Applications manual
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15
GB125 Concentric Vent
Design Manual
GB125 Concentric Vent Design Manual | 05.2009
Technical specifications are subject to change without prior notice
9.
Chimney Liner – GAK Venting System
kit
Use the GAK kit for installations with an existing masonry
chimney in good condition. It consists of concentric
DN80/125 pipe-in-pipe from the boiler to the chimney, and
inside the chimney chase a sealed DN80 plastic flue gas
pipe runs up to the termination at the top. The space
surrounding the flue gas pipe is used to draw combustion
air from the roof to the boiler.
The GAK System ensures a sealed combustion system
from the boiler to the termination.
The GAK system draws combustion air from the
roof and may not be suitable for installations with
multi-flue chimneys, where a second flue vents a
combustion appliance that is used on a regular
basis. Flue gases could be drawn in with GB125
combustion air and cause service calls.
For installations in multi-flue chimneys with a risk of
ambers from wood stoves or similar appliances
reaching the top of the chimney, optional stainless
steel terminations are available. See list of
accessories (Tables 8-10).
Minimum chimney chase dimensions to ensure sufficient
supply of combustion air:
Rectangular:
5” x 5” (120 mm × 120 mm)
Round:
DIA 5-1/2” (Ø 130 mm);
If the chimney is not a straight run but has an offset or
bend, you can still use the rigid pipe as long as the
bottleneck is accessible for the installation of elbows. If
inaccessible, use the GAK system with the UB Flex pipe
(Page 21) instead.
CAUTION! Never connect this concentric vent to a
common venting system
The chimney flue must not be used with any other
appliance or for any other purpose, must be in good
condition, and must be thoroughly cleaned before
conversion to GAK.
You will need to purchase the basic kit GAK (DN125/80) in
any case. For the content see Table 7 and Fig. 9. Select
additional items and accessories from Tables 8-10 as
needed.
Fig. 9 GAK basic kit
