Lennox Merit MLDVT-35NM-FB Installation Instructions Manual page 17

LENNOX HEARTH PRODUCTS • MERIT
Table 18: Top Vent—Three Elbows
H + H Maximum
1
feet meters
5 1.524
5 1.524
10 3.048
15 4.572
20 6.096
H + H = 20 ft (6.1 m) maximum
1
V + V + H + H = 60 ft (18.3 m) maximum
1 1
Install the U-shaped vent restrictor in any vent run with more than 8 ft of
vertical rise (Figure 12).
If 20 ft of (H) horizontal vent run is needed, then 4 ft minimum
of (V) vertical vent will be required.
This table shows a 1 (V) to 5 (H) ratio. For every 1 ft of (V)
vertical, you are allowed 5 ft of (H) horizontal run, up to a
maximum horizontal run of 20 ft.
An elbow is acceptable as 1 ft of vertical rise except where an
elbow is the only vertical component in the system (Table 20).
SERIES DIRECT-VENT GAS FIREPLACES • MLDVT-30/35/40/45 • INSTALLATION INSTRUCTIONS
®
V Minimum
feet meters
Elbow Only
1 0.305
2 0.610
3 0.914
4 1.219
DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Ceiling
Firestop/Spacer
V 1
SV4.5VF*
H
H 1
*When using Secure Flex, use
Ceiling Firestop/Spacer SF4.5VF.
**When using Secure Flex, use
Wall Firestop/Spacer SF4.5HF.
Wall
Firestop/Spacer
SV4.5HF**
V
17