Combustion Air Supply - Viessmann Vitocrossal 300 CU3A Installation Instructions Manual

Direct Venting (Two-pipe System)

Combustion Air Supply

The Vitocrossal 300 CU3A boiler is suitable for vertical
venting using rigid pipe and flexible pipe vent system
material. The Vitocrossal 300 CU3A boilers are approved
for both direct vent (sealed combustion), as well as direct
exhaust (non-sealed combustion) operation in vertical
arrangements. For non-sealed combustion vent systems
(i.e. room-air dependent), see appropriate section under
"Single Pipe Venting" starting on page 70 in this manual.
The boiler must be connected to a direct vent system
in which all air for combustion is taken from the outside
atmosphere and all combustion products are discharged
safely to the outdoors.
The boiler must be vented and supplied with combustion
air and exhaust vent as described in this section. Ensure
the vent and combustion air supply comply with these
instructions.
CAUTION
Do not locate boiler in areas where high dust levels or
high humidity levels are present.
CAUTION
Do not install boiler during construction involving drywall
or heavy dust of any kind. Dust can accumulate in the
burners and cause sooting. Install boiler after all heavy
dust construction is completed.
* Typically when the boiler is used as a temporary heat
source during the building construction phase.
62
CU3A Venting Systems Installation
Inspect all finished exhaust vent/air intake piping to ensure:
Vent/air intake pipe and fittings are of approved material.

Acceptable size, length and number of elbows on

combined vent/air intake system.
Installation is in accordance with prevailing provisions

of local codes.
Installation complies with the requirements of these

instructions, as well as the exhaust vent/air intake
supplier's instructions.
The exhaust vent and combustion air intake system and
terminations may be installed in one of the following type
terminations (2-pipe system):
1. Vertical air intake and exhaust vent pipes.
2. Horizontal air intake pipe and vertical exhaust vent pipe.
CAUTION
If the boiler has been exposed to high dust levels, all
burners and the heat exchanger must be cleaned prior
to use.
CAUTION
If above criteria are not properly observed and boiler
damage results, any warranty on the complete boiler
and related components will be null and void.