Combustion Air Requirements - Bosch 830 ES Installation And Operating Instructions Manual

Installation instructions
4.4

Combustion air requirements

CAUTION:
▶ In areas where outside temperatures routinely come close
to freezing, sealed combustion operation is required. Use a
concentric termination or separate terminations for
combustion and vent, which must be installed on the same
wall or roof surface, however never facing the direction of
prevailing winds. Failure to do so may result in heat
exchanger freezing up and bursting. This failure is not
covered under the manufacturer's warranty.
CAUTION:
▶ When installed in an environment where corrosive
chemicals or dirty air (e.g. hair salons, car washes) are
present the twin pipe system is required.
Twin pipe and Concentric pipe
The water heater is designed as a sealed combustion appliance.
It is recommended that the combustion air be provided by a
dedicated 3" or 4" pipe from the outside (twin pipe) or by
connecting to the Concentric vent kit (see Fig. 8, 9 & 10). The
combustion air pipe may be PVC or any other rigid sealed 3" or
4" pipe. The combustion air piping must pitch down 1/4 inch
per foot towards termination to prevent rain water from
entering the appliance. In twin pipe penetrations, the
combustion air inlet, whether terminating vertically or
horizontally, must be located in such a manner as to provide a
minimum 3 foot clearance from the exhaust vent termination.
See fig. 11 and 12 Letter I, page 20.
For the maximum length of the combustion air pipe, see
table 9.
CAUTION:
▶ Terminations must prevent rain and debris from entering
the combustion air and exhaust vent piping.
Single pipe
WARNING:
▶ Single pipe venting is forbidden in manufactured (mobile)
home installations.
34
Note: This appliance requires 9950 cubic feet of available
combustion air, or a minimum of 1243 square feet of space
with an 8 foot ceiling to operate. If the large amount of air
space, which equates to about half of most average sized
homes, is not available, the appliance must pull air from the
outside (see twin pipe above).
Although it is permissible to draw combustion air from inside
the structure, it is not the manufacturer's recommended
installation method. Always install a 3 inch elbow on the top of
the combustion air inlet adaptor to prevent foreign objects from
falling into the unit.
If a single pipe installation is utilized, follow guidelines below for
providing adequate combustion air for the water heater as well
as any other appliances that may consume air in the space.
Always follow local codes if they are more stringent.
This Installation Manual specifies the minimum vertical vent
pipe and the amount of combustion air required for this unit.
When all requirements are followed, the unit will operate
properly and safely. However, there may still be a risk of
freezing due to negative draft if the other combustion
appliances in the building are not supplied with sufficient
combustion air. A wood stove or furnace can pull its combustion
air from the heater's vent pipe, allowing the cold incoming air to
freeze the cold water in the heat exchanger. Supplying more
combustion air for all combustion appliances is the solution. A
HVAC specialist should be consulted to design solutions for
providing more combustion air.
Observe the following guidelines:Installations in structures that
have been tightly constructed (air infiltration rate of 0.40 ACH
or less) must be provided with combustion air per the National
Fuel Gas Code. Consult a HVAC specialist if your air infiltration
rate is questionable.The space must have two permanent
openings, one commencing within 12 inches of the top and one
commencing within 12 inches of the bottom of the enclosure.
• Appliances located in unconfined spaces:
– a) An unconfined space is one whose volume is greater
than 50 cubic feet (1.42 cubic meter) per 1000 BTU/
hr (292.81 Watts) of the combined rating of all
appliances installed in the space. That would be 9950
cubic feet (281.8 cubic meters) for the water heater
alone.
– b) In unconfined spaces in buildings of conventional
frame, masonry, or metal construction, infiltration air is
normally adequate to provide air for combustion.
• Appliances located in confined spaces:
The confined space must be provided with two permanent
openings, one commencing within 12 inches (304.8mm)
of the top and one commencing within 12 inches
830 ES – 6 720 644 936 (2021/08)