Continuously operated hot water systems
CONTINUOUSLY CIRCULATED HOT WATER SYSTEMS (known as recirculating, secondary hot circulation, return or ring main systems) carry pumped hot potable water to outlets where the temperature is between 60oC to 70oC and is replenished by an incoming water supply to replace the water drawn to outlets. These systems are very different from intermittent systems for hot water distribution which are only hot when water is being drawn. Only products approved by the manufacturer for continuously operating systems should be used. The manufacturer and their technical information must always be consulted for specific limitations. For more information see Annex A of the Guidance Note - Hot and Cold Water Supply and Central Heating.
Domestic Hot and Cold Water Supply and Central Heating Systems Guidance Notes