6
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT PLUS
®
DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
12
X
Roof Pitch is X/12
2 FT
MIN.
2 FT MIN.
Lowest
Discharge
Opening
H*
*H = MINIMUM HEIGHT FROM ROOF TO
LOWEST DISCHARGE OPENING OF VENT
TERMINATION HEIGHTS FOR VENTS ABOVE
FLAT OR SLOPED ROOFS
Horizontal Overhang
Vertical
Wall
Vent
Termination
Storm Collar
Concentric
Vent Pipe
Flashing
1 inch (25.4 mm) Minimum
Clearance to Combustibles
Figure 5: Termination Heights for Vents
Above Flat or Sloped Roofs
Vertical Vent Termination Clearances
VENT TERMINATION CLEARANCES
These instructions should be used as a
guideline and do not supersede local
codes in any way. Install venting according
to local codes, these instructions,
the current National Fuel Gas Code
(ANSI-Z223.1-2009) in the USA or the
current standards of CAN/CSA-B149.1 in
Canada.
Vertical Vent Termination Clearances
Terminate multiple vent terminations
according to the installation codes listed
above and Figures 4 and 5.
Note: See Figure 34 on Page 20 for the exterior wall recess
allowances of the square horizontal termination.
Termination Heights For Vents
Above Flat Or Sloped Roofs
Ref. NFPA 54 / ANSI Z223.1-2009
Roof Pitch *H (ft) *H (m)
Flat–6/12 1.0 0.3
6/12–7/12 1.25 0.38
7/12–8/12 1.5 0.46
8/12–9/12 2.0 0.61
9/12–10/12 2.5 0.76
10/12–11/12 3.25 0.99
11/12–12/12 4.0 1.22
12/12–14/12 5.0 1.52
14/12–16/12 6.0 1.83
16/12–18/12 7.0 2.13
18/12–20/12 7.5 2.29
20/12–21/12 8.0 2.44
The vent / air intake termination clearances
above the high side of an angled roof are as
shown in the following chart:
Figure 6: Horizontal Vent
Termination Clearances
6"
(152 mm)
12"
(305 mm)
Combustible Projection greater
Horizontal Vent Termination Clearances
Combustible Projection
2-1/2
inches or less in length
18"
(457 mm)
Ventilated
Soffit
Unventilated
Soffit
than 2-1/2 inches in length
Termination Kit
Side Elevation View
Termination Kit
All horizontal terminations
may be located as close as
6” (152mm) to any
(non-combustible and
combustible) exterior
sidewall. This distance
may be decreased to 2”
(51mm) for non--
combustible exterior
sidewalls only, if the
SV4.5HT-2 termination
is used.
Horizontal Vent Termination Clearances
The horizontal vent termination must have a minimum of 6 in. (152 mm) clearance to any
overhead combustible projection of 2 1/2 in. (64 mm) or less, see Figure 6. For projections
exceeding 2 1/2 in. (64 mm), see Figure 6. For additional vent location restrictions, refer to
Figure 7 on Page 7.
Figure 4: Multiple Terminations
12 in.
(305mm)
Minimum
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