85-03-01107 FV34 DECOR Page 61
B. Combined total length of all straight pipe sections in the vent system shall be less than 40 feet when using three (3) 90-
degree elbows or equivalent and terminating the vent system horizontally.
C. Combined total length of all straight pipe sections in the vent system shall be less than 40 feet when using four (4) 90-
degree elbows or equivalent and terminating vertically.
How to Calculate the Vent Lengths
For calculation purposes and usage of charts in this manual, simply add the lengths of all individual straight pipe
sections. For example: if you use two 2-foot lengths and one 4-foot length, the total vent system length will be 2+2+4
= 8 feet.
Using 90
0
Elbows
A. The FV34 DECOR Fireplace by MENDOTA allows maximum flexibility in the use of 90
o
elbows in the vent
system. The length of the first straight vertical section directly connected to the fireplace’s starter collar
determines the maximum horizontal run and the number of 90
0
elbows allowed for this fireplace.
B. For vent systems that provide a starting vertical section that is 5 feet or longer, you may connect up to 25 feet of
horizontal pipe and up to three (3) 90
0
elbows. But be certain to deduct 3 feet for the 2nd and Third 90
o
elbow
(ignore the first 90
o
elbow which is already compensated for in the maximum allowed 25 feet horizontal maximum
run)
Using 90
0
Elbows with Starter Vertical Section Less Than 5 Feet
For vent systems that provide a starting vertical section less than 5 feet, the following rules apply:
A. You must use the Master Flue Venting Requirements Chart. See the area below the 5’ vertical run line.
B. A single 90º vertical-to-horizontal elbow is already calculated into the allowable maximum 25' horizontal run. The
Venting Requirements Chart assumes that for all horizontal runs calculated, one 90
0
elbow is used within the venting
system. Each additional 90º elbow reduces the maximum horizontal distance allowed by 3'.
C. If you plan to use more than one 90
0
elbow within the vent system, first use the Venting Requirements Chart (Figure
14) and calculate the maximum horizontal run you are allowed based on the first vertical section connected directly to
the fireplace. From this maximum horizontal run calculated, subtract 3 feet for each additional 90
0
elbow you will use.
Example 1: Assume you are using a 3 feet long starter vertical section. This should allow, per the Master Venting Chart, 11 feet
of horizontal run. If you want to use three 90
0
elbows, subtract 6 feet for two elbows from the 11 feet maximum allowed [3
feet for each elbow after the first elbow]. This yields 5 feet as the maximum horizontal run that you are allowed to install using
the 3-foot vertical starter section.
CAUTION: If a vertical-to-horizontal discharge elbow or a horizontal-to-horizontal discharge elbow is enclosed within a wall,
floor or ceiling, a top air space clearance of 3" must be maintained above the entire body of the elbow.
CAUTION: If a vertical-to-horizontal discharge elbow or a horizontal-to-horizontal discharge elbow is enclosed within a
wall, floor or ceiling, a top air space clearance of 3" must be maintained.
Using 45-Degree Elbows
Two 45-degree elbows may be used in place of one 90-degree elbow. On 45-degree runs, one foot of diagonal pipe is
equal to 8-1/2 inches horizontal run and 8-1/2 inches vertical run.
Two 45-degree elbows may be connected directly to the top of this fireplace to create a horizontal offset. 25 feet
maximum horizontal run allowed with this offset configuration only if the first vertical section connected directly to the
last 45-degree elbow is more than 5 feet long. For maximum allowable horizontal distances with the 45-degree offsets,
see the Master Venting Configuration Chart.
Note: Each horizontally positioned 45º elbow reduces the maximum horizontal distance by 1½ '.
SUPPORT: Horizontal runs of pipe will require one vent support for every 3 ft. of pipe.
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