6
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Termination Heights for Vents
Above flat Or Sloped Roofs
Ref. NfPA 54 / ANSI z223.1
Roof Pitch
* feet
* Meters
Flat to 6/12
1.0
0.3
6/12 to 7/12
1.25
0.38
7/12 to 8/12
1.5
0.46
8/12 to 9/12
2.0
0.61
9/12 to 10/12
2.5
0.76
10/12 to 11/12
3.25
0.99
11/12 to 12/12
4.0
1.22
12/12 to 14/12
5.0
1.52
14/12 to 16/12
6.0
1.83
16/12 to 18/12
7.0
2.13
18/12 to 20/12
7.5
2.29
20/12 to 21/12
8.0
2.44
VENT TERMINATION
CLEARANCES
Multiple Terminations
These appliances may vent adjacent to and at
the same level with any other gas appliances
(including direct vent appliances), provided
there is at least 2 ft (0.6 m) between the proxi-
mal edges of the vent caps. These appliances
may be vented adjacent to a chimney vent
servicing a solid fuel fireplace, provided the
B-vent cap is at least 2 ft (0.6 m) away from the
nearest point of the chimney opening.
Gas Vent Rule
Gas vent caps are not permitted within 8 ft (2.4
m) of a vertical wall or similar obstruction. Gas
vent caps that are located 8 ft or more from a
portion of a building that extends at an angle
greater than 45° upward from the horizontal
may terminate in accordance with Figure 4,
provided that any discharge opening on
the cap is NEVER LESS THAN 2 ft (0.6 m)
horizontally from the roof surface
(National
Fuel Gas Code ANSI Z223.1 (NFPA 54) “Gas
Vent Termination” section) (CAN/CGA B149.1).
Figure 4
Roof Pitch is X/12
Minimum Height from Roof to
Lowest discharge Opening
X
12
1" (25 mm)
Minimum
Gas Vent Rule
Table 5
LENNOX HEARTH PRODUCTS • MERIT
®
SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS
