Double wall chimney system DW25

Double wall chimney system is designed to exhaust combustion products from heating appliances by natural draught and can be installed inside or outside the house.

Chimney system for particular cases must be selected according to the documentation of the heating appliance manufacturer, chimney installation guide and national legal acts.


Oil, gas, solid fuels

Working temperature

≤ 200 °C
≤ 450 °C
≤ 600 °C


Inner pipe: stainless steel EN 1.4404
Outer pipe: stainless steel EN 1.4301 or painted steel

Wall thickness

When dn from 80 to 200 mm – 0,5, 0,6, 0,8, 1,0 mm
When dnfrom 230 to 550 mm – 0,6, 0,8, 1,0 mm

Pressure class

N1 – natural draught
P1 – positive pressure (with gaskets)


Injected mineral wool, thickness – 25 mm

Sootfire resistance

G – resistant
O – not resistant (with gaskets)

Distance to combustible materials

≥ 1001 mm (designation 1)
≥ 501 mm (designation 1a)
≥ 1001 mm (designation 2)
≥ 501 mm (designation 3)

Condensate resistance

W – designed for wet operating conditions



System marking

EN 1856-1 T600-N1-W-Vm-L50XXX-G100 (1)
EN 1856-1 T600-N1-W-Vm-L50XXX-G50 (1a)
EN 1856-1 T450-N1-W-Vm-L50XXX-G100 (2)
EN 1856-1 T200-P1-W-Vm-L50XXX-O50 (3)


1 The minimum distance to combustible materials from the outer pipe of a chimney must be selected according to the technical specifications of the chimney, as described in their marking and national legal acts. If the legal acts and chimney technical specifications indicate different admissible distances of the combustible materials, it is necessary to select the higher distance. The minimal distance to combustible materials were determined using 200 mm diameter chimneys. The distance to combustible materials for chimneys larger than tested must be increased by a factor. For dn 201-300 mm the factor must be 1 time the distance to combustible material determined for dn 200 mm, for dn 301-450 mm – 1,5, dn 451-600 mm – 2, above dn 601 mm – 4.

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