Mitsubishi Electric moves to the next stage of water-cooled VRF air conditioning
Mitsubishi Electric’s second generation of water-cooled VRF air conditioning in the UK uses R410A as the refrigerant.
Mitsubishi Electric’s water-cooled City Multi VRF air-conditioning, first launched in 2000 using R407C refrigerant, is now available with R410A. New features, combined with water cooling, enable extremely energy-efficient installations to be achieved. A VRF circuit of up to 16 indoor units can be linked to one condensing unit. The energy efficiency of the circuit can be optimised by heat recovery within that circuit, transferring energy from areas that require cooling to those that require heating — and vice-versa. The condensing units are connected to a water loop, and energy can be transferred between VRF circuits. Imbalances of energy among VRF circuits connected to the water loop can be dealt with using a range of heat-input and heat-rejection technologies. As well as boiler plant, cooling towers and air-cooled condensers, solar power and ground-water sources can be engineered into a project. Efficiency comparisons for the new system over 2001 technology show a 250% improvement at UK cooling conditions and a 77% improvement at UK heating conditions. Philip Ord, product marketing manager for the City Multi range of air conditioning, explains, ‘The innovative thing about WR2 is that the condensing units are able to recovery surplus heat from a variety of sources and transfer it to where it is needed using our unique 2-pipe system.’ Water-cooling also brings a range of installation benefits. Water-cooled condensing units are smaller than their air-cooled counterparts so that they can be sited in indoor plant rooms close to the circuits they serve. Once the water loop for a building has been installed, VRF circuits can be added as required, making possible phased installation. Mitsubishi Electric has completed a range of water-cooled projects in the UK. They include Boots in Canary Wharf and GAP in Kingston upon Thames, where the WR2 systems link into the existing condensing water loops. An example of a shopping centre is the Dundrum Shopping Centre in Ireland, which has multiple shops using WR2 to provide total heat recovery. At the Hotel Zetter in the Clerkenwell area of London, a WR2 system is linked to an underground reservoir through a borehole. For this project, the small space requirements of water-cooled condensers over air-cooled enabled more accommodation to be provided — increasing the hotel’s earning capacity. ‘A WR2 system linked to a borehole will cost just under double the cost of a 10 HP City Multi air-cooling condensing unit, but the system delivers a reduction in running costs of 43%,’ says Philip Ord. The new WR2 range includes 8, 10, 16 and 20 hp units. They are inverter driven and deliver COPs from 3.5 to 7 by offering the potential for single or double heat recovery over pipe runs of up to 400 m. They are said to offer a replacement or alternative for traditional chilled-water air conditioning.