It  represents a modern concept of "D" shaped desing, having two overmounted drums, expanded vertical tubes and full water walls type furnace. The water circulation inside the boiler is of the natural type. Flue gas tightness is realised on the external walls by means of longitudinally finned tubes.
External walls and drums are insulated by means of high density rock wool panels, covered by stainless steel lagging, water tight for outdoor installation, anchored to the supporting structure and easy to disassemble.