22
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT PLUS
®
DIRECT VENT GAS FIREPLACES (MPDP35/40) • INSTALLATION INSTRUCTIONS
See Table 8 as an aid in venting component selection
for a particular range of exterior wall thicknesses.
Figure 43: Top Vent - ONE 90-DEGREE ELBOW
Typical termination shown.
H
V
When using Secure Flex,
use Firestop/Spacer
SF4.5VF.
Ceiling
Firestop/Spacer
(SV4.5VF)
When using Secure Flex,
use Firestop/Spacer
SF4.5HF.
Wall Firestop/Spacer
(SV4.5HF)
Min. One
Foot Vent
Section
Required
Example: If 20 feet of (H)
horizontal vent run is needed,
then 4 feet minimum of (V)
vertical vent will be required.
Note:
• An elbow may NOT be at-
tached directly to the vent
collar.
• Install the U-shaped vent
restrictor in any vent run with
more than 8 ft. of vertical
rise. See Pages 13 and 14.
* Minimum 1 ft. section and
elbow
TABLE E
H Maximum V Minimum
feet (meters) feet (meters)
3 (0.914) * (0.061)
7 (2.134) 3 (0.914)
11 (3.35) 4 (1.22)
14 (4.267) 5 (1.524)
18 (5.49) 6 (1.729)
20 (6.2) 7 (2.134)
V + H = 40 feet (12.2 m) Max.
H = 20 ft. (6.096 m) Max.
Venting Components Required for Various Exterior Wall Thick-
nesses, when using Typical Termination Kits
Vent Components Required Exterior Wall Thickness - inches (mm)
Termination Kit Only 6 to 9-1/4 (152 to 235)
Termination Kit and 6 In. Vent
Section (SV4.5L6)
10-3/4 to 14 (273 to 356)
Termination Kit and 12 in.
Vent Section (SV4.5L12)
16-3/4 to 20 (426 to 508)
Termination Kit and Tele-
scopic Section (SV4.5L12)
11-3/4 to 20 (299 to 508)
Table 8
Note: See Figure 41 showing wall thickness range
when using SV4.5HT-2 termination kit.
Only the square termination (SV4.5HT-2) may be used.
HORIZONTAL VENT FIGURES/TABLES
See Table 8 as an aid in venting component selection
for a particular range of exterior wall thicknesses.
Note:
• Secure Vent
®
components (rigid vent pipe and terminal) are shown in
the figures; Secure Flex
®
components (flexible vent pipe and terminal)
may also be used.
• Two 45-degree elbows may be used in place of one 90 degree elbow.
The same rise to run ratios, as shown in the venting figures for 90
elbows, must be followed if 45-degree elbows are used.
• It is very important that the horizontal/inclined run be maintained
in a straight (no dips), slightly elevated plane. The recommended
incline is approximately 1/4" per foot (20 mm per meter) horizontal,
in a direction away from the fireplace. The rise per foot run ratios
that are smaller are acceptable all the way down to at or near level.
• SV4.5VF (Secure Vent), SF4.5VF (Secure Flex) firestop/spacer must be
used anytime vent pipe passes through a combustible floor or ceiling.
SV4.5HF (Secure Vent), SF4.5HF (Secure Flex) firestop/spacer must be
used anytime vent pipe passes through a combustible wall.
Figure 42: Rear Vent - NO ELBOWS
WARNING
Under no circumstances, may separate sections of
concentric flexible vent pipe be joined together.
H
H = 28 in. (711 mm) Maximum.
7 in
(178 mm)
Wall Firestop/
Spacer
SV4.5HF**
**When using Secure Flex, use
Wall Firestop/Spacer SF4.5HF.
Remove inside rear vent restrictor if vented over 7" horizontally
(see Page 13).
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