Page.9
The concentric duct system consists of the following components: ( see page 19 )
A. Concentric pipe. K. Flat roof flashing aluminium
B. Concentric 45° bend. L. Storm collar / rosette
C. Wall bracket. M. Horizontal terminal eccentric
D. Not available N. Lead slope roof flashing 20°- 45°
E. Concentric 90° bend. O. Vertical terminal
F. Wall band adjustable. P. Slope roof flashing 5°- 30°
G. Adjustable length.
H. Flat roof plate.
I. Locking band
J. Adjustable roof plate
Connection options for concentric duct system
· Indirect wall feed-through (See Page 14 Diag. 8 & 9 ).
Always place a length of X=1 metre vertically onto the appliance, immediately followed by a 90° bend and
an external horizontal terminal set of Y (min.) length. If required, the horizontal section can be extended to
2 metres plus horizontal terminal (Y max.). See diag. 9.
· Roof feed-through without slope ( see Page 16 diag. 10 ).
A direct route without slopes is possible, up to a maximum length of X=12 metres (excluding vertical ter-
minal), measured from the connection to the fire. The minimum length is 2 metres. The outlet may occupy
any position on the roof surface (either flat or sloping); the flue and combustion air inlet are located in the
same pressure area. A restriction sheet iron ( See Page 14 diag. 7 ) must be fitted for lengths of 3 metres
and longer for all types of gas.
· Roof feed-through with 45° slope ( see Page 16 diag. 11 ).
Always fit a length of X=1 metre vertically onto the appliance. After this, the route can be continued with
two 45° bends (effective length per bend, 1 metre), until the maximum pipe length of 12 metres is reached
(including bends, but excluding vertical terminal). The minimum length is 3 metres. The outlet may oc-
cupy any position on the roof surface (either flat or sloping); the flue and combustion air inlet are located
in the same pressure area. A restriction sheet iron ( See Page 14 diag. 7 ) must be fitted for lengths of 3
metres and longer for all types of gas.
· Roof feed-through with 90° slope ( see Page 16 fig. 12 ).
Always fit a length of X=1 metre vertically onto the appliance. After this, the route can be continued with
two 90° bends (effective length per bend, 2 metres), until the maximum pipe length of 12 metres is
reached (including bends, but excluding vertical terminal). The minimum length is 5 metres. The outlet
may occupy any position on the roof surface (either flat or sloping); the flue and combustion air inlet are
located in the same pressure area. Take account of the fact that the horizontal section of pipe must not ex-
ceed Y=2 metres (measured between bends) and also ensure there is sufficient slope. A restriction sheet
iron ( See Page 14 diag. 7 ) must be fitted for lengths of 3 metres and longer for all types of gas.
Structure of concentric duct system
Installation of indirect horizontal feed-through
· The outlet can also be constructed in the outer wall in a situation with upwards discharge (always 1 metre
vertical first). Possible nuisance to the neighbourhood must be taken into account. The Buildings Decree
contains the relevant regulations. In addition, ensure that the wind pressure on the outlet is not excessive
(e.g. in extremely narrow alleyways), since this can affect the performance of the fire.
