Air-conditioning systems

It's a facilities manager's dream: an office where everybody has individual control over the environment immediately surrounding his or her workspace.

A new type of air-conditioning system called Ecoflair claims to do just that by giving individuals direct control over both the air temperature and its velocity around their desk.

The system is based on small, individual underfloor (or in the ceiling) fan coil units called Unitiles, which are located next to each workstation. The Unitile units are sized 600 x 600 mm so that they can fit into the space taken by a single floor-tile, which means they can easily be lifted and moved to any place in the floor grid if the office layout changes.

The fan coils have flexible connections to two pipe loops positioned around the room's perimeter: one hot loop (31-35 ºC) and one cold loop (13-17 ºC). These are not simply circulation systems, they're also reservoirs of heat and cooling. Each is able to meet the full cooling or heating load of the room.

Return to sender

A "flip-flop" connector allows the fan coil to draw from either the heating or cooling loop, depending on demand. In heating mode, the fan coil draws water from the hot loop and returns it back into the same hot loop. And when cooling is needed, water is drawn from - and returned to - the cold loop.

A small pump in the flip-flop connector overcomes the resistance of the flexible connections. The number of components is small, with only one pump, only one heat/ cooling coil in the fan coil and only two connecting pipes to the unit.

The system allows each fan coil to control the micro-climate around each occupant. Air is discharged at low speed and at a temperature (19-20 ºC in cooling mode; 27-28 ºC in heating mode), to ensure personal comfort. Both air speed and temperature can be adjusted by the occupant.

Each fan coil can deliver approximately 1 kW of cooling and 1.3 kW of heating, depending on the fan speed and the water temperature in the heating and cooling loops. Air returns to the fan coil via a separate floor grille. The manufacturers claim that the floor is not pressurised using this system, so its airtightness is not an issue.

With Ecoflair, large volumes of fresh air can be introduced directly into the open floor void, via local heat recovery ventilation units with humidity control, which can mix with the return air to the fan coils.

Where this system differs significantly from other underfloor heating/cooling type systems is that it uses a local heat pump, called a Heat Transfer Unit (HTU), to maintain the temperatures in both the heating and cooling circuits. In operation, as the cold loop becomes warmer and the hot loop becomes cooler, the heat pump takes heat from the cold loop and transfers it to the heating loop.

As it is unidirectional, it is inherently more reliable than a reverse cycle machine. The HTU is also low noise. Its compressor is located within a sealed housing, entirely separate from the air delivery system, and can be located remotely from the occupant - either beneath the floor, above the ceiling or in a separate cupboard.

The manufacturers claim the unit operates at a coefficient of performance of 5.0-6.0, depending on pipe loop temperatures, because the HTU balances the cold and hot loops without calling on the central cooling or boiler plant. Only when there is no more trade-off to be made within an office, between offices, or even between floors does the system call for the external plant to take care of the imbalance.

External Plant

A multi-function, air-cooled, external packaged unit, known as an energy provider (EP) is connected to both the cold and hot loops. This module provides cooling in summer, heating in winter and a mixture of both if the heat transfer units are not able to fully balance out the loads by themselves. It comes in a number of sizes, from 100-500kW capacity, and includes a free-cooling option.

The Ecoflair system is also available in a ground-coupled version. Because it uses water temperatures close to normal ground source temperatures, it is claimed to be compatible with ground water-based solutions. Here, instead of an air-cooled chiller, the system is linked via a water-cooled version of the Energy Provider, which uses ground water as both a heat sink and source depending on conditions.

Just wait until those facilities managers hear about this.

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