22
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Example: If 20 feet total (H+H1) 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+
H1) 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 31.
V
H
H1
V1
Wall Firestop/Spacer
(SV4.5HF)
Ceiling
Firestop/Spacer
(SV4.5VF)
Whenusing Secure Flex
TM,
use Firestop/Spacer
SF4.5VF.
When using Secure
Flex, use Firestop/Spacer
SF4.5HF.
Wall Firestop/Spacer
(SV4.5HF)
See Table 8 on Page 20 as
an aid in venting component
selection for a particular
range of exterior wall thick-
nesses.
Figure 34 - Top Vent - THREE 90 DEGREE ELBOWS
LENNOX HEARTH PRODUCTS • MERIT® SERIES DIRECT-VENT GAS FIREPLACES • MODELS MLDVT-30/35/40/45 • INSTALLATION INSTRUCTIONS
HORIZONTAL VENT FIGURES / TABLES (continued)
Table F
H + H1 Maximum V Minimum
feet (meter) feet (meter)
5 (1.524)
Elbow Only
5 (1.524) 1 (0.305)
10 (3.048) 2 (0.610)
15 (4.572) 3 (0.914)
20 (6.096) 4 (1.219)
H + H1 = 20 feet (6.096 m) Max.
V + V1+ H + H1 = 60 ft. (18.3 m) Max.
Typical termination shown.