Zone-based VAV control
To deliver high levels of comfort and energy efficiency, the system utilises TROX’s X-AIRCONTROL variable air volume functionality. This is integrated with the X-CUBEs and with a TROX X-AIRCONTROL Zonemaster to address the needs of the different occupied spaces across the site. The building is divided into 20 X-AIRCONTROL zones, each of which has a TROX TZ Silenzio supply controller and a TROX TA Silenzio extract controller. The X-AIRCONTROL zone modules combine information from humidity, temperature and PIR sensors and ensure the perfect interaction of all air handling components in a room. The system recognises all digital sensors automatically and uses measured values to initiate control procedures.

The modules also collect information from air quality (VOC) sensors, which can be an invaluable tool in refurb projects, where large amounts of volatile organic compounds can remain present due to new furnishings/fittings and decorative work. Whilst the VOC sensor does not measure CO2 directly, it measures VOC’s exhaled by human beings which are directly proportional to the amount of CO2 exhaled. The VOC sensors detect many potentially harmful compounds (unlike simple CO2 sensors) and can communicate with the system to change the air flow rates, increasing them until acceptably low VOC levels are reached, and reducing again once the compounds have sufficiently dissipated.

 The 20 zone modules are integrated with the TROX X-AIRCONTROL Zonemaster. This intelligent controller provides a single point connection to the BMS for all of the zones via Modbus TCP or BACnet IP. For larger systems it is possible to connect five Zonemasters together, creating a network of up to 125 zones.

Energy efficiency and acoustics
The system supplied includes a fan optimisation strategy, controlling fan speeds based on damper blade position, which enables energy consumption to be reduced significantly. The Zonemaster monitors the position of all damper blades on the system and adjusts fan speeds in response to changing demands in each zone of the building, ensuring that fans are never operating at a higher level than necessary to meet demand. This provides significant energy savings compared to conventional fan speed control where the fan is commissioned to deliver a maximum system pressure at all times. Another advantage of the reduced system pressures/fan speeds is a reduction in noise.

Practical considerations
To ensure that the building was ideal for IT-intensive office premises, TROX Silenzio air supply and extract units were selected for each zone. These units can obtain an accurate airflow measurement without the requirement for lengths of straight air duct in advance of each module. This reduces the space and ducting requirements, making it easier to integrate the units in a congested ceiling space.

Ian Thomas, product technical manager – air products at TROX UK, said: ‘Increasingly, designers of HVAC systems for prestige commercial properties are exploiting the advanced control capabilities incorporated into the air handling equipment itself. This provides an extremely effective alternative to bespoke programming of the BMS, and delivers increased levels of zone-based control for occupants of the building. The 21 Dartmouth Street project is an excellent example of this approach, and we are proud to have played our part in the redevelopment of this prestigious site.’’