XBOXER Hybrid Development

Adam Plimmer, Design Engineer

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XBOXER Hybrid airflow paths

XBOXER Hybrid is Nuaire's first move into the hybrid ventilation market. During development, our NPD team discovered issues with conventional hybrid design that required a solution, developed specifically for our range.


Hybrid ventilation, also referred to as mixed-mode ventilation, is a strategy almost exclusively found in schools. Hybrid systems introduce air into a space by both natural and mechanical means, using driving forces of the wind and stack effect in tandem with mechanical components to achieve better airflow.

Nuaire’s XBOXER Hybrid unit is based on a natural ventilation system with fans to aid mixing in colder weather and to achieve higher flow rates in hotter weather. As an expert in mechanical ventilation, Nuaire has approached product design from a unique point of view, with a focus on proving the mechanical side of the hybrid unit.

 

Original concept for XBOXER Hybrid
Fig. 1 - Original concept for XBOXER Hybrid

Before development began, Nuaire carried out a customer survey to gauge requirements for hybrid ventilation. Consultants and contractors gave feedback and the information was used to shape the development process. Early development of the unit started in January 2017. The original concept (Fig. 1 - Original concept for XBOXER Hybrid) used a typical hybrid ventilation method with supply, extract, intake and exhaust working as two pathways inside the unit. The unit was also designed with an internal damper to recirculate warm classroom air to temper incoming external air, mitigating draughts. The initial design of the unit featured side access. However, testing revealed that the controls being in the air path affected performance. The design was changed to bottom access, improving performance and making it easier for designers to fit the unit into a classroom.

As can be seen in Fig. 1, built-in mounting brackets were the original approach for installation. This changed in February 2018 to a separate mounting bracket which would be mounted to the ceiling, allowing for a simple two-stage installation. The addition of a separate mounting bracket hidden at the top of a unit post-installation would also allow the unit to blend more easily into a classroom environment. To complement this, the number of external fixings and rivets was reduced to provide a sleeker look.

Nuaire has invested in a top class, third-party AMCA accredited test laboratory which is calibrated annually and subject to BSI quality audits. The XBOXER Hybrid was treated as a mechanical unit for testing purposes; however, results were not as initially anticipated.

 

Typical hybrid in natural mode
Fig. 2 - Typical hybrid in natural mode

With the damper fully open, hybrids work as a natural ventilation unit (Fig. 2 - Typical hybrid in natural mode). The pressure differential across the fan draws fresh air in from outside and supplies it to the room, allowing the CO2-laden air in the room to be displaced and leave through the exhaust path. These results were to be expected.

 

Typical hybrid in recirculation mode
Fig. 3 - Typical hybrid unit in recirculation mode

However, in recirculation mode (Fig. 3 - Typical hybrid unit in recirculation mode), even with the damper opened slightly, the intake side of the fan overpowered the natural buoyancy of the room and began to draw air in from both the intake and exhaust paths, meaning no air was allowed to leave the space.

The recirculation path needed to be disconnected from the discharge path. In late 2018 the team started a new design.

 

XBOXER Hybrid in recirculation mode
Fig. 4 - XBOXER Hybrid in recirculation mode

The Nuaire design (Fig. 4 - XBOXER Hybrid in recirculation mode) separates the recirculation path from the exhaust path when the unit is in recirculation mode. This design is specific to the XBOXER Hybrid and avoids excessive negative pressure by isolating the exhaust path from the supply path. After testing this new design, the XBOXER Hybrid was finalised January 2018. As of Spring 2019, Nuaire has launched three units as part of the XBOXER Hybrid range. Two single units, XB-H130M and XB-H130S (for master/secondary configuration) and a double unit, XB-H260. These units will be available with all required controls for full BMS integration, room air quality sensors with traffic light display and a simple to use, but student tamper-proof, control switch.

Development of the range will continue. Through 2019 we will be working closely with our customers and looking at their specific requirements to develop the range further. As experts in mechanical ventilation, we are excited to see where hybrid will take us.


For more information on the Nuaire XBOXER Hybrid visit https://www.nuaire.co.uk/commercial/xboxer-hybrid. To discuss Hybrid ventilation strategy on an upcoming project, call us on 029 2085 8200.

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