Double-walled calorifier. The engine coolant is circulated between the inner and outer jacket of the Vetus calorifier, which heats up the fresh water inside the inner boiler. The insulation material used is of such high efficiency that the loss of heat in the fresh water is only around 12 deg celsius per 24 hours. Vetus calorifiers may be installed either horizontally or vertically. A connection set and a 1000W electric heating element are supplied as standard.