Connections
22
Venting Connection (continued)
Riser box
If unable to f ind sufficient clearance
above grade at the point where the vent
passes through the outside wall, a vent
riser box may be used.
If a vent riser box is being considered,
remember to include the equivalent
lengths of two elbows (6 ft. / 1.83 m)
plus the height of the riser in the vent
length calculations. Do not exceed the
total equivalent length of 20 ft. / 6 m.
Also, the te rmination tee must be
ordered.
Theventpipeenclosedintheriserbox
must be insulated to resist condensate
freeze-up. The riser box must be sealed
to prevent moisture entering and
soaking insulation. If the ex t erior wall
finish is a combustible material, the
vent riser box should be constructed to
provide sufficient clearance to
combustibles.
For boilers connected to large water
content systems, such as a previous
gravity system with large free-standing
column type radiators, a bypass line
from supply pipe to the return pipe can
be used. A minimum return water
temperature of 120°F can be achieved
by diverting some of the flow of heated
supply water into the f low of return
water to the boiler. V alves suitable for
balancing, such as globe v alves, s hall
be used and a thermometer installed in
the return line.
The Vitogas 050, ECV boiler is also
approved for Flex-L Star-34 vent. If
using this vent model, please contact
Viessmann for the corresponding
installation instructions.
For boilers connected to underfloor
heating systems utilizing plastic tubing
with an oxygen diffusion barrier, a
4-way mixing valv e with ex ternal
control or other suitable alternative
must be installed to prevent
condensation and keep boiler return
water a minimum of 120°F.
Manufacturer can be contacted to help
resolve doubts and technical aspects of
boiler installation.
5167 450 v1.4
Condensation can occur in the heat
exchanger if boiler is operated for
long periods of time with low return
water temperatures (e.g. 120°F or
less). Significant condensation in the
boiler will cause corrosion and
premature failure. This type of failure
is not covered under warranty.
CAUTION
The induced draft blower cannot
compensate for inadequate
combustion air. The blower is for the
venting system only. Failure to
provide adequate fresh combustion
air can cause property damage,
severe personal injury, or los s of life.
WARNING
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