Rooftop air-conditioning solutions have previously had a reputation for fast and easy specification and deployment, but not for having the desired efficiency and control.

Johnson Controls Building Efficiency Africa area GM Neil Cameron reports that the York Activa Rooftop range offers greater efficiency and is more environment friendly.

The York Activa Rooftop range is quieter and incorpor-ates improved technology, which allows for a more com- pact design and easy installa-tion and maintenance.

“Rooftop solutions remain highly attractive for outfitting small and medium-sized (up to 20 000 m2) buildings. For new buildings and even for refur- bishment or replacement units, they are easy to specify. They are factory-built and can simply be dropped on a roof and ducted into the building. However, in the past, the trade-offs have been a lack of efficiency and sophistication compared with larger, more expensive units. The York Activa Rooftop range changes that significantly,” says Cameron.

He explains that, originally, the rooftop units were considered a fairly entry-level cheaper solution where the environment and efficiency were not a great concern. The units that are manufactured today have been improved to the point where they are able to perform on par with, or even better than, some of the more sophisticated units.

Previously, Cameron says, the rooftop units were stand-alone units that could not be interfaced into building management systems (BMS). “Today, they come with BMS controllers, which essentially allow the unit to become more intelligent, providing the user with control over how the build- ing performs and, therefore, leading to greater flexibility.

A new panel control board (PCB) on the York Activa Roof- top range adds logic for greater control and enables control of the optional components such as heat recovery and variable- speed drive fans. The smart controller manages high-efficiency compressors and fans, which allow the rooftop units to efficiently achieve and maintain the required levels of comfort.

The medium-sized units improve efficiency by means of a tandem scroll compressor configuration whereby only one compressor is used at low loads.

An enthalpy wheel is able to reduce the running costs through increased efficiency, while simultaneously maintaining the indoor air quality at high levels by improving ventilation.

The electrical current return fan works with the indoor fan to balance the amount of air that is supplied to and removed from the space, while a differential pressure sensor provides easy setup and automatic maintenance.

Further, the triple input economiser system makes use of three probes to control return air, outdoor air and supply air. The PCB compares sensor values, which modulate outdoor and return air dampers, resulting in maximum efficiency. Coupled with quality sensors, payback is ensured within a few months, says Cameron. Indoor air-quality sensors measure poll-ution concentrations, with the economiser overridden if the pollutants exceed preset limits.

According to Cameron, the market is still a little bit slow because people have perceptions that the York Activa Rooftop solution is a cheaper product owing to preconceived notions.

He emphasises that the York Activa Rooftop range, with the new technology, while relatively new to the market, will change the way in which rooftop units are perceived, owing to its functionality and control.