Information for installation
General information
29
most that can happen in smaller boilers in the event of
a deflagration is that the flue pipe to the chimney can
be pulled apart, in larger boilers the gas volume is
already so large that a boiler door can be blown off.
For high points before descending sections or at the
beginning of a long horizontal section (L > 20 x D), a
deflagration damper is required regardless of the boiler
output.
DANGER!
Position of the deflagration damper
Position the deflagration damper so that no people
are endangered.
7.1.2
Renovation
Chimney renovation before it's too late
Compared to older boilers, modern ones are more
efficient and have lower amounts of flue gas and con-
siderably lower temperatures.
Chimneys with a "too large diameter", in particular, can
no longer be heated adequately. The moisture
contained in the flue gas condenses in the chimney,
resulting in the very slow but inexorable destruction of
old masonry chimneys.
Furthermore, the exit velocity and temperature are too
low if the diameter of the chimney is too large. The flue
gas then lacks the energy to rise and, in extreme
cases, the smoke can sink down along the roof.
If your chimney does not have a moisture-resistant
liner or its diameter is too large, it will require
renovation in the form of a new, moisture-resistant
liner. Narrow chimneys can also be renovated by the
addition of stainless steel pipes.
Also keep in mind that chimneys have a limited service
life. Timely renovation before destruction of the
chimney wall can be achieved quickly and easily by
inserting a tube. But if the flue gas condensates have
penetrated the mortar joints, the entire chimney must
be dismantled and rebuilt.
Chimney renovation with a stainless steel pipe
Maybe the chimney has already been renovated for oil
or gas with a stainless steel pipe, and now a
conversion to wood or pellets is planned. Or the
chimney is too narrow to install a ceramic pipe with a
reliable seal. If a moisture-resistant inner pipe is
installed in a sufficiently fire-resistant casing, the
German Association of Chimney Sweeps has found
the following solution to the standards and regulations
dilemma: "in the certification of suitability and safe use
for heating systems, it should be noted that after a soot
fire the long-term durability cannot be ensured and
penetration of the chimney by moisture cannot be
ruled out so that it may be necessary to replace the
inner pipe (Criteria for Determination of Suitability and
Safe Use of Heating Systems - October 29th 2008,
page 12).
Replacing the inner pipe and seals after a soot fire
The boiler is equipped with safety routines to prevent
soot burning. Nevertheless, in very rare cases, it is
possible that a soot fire may occur in the chimney. After
that, it is very likely that the inner pipe of the chimney
and the flue pipe from the boiler to the chimney will no
longer be tight.
For safety's sake, have the chimney checked by
a specialist or chimney sweep. The inner pipe
should also be replaced and the seals in the flue pipe
from the boiler to the chimney should be replaced.
7.2
General information
Approval
All heating systems require approval. Enquire at your
building authority and ask your chimney sweep.
Antifreeze
If the building is unoccupied for longer intervals in
winter, up to 30% antifreeze can be added to the
heating water. To compensate for the disadvantage of
reduced heat capacity and increased flow resistance,
only slightly higher flow temperatures are needed.
Insulate contact sensors
If the pipe in the vicinity of a contact temperature
sensor is not insulated (e.g. in externally installed
heating circuit assemblies), lower than actual tempera-
tures will be measured. For this reason, the pipe
insulation of heating circuit flow sensors must not be
recessed or weakened. For uninsulated pipe systems,
mineral wool insulation at least 20 mm thick is required
for the measurement area over a pipe length of 20 cm
minimum.
Return riser
Wood contains water. If the temperature in the boiler is
too low, steam condenses from the flue gas onto the
heat exchanger surfaces. Corrosion and a leaky heat
exchanger are the result. To prevent this, the water
temperature at the boiler inlet must be at least 60°C.
Since the return temperatures are usually lower, a
return riser is needed to provide controlled, heated
flow to the boiler return.
