Colin Goode, Product Manager at Fujitsu, examines some of the options available for heating and cooling a larger open plan office space for the lowest cost.
As is often the case, there is more than one way to solve a problem. For the retail and light commercial sector, the majority of projects will require the most cost-effective cooling and heating solutions available to make them viable.
- A single large capacity Ducted split system could be an option, with sheet metal ductwork above the ceiling to ceiling grilles or perhaps a fabric sock system below the ceiling. This would be a good option but not always the most cost effective due to the additional materials and installation time and labour required.
- 2 off 10 or 12kW 1:1 Cassette split systems group controlled to operate as a single system. A good option, especially if the space might be partitioned in the future meaning two zones of control might be needed.
- A VRF system with multiple indoor units is another option. A valid choice if other areas of the building are to be included as well, but not the cheapest solution for a single space.
- A Twin split system consisting of 2 x 10kW or 12kW ceiling cassettes on a single 22kW outdoor unit and a single room controller. A Triple or Quad indoor unit arrangement might also be an option for more irregular shaped rooms.
From the choices listed here, by far the most popular and most cost-effective option is number 4, the Twin, Triple, Quad, or what we call the Simultaneous Multi system. Multi system because it uses multiple indoor units and Simultaneous because all the indoor units operate together as one from a single controller and single outdoor unit. An efficient, relatively simple and easy to install solution.
Individual control of each indoor unit is not possible with Simultaneous Multi systems, nor is it needed for most open plan spaces. The capacity of the outdoor unit is shared equally across the two, three or four indoor units in a master/slave arrangement. By far the most common variant of this system is the Twin Cassette, since this uses the fewest number of indoor units and costs the least to install. Cassettes are compatible with suspended ceiling depths found in most commercial buildings and, when positioned correctly, deliver airflow equally to all areas of a rectangular space. In fact, indoor units are often used in buildings without ceilings where fully exposed cassettes are suspended on long drop rods from roof rafters.
The larger side discharge fan 19kW and 22kW outdoor units can be installed in ventilated plantrooms and ducted externally. A maximum of 30Pa duct resistance is possible. This is an extremely useful feature in built-up urban environments where outside space is limited or location of outdoor equipment is restricted.
Fujitsu now offers an extended range of Simultaneous Multi systems with capacities from 10 to 22kW that are compatible with compact/full size cassettes, floor/ceiling and ducted indoor units.
Simultaneous Multi or Twin/Triple/Quad systems are hugely popular in the light commercial sector because they are the most cost-effective solution and are scalable for spaces that require capacities of 10kW and larger. For example, up to 16 indoor units can be connected to 8 x 22kW outdoor units (as twins) and can be controlled from a single wired remote controller for a total space capacity of 176kW. This would be enough capacity for a space with a floor area approaching 1,500m2 and, if required, could provide future partitioning flexibility for up to eight separate control zones by simply adding seven extra controllers and some minor control wiring changes.
As with all systems there are limitations that apply to pipe lengths. These systems, like all other Fujitsu models, can be selected with our free-to-download Design Simulator software. The software can model the proposed pipe lengths, the refrigerant charge can be checked, indoor unit capacities calculated automatically, specifications, pipe-work and wiring schematics generated. For the larger 19 & 22kWsystems the maximum pipe length is 100m and 75m for the 10-14kW models.
So, next time you have a larger open plan office or retail space, consider using a Simultaneous Multi system.