21
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT PLUS
®
DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
H Maximum
V Minimum
feet feet
5
(1.524)
1 (0.305)
10 (3.048) 2 (0.610)
15 (4.572) 3 (0.914)
20 (6.096) 4 (1.219)
V + H = 40 feet (12.2 m) Max.
H = 20 ft. (6.096 m) Max.
TABLE G
(meters)
(meters)
TABLE F
H Maximum V Minimum
feet
feet
3
(0.914)
Elbow Only
(meters)
(meters)
Example: If 20 feet of (H)
horizontal vent run is needed,
then 4 feet minimum of (V)
vertical vent will be required.
This table shows a 1 (V) to 5
(H) ratio. For every 1 foot of
(V) vertical, you are allowed 5
feet of (H) horizontal run, up
to a maximum horizontal run
of 20 feet.
Figure 36: Top Vent—ONE 90-DEGREE ELBOW—
ELBOW CONNECTION AT APPLIANCE
Figure 37: Top Vent—ONE 90-DEGREE ELBOW—
ELBOW CONNECTION NOT DIRECTLY AT APPLIANCE
Square termination (SV4.5HT-2) shown.
See Table 9 as an aid in venting component selection for a particular range of
exterior wall thicknesses.
Square termination (SV4.5HT-2) shown.
See Table 9 as an aid in venting component selection for a particular range
of exterior wall thicknesses.
Note: Install the U-shaped vent restrictor in any vent run with more
than 8 ft of vertical rise (See Page 13).
Venting Components Required for Various Exterior Wall Thick-
nesses, when using Typical Termination Kits
Vent Components Required Exterior Wall Thickness—in. (mm)
Termination Kit Only 6–9 1/4 (152–235)
Termination Kit and 6 in.
Vent Section (SV4.5L6)
10 3/4–14 (2733–356)
Termination Kit and 12 in.
Vent Section (SV4.5L12)
16 3/4–20 (426–508)
Termination Kit and
Telescopic Section
(SV4.5L12)
11 3/4–20 (299–508)
Table 9
Note: See Figure 34 showing wall thickness range
when using SV4.5HT-2 termination kit.
HORIZONTAL VENT FIGURES/TABLES
Note: 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 fi gures for
90 elbows, must be followed if 45 degree elbows are used.
Note: 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 in. per foot (20 mm per
meter) horizontal, in a direction away from the fi replace. The rise
per foot run ratios that are smaller are acceptable all the way down to
at or near level.
Note: SV4.5VF (Secure Vent
®
), SF4.5VF (Secure Flex) fi restop/spacer
must be used anytime vent pipe passes through a combustible fl oor or
ceiling. SV4.5HF (Secure Vent), SF4.5HF (Secure Flex) fi restop/spacer
must be used anytime vent pipe passes through a combustible wall.
Note: Secure Vent
®
components (rigid vent pipe and terminal) are
shown in the fi gures; Secure Flex
®
components (fl exible vent pipe and
terminal) may also be used.
Figure 35: Rear Vent—NO ELBOWS
WARNING
Under no circumstances, may separate sections of
concentric fl exible 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.
H
V
Ceiling
Firestop/
Spacer
SV4.5VF*
Wall Firestop/
Spacer SV4.5HF**
*When using Secure Flex, use
Ceiling Firestop/Spacer SF4.5VF.
**When using Secure Flex, use
Wall Firestop/Spacer SF4.5HF.
H
V
Wall Firestop/
Spacer
SV4.5HF**
**When using Secure
Flex, use Wall Firestop/
Spacer SF4.5HF.
Only the square termination (SV4.5HT-2) may be used.
See Table 9 as an aid in venting component selection for a particular
range of exterior wall thicknesses.
Note: Install the U-shaped vent
restrictor in any vent run with
more than 8 ft of vertical rise
(See Page 13).
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