Ariston CLAS HE R Installation And Servicing Instructions page 21

For coaxial systems, the maximum development value, mentioned
in the table below also takes into account an elbow.
For twin flue systems the maximum development value, mentioned
in the table includes the exhaust gas/air intake terminal.
Twin flue systems outlets should respect the following instructions:
1- Use the same ø 80 mm flue pipes for the air intakes and exhaust
gas ducts.
2- If you need to insert elbows in the air intake and exhaust gas
ducts, you should consider for each one the equivalent length to
be included in the calculation of developed length.
3- The exhaust gas duct should jut above the roof by at least 0.5 m.
4- The intake and exhaust gas ducts in Type C13 + C53 must be
installed on the same wall, or where the exhaust is vertical and
the air intake horizontal, the terminals must be on the same side
of the building.
120
INSTALLATION
180
AIR INTAKE MUST NOT BE
FITTED ABOVE THE EXHAUST
AIR INTAKE EXHAUST
Fig. 10
AIR INTAKE
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Fig. 9