Lennox Hearth Products Direct Vent MPD-33 Series Installation Instructions Manual page 19

HORIZONTAL VENT FIGURES/TABLES (continued)
H 1
V
Figure 37
- Rear Vent - TWO 90 DEGREE ELBOWS
H 1
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.
An elbow is acceptable as 1 foot of vertical rise except where an elbow is the only vertical component in the system. See Figure 35.
See Table 4 on page 18 as an aid in venting component selection for a particular range of exterior wall thicknesses.
Figure 38
- Top Vent - TWO 90 DEGREE ELBOWS
H
*Wall
Firestop/Spacer
(SV4.5HF)
**Ceiling
Firestop/Spacer
(SV4.5VF)
*Wall Firestop/Spacer
(SV4.5HF)
H
*Wall Firestop/Spacer
(SV4.5HF)
**Ceiling
Firestop/Spacer
(SV4.5VF)
NOTE: DIAGRAMS & ILLUSTRATIONS NOT TO SCALE.
H Maximum
+H
1
feet (meters)
(1.524)
5
(3.048)
10
(4.572)
15
(6.096)
20
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.
See Table 4 on page 18 as an aid in venting component
selection for a particular range of exterior wall thicknesses.
(Square termination SV4.5HT-2 shown.)
V
(Square termination SV4.5HT-2 shown.)
TABLE H
H Maximum V Minimum
(meters) feet
feet
2 (0.610) 1
4 (1.219) 2
6 (1.829) 3
8 (2.438) 4
V + H + H 1 = 40 feet (12.2 m) Max.
H = 8 feet (2.438 meters) Max.
H + H 1 = 20 feet (6.096 meters) Max.
TABLE J
V Minimum
H + H Maximum
1
feet (meters) feet
(0.914) Elbow Only
3
(1.524)
5 1
(3.048)
10 2
(4.572)
15 3
(6.096)
20 4
H
V + + H = 40 feet (12.2 m) Max.
1
H + H = 20 ft. (6.096 m) Max.
1
(meters)
(0.305)
(0.610)
(0.914)
(1.219)
(meters)
(0.305)
(0.610)
(0.914)
(1.219)
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