Book - School of Science and Technology

596 Hot water supply systemsInsulationHeat losses from all the components of a hot water system continue throughout the year,often day and night. To suggest that, for many systems, as much energy is dissipated inthis way as is used to heat the water drawn off at taps is no exaggeration. In consequence,a very good standard of thermal insulation to pipework is recommended. Storage vesselsfor domestic use may be factory insulated with 50 mm sprayed urethane foam or fittedwith a standard 80 mm thick quilted jacket. Larger size vessels for the commercial sectorshould be insulated to at least as good a standard, and be finished with a protective sheetmetal casing.In addition to the energy wastage taking place, the heat given off by pipes is objectionablein summer. Where such pipes are routed in ducts alongside a cold water distributionsystem, the heat added to the latter will not only make it unpalatable for drinkingpurposes but might create the very temperature in which L. pneumophilia will thrive.Solar collectorsThe most common application for solar water heatingis to provide domestic hot water.Heatingfor domestic swimmingpools also makes use of solar water heatingalthoughEdge sealGlass cover (single or double)Air spaceCollector withwater channelsOuter casing(a)Rear insulationabout 100mm thick(b)(c)Common headerCopper pipe & fin collector plateEvacuated tube(d) Typical evacuated tube collectorFigure 20.28 Basic types of solar collectors