Buderus Logamax plus GB162 Technical Manual page 135

Existing chimney shaft
Generally, a chimney sweep should clean the chimney
prior to installing a flue system with the Buderus GA-K or
ÜB-Flex set in conjunction with GA-K if one or more of the
following applies:
• The combustion air is drawn in via an existing chimney
shaft to which oil or solid fuel combustion equipment
has been connected or
• Dust loads due to unstable chimney pointing must be
expected.
If dust loads continue to be a risk factor or deposits from
oil or solid fuel combustion equipment are still present,
use the DO-S or GAL-K sets instead of the GA-K or
ÜB-Flex sets in conjunction with GA-K.
Air/flue gas system
The concentric air/flue gas line of the Buderus LAS-K set
is installed as a connection pipe between the gas
condensing boiler and the air/flue gas system (LAS). The
fan of the gas condensing boiler generates positive
pressure inside the inner pipe of the connection piece to
the LAS. Negative pressure is created in the flue shaft of
the LAS through thermal updraught.
Condensate drain from the flue
To ensure the safe drainage of condensate, the flue must
be installed with a 3° slope (5 cm/m) from the vertical
section of the flue system towards the boiler. In the case
of longer horizontal flue sections it may be necessary to
support the horizontal section on site to ensure the
correct slope towards the boiler. The condensate from the
flue and from the flue gas header in the gas condensing
boiler flows directly into the stench trap (siphon) of the
gas condensing boiler.
Drain the condensate from the moisture-resistant flue on
site when connecting to a moisture-resistant flue with the
Buderus LAS-K sets (LAS multiple connection).
Route the condensate from the gas
condensing boiler (the flue) and the
moisture-resistant flue system correctly to
the public sewer or neutralise it, if required.
Special design information regarding
condensate drainage
6 720 645 821 (2010/09) – Logamax plus GB162
chapter 7.
Flue systems for balanced flue operation
Shafts for flues
Shafts for flues must not be used for any
other purpose.
Flues that bridge several floors must be arranged in their
own shafts inside buildings.
Exceptions
• Flues in building categories 1 and 2, provided that the
flue is not routed through more than one utility unit.
Building categories 1 and 2 are those with a height to
the top edge of the floor on the highest storey that
could house an installation room of no more than 7 m
on average above ground level, and with no more than
two utility units of no more than 400 m
• Flues with a single connection inside the room where
the combustion equipment is installed or
• Flues operated with negative pressure:
– that offer a fire resistance of at least 90 minutes (ID
L90 or higher) and
– in building categories 1 and 2 that offer a fire
resistance of at least 30 minutes (ID L30 and
higher).
Several flues in a common shaft are only permissible if:
• the flues are made from non-combustible materials or
• the associated combustion equipment is installed on
the same floor or
• a transfer of fire between floors is prevented through an
automatic shut-off facility or other measures or
• the flue has received general Building Regulations
approval.
These shafts must offer:
• a fire resistance of at least 90 minutes and
• in building categories 1 and 2, a fire resistance of at
least 30 minutes.
10
2
in total or
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