Developments in air conditioning systems are taking climate control for the office environment to new levels of comfort, energy management and design, says Richard Lockwood.
Although office air conditioning is first and foremost about providing comfortable working conditions, the need to balance user comfort with energy efficiency is a key design consideration. Air conditioning has become an almost universal requirement for modern offices, helping to attract high quality tenants and maximise rental potential.
While the cost of providing air conditioning may be recovered in part through rents, building owners are keen to keep operating costs as low as possible in the current economic climate. In addition to minimising running costs - and carbon output - office air conditioning needs the flexibility to deal with multi-tenancy situations, be able to integrate with a BMS, and offer future proof controls that meet the needs of individual users, without overriding a building's overall energy management objective.
One of the first considerations when designing an office air conditioning system is whether to specify a VRF type or chiller-based water system. Although the cost of purchasing VRF equipment may be marginally higher, cost savings can be made in system sizing, installation, and running costs. Simpler refrigerant copper piping means less building and electrical works are required when installing a VRF system.
Air-cooled condensing units are easily located on a roof, or on service balconies in the case of a high rise office block. Chiller units are less compact and need to be housed in a separate plant room, which has a financial impact on rentable space.
They are also high capacity compared with VRF condensers and require a more powerful standby generator to cope with their starting loading demand in the event of a power supply shutdown. This all adds to project costs, while space considerations could also make chillers an impractical solution for some new build and refurbishment installations.
Controllability is design issue
Controllability is an important design consideration and key to optimising user comfort and system performance. Air conditioning controls must suit the application in terms of size and sophistication and provide useful data for service engineers and facilities managers. VRF equipment has distinct advantages over other types of office air conditioning systems when it comes to flexibility of operation.
The cooling or heating operation of a VRF indoor unit can be controlled on an individual basis to provide a comfortable temperature in any part of a building. This option is not really available as standard with a chiller system and can only be achieved by installing a separate control system, adding extra design, installation and maintenance costs.
New developments in control software for VRF air conditioning make it possible to extract maximum performance from a system, while still leaving individual users free to select higher or lower temperatures within the allowed range.
Samsung's Data Management Server (DMS2), for example, can manage a system of up to 256 indoor units, including energy recovery ventilators and air handling units. The system manager can control single units, groups or an entire system - and through the built-in web server, full control is possible from anywhere with internet access. This flexibility of design and control means that in the event of a partial system failure, not all areas are necessarily affected, and unoccupied office areas or vacant floors can be isolated to avoid incurring unnecessary heating or cooling costs.
Fault-finding in modern VRF systems is also more sophisticated compared with other types of air conditioning solutions, with real time monitoring and immediate notification of remote failures for rapid service response. In addition, Samsung's DMS2 software can monitor energy usage by individual indoor unit. This enables electricity consumption for air conditioning to be apportioned to individual tenants, which can be a useful facility for multi-occupancy office buildings with a single efficient VRF system.
Gone are the days when function was the only consideration when designing air conditioning for an office building. Today, aesthetics can be just as important and the style and type of indoor unit plays a major role in the overall system design.
As well as their cooling/heating capacities, indoor units can be specified to complement interior décor. VRF solutions offer a wide variety of options compared with chiller based systems, making it easier to meet the design requirements of each project, and individual locations within a building.
These range from floor or wall mounted units to ceiling cassettes. Consideration must also be given to the interior layout when specifying indoor units.
Suited to a smaller office
Needless to say, the directional air-flow from a wall mounted unit makes it best suited to a smaller office, while four-way cassettes and ducted units are the most efficient option for air conditioning large, open plan office areas.
Given the design advantages of VRF type air conditioning systems, more and more commercial installations are now moving away from the big chillers. Even though the initial investment may be higher, VRF systems can deliver the comfort, control, and choice that office air conditioning demands. And, once installed, VRF technology provides greater flexibility for cost-effective zoning combined with lower running costs and reliability, creating operational savings and lower lifetime costs.