Installation guide

General Information
11
General Installation Information (continued)
Recommended venting practice
When installing a venting system the
following recommended venting
practices apply:
H Keep length and number of 90º
elbows to a minimum.
H Try not to use back-to-back 90º
elbows.
H Use 45º elbows where possible to
minimize the number of 90º elbows
in case redirection of flue gas is
required.
H The special vent system shall not be
routed into, through, or within any
other vent such as an existing
masonry or factory-built chimney.
Exception:
A masonry chimney flue may be used
to route the venting system only if no
other appliance is vented in t he same
flue.
Leak test (for coaxial venting systems only)
Viessmann recommends that the
heating contractor perform a simplified
leak test during boiler start-up. For this
purpose it is sufficient to measure the
CO
2
concentration of the combustion
air in the annular gap of the air intake
pipe. The vent pipe is considered
sufficiently leak-proof if a CO
2
concentration in the combustion air no
higher than 0.2% or an
O
2
concentration no lower than 20.6%
is measured relative to a starting O
2
concentration of 20.9%.
If higher CO
2
values or lower O
2
values
are measured, inspect the venting
system thoroughly.
Continuous short cycling of the boiler
can indicate a leaking venting system.
Note that the vent pipe adaptor comes
with two measurement ports, one for
combustion air intake measurement
and one for flue gas measurement.
5368 815 v2.0 b