Bosch 520-HN-N User Instructions page 8

Installation instructions
Masonry chimney
Masonry chimneys shall be built and installed in
accordance with NFPS 211 or local codes. A minimum
5" diameter gas vent pipe (metal double wall Type B),
or an approved clay flue liner or a listed chimney lining
system must be used when venting into a naturally
drafting, internal masonry chimney. 6 inch is required in
elevations greater than 2000 feet, see Fig. 6. Local
codes may require the use of both gas vent and an
approved lining system when venting into a masonry
chimney. The Commonwealth of Massachusetts
requires the use of a listed liner. Lining systems include
approved clay flue lining, a listed chimney lining system
or other approved material that will resist corrosion,
erosion, softening, or cracking from exhaust flue gases
at temperatures up to 1800 degrees F. The lining
system must be listed for use with naturally drafting,
draft hood equipped gas appliances. Follow local
codes and refer to NFGC 54 and NFPA 58.
Existing interior masonry chimney
The metal gas vent pipe should be permanently
mounted inside the masonry chimney. Double wall Type
B gas vent is recommended. The masonry chimney may
have to be tile or metal lined before the insertion of the
gas vent pipe; check local codes for clarification. The
lining material must be listed for use only with naturally
drafting, draft hood equipped gas appliances. Follow
manufacturer's instructions for installation of listed
lining material. You may not vent any other fuel burning
appliances into any free space remaining in the
chimney. The minimum vertical gas vent length within
the masonry chimney must be no less than 5 ft (1.5 m);
the vent terminator must extend at least 3 feet (0.9 m)
above where the chimney meets the roofline and at least
2 feet (0.6 m) higher than any vertical wall or similar
obstruction within 10 feet (3.1 m). The top of the gas
vent must have an approved vent terminator. See Fig. 8.
LOWEST DISCHARGE
OPENING
H (minimum) height
from roof to lowest
discharge opening
LISTED GAS VENT
ESTABLISH A ONE
FOOT RISE BEFORE
ANY ELBOWS
Fig. 7 Pitch roof
8
APPROVED VENT CAP
X
12
ROOF
MINIMUM 6
PITCH IS
X/12 FEET (1.8M)
GAS VENT TERMINATIONS FOR LISTED VENT CAPS
Roof pitch H (minimum) feet
Flat to 6/12
6/12 to 7/12
Over 7/12 to 8/12
Over 8/12 to 9/12
Over 9/12 to 10/12
Over 10/12 to 11/12
Over 11/12 to 12/12
Over 12/12 to 14/12
Over 14/12 to 16/12
Over 16/12 to 18/12
Over 18/12 to 20/12
Over 20/12 to 21/12
Table 2
GAS
VENT
VENT
CONNECTOR
Establish a
one foot
rise before
any elbows
Fig. 8 Masonry chimney
meters
1.0 0.30
1.25 0.38
1.5 0.46
2.0 0.61
2.5 0.76
3.25 0.99
4.0 1.22
5.0 1.52
6.0 1.83
7.0 2.13
7.5 2.27
8.0 2.44
APPROVED
VENT CAP
6720608032-14. 1 Av
6 720 644 942