The Intergas HRE & EcoRF Boiler Range utilise a concentric flue arrangement consisting of a 60mm diameter inner flue (exhaust) and a 100mm diameter outer (air inlet) duct as standard. The system can be installed in a horizontal or vertical configuration up to a total length of 10 metres from the boiler to its termination point e.g. suitable outside wall/roof area. Should there be a requirement for bends to be installed along the length of the flue this will impact on the permitted distance that the flue can be run. Your as a Gas Safe Registered Engineer should check this prior to installation and advise on the suitability of this system.