Combustion Air Requirements; Proper Location For Installing Your Heater - Bosch Therm C 1210 ES Installation And Operating Instructions Manual

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). 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. 9 and 10 Letter I, page 20.
For the maximum length of the combustion air pipe, see
Tables 8 & 9.
CAUTION:
▶ Terminations must prevent rain and debris from entering
the combustion air and exhaust vent piping.
Single pipe
Note: This appliance requires 11250 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 the
C 1210ES/ESC – 6 720 644 887 (2022/04)
inside, it is not the manufacturer's recommended installation
method. Always install a 3 inch 90° 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 same
space. Always follow local codes if they are more stringent and
regulations.
• 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
per hour (292.81 Watts) of the combined rating of all
appliances installed in the space. That would be 11250
cubic feet (319 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
(304.8mm) of the bottom of the enclosure. Each opening
must have a minimum free area of one square inch per:
– 1000 BTU/hr (292.81 Watts) if all air is taken from
inside the building
– 2000 BTU/hr (585.62 Watts) if all air is taken from the
outside by horizontal ducts
– 4000 BTU/hr (1171.24 Watts) if all air is taken from
the outside by direct openings or vertical ducts
Or the confined space must be provided with one permanent
opening or duct that is within 12 inches (304.8mm) of the
ceiling of the enclosure. This opening must have a minimum
free area of one square inch per:
– 3000 BTU/hr (878.43 Watts) if all air is taken from the
outside by a direct opening or vertical duct.
Louvers, grills and screens have a blocking effect, when used,
increase the sizes of your openings by 300% for wood louvers
(as wood type will reduce the free air by 75%) and 43% for
metal louvers (as metal will reduce the free air by 30%). Refer
to the National Fuel Gas Code for complete information. In
buildings of tight construction all air should be taken from
outside.
4.5

Proper location for installing your heater

Carefully select the location of the water heater. For your safety
and for proper heater operation, you must provide combustion
air to the heater and a proper exhaust vent system.
Follow the guidelines below:
Installation instructions
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