What is the maximum horizontal flue length for the I 24 boiler?

The total maximum permissible horizontal concentric flue length for the 24 kW appliance is 9 metres, minus any flue kit options or bends. This is measured from the centreline of the turret to the outside of the wall terminal. A 90° elbow has an equivalent flue length resistance of 1 metre, and a 45° elbow has a resistance of 0.6 metres. (Page 19)