Traditional catering urns are portable and simple to install and are often used in offices, canteens etc. to supply larger quantities of hot water for tea, coffee etc. They are not expensive but have to be manually filled with cold water.
In contrast to autofill boiling water units (which pre-heat incoming cold water to maintain an uninterrupted supply of boiling water) adding cold water to a catering urn will lower the water temperature until is has been reheated. Electric catering urns are rated at 3kW or less and so can be plugged into a standard 13A electric ring main wall socket. Gas versions are also available for providing catering facilities in situations where electricity is not available, such as camping, scouting, village fetes or other outdoor events. Popular catering urn brands include Swan and Burco. There are a number of options for temperature control as summarised below:
Element is switched as required to maintain water temperature at the desired level selected by the thermostat dial
Element heating power is variable and determined by the Simmerstat dial setting.
High power element takes water to boiling point. A second low power element keeps the water hot without excessive steam.
A thermostat switches the heating element off when boiling point is attained. Similar to a standard kettle.