Combustion Air Requirements; Proper Location For Installing Your Heater; Heater Placement And Clearances; Mounting Installation - Bosch 520PN Applications 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 15.
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 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 the 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 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 (304.8mm) of the bottom of the
enclosure. Each opening must have a minimum free area of one
square inch per:
C 1210 ES/ESC
– 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:
▶ 1. Locate the heater where venting, gas and plumbing connections
are feasible and convenient.
▶ 2. The hot water lines should be kept short and insulated to save
energy. Centrally locating the water heater is recommended to keep
hot water distribution times even throughout the structure.
WARNING:
▶ The water in this water heater is cold and always
remains cold except for the times the burner is on. In
the event of power outage in conjunction with
freezing temperatures, it is recommended that the
heater be drained.
See chapter 7.2, page 36 "Winterizing" for draining
instructions.
WARNING:
▶ Flammable materials, gasoline, pressurized
containers, or any other items or articles that are
potential fire hazards must NOT be placed on or
adjacent to the heater. The appliance area must be
kept free of all combustible materials, gasoline and
other flammable vapors and liquids.
4.6

Heater placement and clearances

The water heater design is approved for installation on a combustible
wall (see chapter 4.7 Mounting installation) provided the floor covering
below the heater is noncombustible.
For installations in an alcove or closet, maintain the minimum clearances
to combustible and non-combustible materials. See fig. 6, page 10.
4.7

Mounting installation

WARNING:
before mounting appliance:
▶ Check that there are no loose or damaged parts inside
the appliance.
▶ Confirm that the gas type of the heater matches the
gas supply you will be connecting the heater, See
Fig.2, page 8.
Installation instructions | 23
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