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. Also it can be worked with 220V. The insulation material used is of such high efficiency that the loss of heat in the fresh water is only around 12°C per 24 hours. It may be installed either horizontally or vertically. 220V, 1000W heating element.