Vertical Sidewall Applications
Since it is very important for the venting system to maintain balance between the combustion air intake and the flue gas exhaust, certain limitations as to vent configurations apply and must be strictly adhered to.
The Vent Graph shows the relationship between vertical and horizontal side wall venting and will help to deter- mine the various dimensions allowable.
Minimum clearance between vent pipes and com- bustible materials is 2”(51 mm) on top and 1” (25
mm)on the bottom and sides unless otherwise noted.
When vent termination exits through foundations less than 20” below siding outcrop, the vent pipe must flush up with the siding. It is always best to locate the fireplace in such a way that minimizes the number of offsets and horizontal vent length.
The horizontal vent run refers to the total length of vent pipe from the flue collar of the fireplace to the face of the outer wall.
Horizontal plane means no vertical rise exists on this portion of the vent assembly.
When installing the appliance as a rear vent unit, the 90° or 45° transition elbow is NOT INCLUDED in the following criteria and calculations, and unless specifically mentioned should be ignored when calcu- lating venting layouts.
•The maximum number of 90° elbows per side wall installation is three (3). (Fig. 20)
3 x 90° Elbows
FP1754
Fig. 20 Maximum three (3) 90° elbows per installation.
•If a 90° elbow is used in the horizontal vent run (level height maintained) the maximum horizontal vent length is reduced by 36” (914 mm). This does not apply if the 90° elbows are used to increase or redirect a vertical rise. (Fig. 21)
Vermont Castings DVR28 Direct Vent Gas Fireplace
Example: According to the vent graph (Page 11) the maximum horizontal vent length in a system with a 7.5’ (2.3 m) vertical rise is 20’ (6 m) and if a 90° elbow is required in the horizontal vent it must be reduced to 17’ (5.2 m). In Figure 21 Dimension A plus B must not be greater than 17’ (5.2 m).
In Figure 21, dimension A plus B must not be greater than 17’ (5.2 m).
•The maximum number of 45° elbows permitted per side wall installation is two (2). These elbows can be installed in either the vertical or horizontal run.
•For each 45° elbow installed in the horizontal run, the length of the horizontal run MUST be reduced by 18” (45 cm). This does not apply if the 45° elbows are installed on the vertical part of the vent system.
•The maximum number of elbow degrees in a system is 270°. (Fig. 22)
Example:
Elbow 1 = 90°
Elbow 2 = 45°
Elbow 3 = 45°
Elbow 4 = 90°
Total angular variation = 270°
B 7’
(178 cm)
A 10’ (254 cm)
| A + B = 17’ |
8’ | (518 cm) Max. |
(244 cm)
FP1755
Fig. 21 Maximum vent run with elbows.
1 + 2 + 3 + 4 = 270°
1
2
3
4
FP1756
Fig. 22 Maximum elbow usage. 
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