Bosch 125B LPS - Manual (Page 7)

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VENTING
Vent pipe connection. WARNING: Do not reduce the vent pipe size. See Fig. 3 for high altitude installations
The heater must be vented to the outside following all local ordinances and specifications for installing a gas appliance
vent or chimney. The heater must be located as close as practicable to a vertically rising chimney or vent that has a listed
vent cap at its termination point. The venting system must be designed and constructed so as to develop a positive flow
adequate to remove flue gasses to the outdoors.
Consult the National Fuel Gas Code if the vent will have elbows or share venting with another natural draft appliance.
The heater should never be common vented with a mechanically vented appliance. Single wall vent pipe is not
recommended, if used consult the National Fuel Gas Code.
Horizontally venting to a sidewall vent terminator or a vertically constructed vent stack along an outside wall of a building
is not permissible. A Powervent (Model AQ-1), with a proof-of-draft safety interlock device, is required and is available in
order to sidewall vent. Contact your dealer. In the Commonwealth of Massachusetts: Powervented applications must
utilize proof-of-draft safety interlock device.
VERTICAL GAS VENT: A 5 inch diameter gas vent constructed of double wall Type B gas vent is recommended. 6 inch is
required in elevations greater than 2000 feet, see Fig. 3. Any gas vent section that is greater than 45 degrees from the
vertical is considered horizontal. Horizontal sections must slope upwards at least ¼ inch for every foot of its horizontal
length and be properly supported. Keep the horizontal section short and avoid too many elbows. The minimum vertical gas
vent height allowed is 6 feet; horizontal vent connectors and elbows are not to be considered in the total gas vent height.
All gas vent sections must be secured to each other with sheet metal screws and be properly supported.
The gas vent constructed of double wall Type B gas vent must terminate above the roof surface with a listed vent cap at
a height that’s in accordance with Figure A or B and their table, provided they are at least 8 feet (2.4 m) from a vertical wall
or similar obstruction. All other gas vents that are not able to terminate within the minimum specified height allowed must
terminate not less than 2 feet (0.6 m) above the highest point where it’s passed through the roof and at least 2 feet (0.6
m) higher than any vertical wall or similar obstruction within 10 feet (3.1 m).
LISTED VENT CAP
LISTED VENT CAP
LISTED GAS VENT
LOWEST DISCHARGE OPENING
H (minimum) height
from roof to lowest
discharge opening
Figure A Figure B
ROOF PITCH
IS X/12
12
X
Roof pitch H (minimum) feet meters
Flat to 6/12 1.0 0.30
6/12 to 7/12 1.25 0.38
Over 7/12 to 8/12 1.5 0.46
Over 8/12 to 9/12 2.0 0.61
Over 9/12 to 10/12 2.5 0.76
Over 10/12 to 11/12 3.25 0.99
Over 11/12 to 12/12 4.0 1.22
Over 12/12 to 14/12 5.0 1.52
Over 14/12 to 16/12 6.0 1.83
Over 16/12 to 18/12 7.0 2.13
Over 18/12 to 20/12 7.5 2.27
Over 20/12 to 21/12 8.0 2.44
GAS VENT TERMINATIONS FOR LISTED VENT CAPS