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IMPORTANT VENTING CONFIGURATION NOTES
High Altitude Installation Information
: Prior to installing at altitudes higher than 7500, please contact the Mendota tech-
nical service department for specific venting requirements and venting restrictions.
Maximum Horizontal Run
Maximum Horizontal Run allowed is 32 feet if a vertical starter section that is between 4 feet to 10 feet is connected directly
to this fireplace’s flue starter collar and no more than one (1) 90 degree elbow is used.
Maximum Horizontal Run allowed is 6” if an 18” vertical starter section is connected directly to this fireplace’s flue starter
collar.
Maximum Vent System Length
Combined total length of all straight pipe sections in the vent system shall be less than 42 feet.
Combined total length of all straight pipe sections in the vent system shall be less than 42 feet when using three (3) 90-
degree elbows or equivalent and terminating the vent system horizontally in Zone “B”.
Combined total length of all straight pipe sections in the vent system shall be less than 42 feet when using four (4) 90-
degree elbows or equivalent and terminating vertically.
How To Calculate The Vent System 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 in Zone “B”
The ML39 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.
For vent systems that provide a starting vertical section that is 4 feet or longer, you may connect up to 32 feet of horizontal
pipe. For each 90
o
elbow installed after the first 90
o
elbow on top of the first 4 ft. section connected to the starter color of
this fireplace, reduce maximum allowed horizontal run by 4 feet.
Using 90
o
Elbows in Zone “A”
For vent systems that provide a starting vertical section less than 4 feet, the following rules apply:
a. You must use the Master Flue Venting Requirements Chart. See Zone “A” below the 4’ vertical run line.
b. A single 90
º
vertical-to-horizontal elbow is already calculated into the allowable maximum 32' 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 90
º
elbow reduces the maximum horizontal distance by 4'.
c. If you plan to use more than one 90
0
elbow within the vent system, first use the Master Flue Venting Requirements Chart
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 4 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 Master Flue Venting
Requirements Chart, 19 feet of horizontal run. If you want to use three 90
0
elbows, subtract 8 feet for two elbows from the
19 feet maximum allowed [4 feet for each elbow after the first elbow]. This yields 11 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 elbow body.
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 vent
starter adapter on this fireplace to create an offset to provide the required clearances to combustible framing or sheathing
materials.
Two 45-degree elbows may be connected directly to the top of this fireplace to create a horizontal offset. 20 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 4 feet long. For maximum allowable horizontal distances with the 45-degree offsets, see the Master
Venting Configuration Chart.
NOTE:
Each horizontally positioned 45
º
elbow reduces the maximum horizontal distance by 1½ '.
Support
: Horizontal runs of pipe will require one vent support for every 3 ft. of pipe.
