Information for installation
Chimney
27
smoke to escape into the boiler room as the boiler
heats up. The flue pipe must always be laid so that it
ascends towards the chimney.
Long horizontal flue pipes to the chimney must have a
narrow cross-section and above-average insulation (>
50 mm). Provide enough cleaning openings in the flue
pipe. A flue pipe to the chimney with a large cross
section would reduce the calculated required chimney
cross section. However, ash deposits will form at low
flow speeds, and the theoretically calculated flue
draught will be lost again.
With a large chimney cross-section, a maximum
straight length of the flue pipe up to half the effective
chimney height is possible (calculation required).
A draught limiter is required
A draught limiter must be mounted in the chimney.
Because the flue gas recirculation conveys a portion of
the flue gas back to the boiler to cool the combustion
chamber. An overly strong flue draught prevents the
recirculation to the boiler and the flue gas reaches the
chimney immediately, thus rendering the flue gas recir-
culation ineffective. This leads to slag formation and
increased wear on the boiler.
Fig. 7-1: Draught limiter
At a minimum, the draught limiter must correspond to
the diameter of the chimney and should optimally be
connected 0.5 m below the flue tube connector in the
chimney. If that is not possible, installation in the
connection pipe to the chimney is required. Example:
Chimney: dia. 300 mm
Connection pipe to chimney: dia. 250 mm
=> a draught limiter of at least 300 mm diameter is
required.
Fig. 7-2: optimum placement of the draught limiter
Connection to the sewage system for the chimney
For the condensate in the chimney, a connection to the
sewage system (e.g. duct) with at least DN25 via a
siphon is required. The sewer pipe to which the con-
densation drain pipe is connected should be flushed
once a year.
Fig. 7-3: Condensate drain
For chimneys on the outer walls (made of
stainless steel, for example), frost-proof run-off
must be provided for the condensate water.
