Viessmann vitodens Technical Manual page 128

4.2 Design and sizing information for flue pipe connections
300
Multi-boiler systems with pressurised flue gas systems (open flue operation)
Vitodens 300, 49 to 66 kW
Up to 4 gas fired condensing boilers,
49 or 66 kW, may be connected to a
common pressurised flue pipe. The max.
output is 264 kW.
The Vitodens 300 multi-boiler systems
with common pressurised flue gas
systems are provided for open flue
operation (type B).
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Installation requirements
Combustion air apertures
Gas fired equipment with a total rated
output greater than 50 kW must be
provided with combustion air apertures
leading to the outside. The cross-section
2
should be at least 150 cm , and should be
2
2 cm larger for each additional kW above
50 kW total rated output. This
cross-section may not be split over more
than 2 apertures (observe FeuVo and
TRGI '86/96 point 5.5.4 or local
regulations).
Example: Vitodens 200, 4 × 66 kW
Total rated output 264 kW
2 2
150 cm + 190 × 2 cm = 530 cm
2
2 × 265 cm .
The combustion air apertures should be
2 2
at least 530 cm or 2 × 265 cm .
Installation clearances
For a simple installation we recommend a
clearance of approx. 100 to 150 mm
between the gas fired condensing boilers.
The flue gas collector pipes can be
suitably matched.
Flue gas non-return valve
A flue gas non-return valve is installed
above each boiler, i.e. in the area of the
collector pipe.
During the boiler operation, the spherical
shut-off part of the flue gas non-return
valve is lifted by the overpressure of the
variable speed fan and thereby releases
the flue gas.
The shut-off valve closes the flue path for
all those boilers which are not in use.
Approval
The Vitodens 300 gas fired condensing
boilers, 49 and 66 kW, are tested and
certified together with their respective
flue gas system. The flue pipe has been
approved with certificate Z 7.2 1104.
Inspection aperture
FeuVo makes the installation of an
inspection aperture inside the boiler room
mandatory.
Use an inspection aperture in accordance
with the selected flue pipe diameter (for
sizing tables, see page 130).
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or
VITODENS