Book - School of Science and Technology

Heat pumps 561their simplicity, proven record in use and requirement for no more than the very low levelof maintenance skills currently available, at little better than `Leggo' level.Packaged heat pumpsThese are available in a range from small domestic scale units (3 kW) through to equipmenthaving an output in excess of 4 MW heating and 3 MW cooling. At the domesticlevel, the seasonal COP of an air-source device of around 2.6, coupled with relatively highinstallation costs and poor reliability, is not an attractive alternative to conventionaldomestic heating methods for the householder. Equipment is available in a number ofconfigurations, some of the more common types of electrically driven machines beingillustrated in Figure 19.25.On a commercial scale, there is a good case for heat pumps in certain applications, suchas in swimming pools retail stores and industrial drying, where their installation is nowcommonplace. In swimming pools the heat pump is used as a heat recovery device,dehumidifying and cooling the warm and moist extract air as the energy source to heatincoming air (during cold weather), pool water and hot water supplies.Outside air fanInside air coilConditionedair fanFilterOutsideair coilCompressorCondensate tray(a) Self contained unitOutdoor unitOutside air coilOutsideair fanRefrigerant PipesAirhandlingunitCompressorConditionedair fanInside air coilCondensate trayFilter(b) Split systemFigure 19.25 Configuration of electrically driven heat pumps