Mendota ML39 Assembly, Installation And Operating Instructions page 59

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.
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Using 90
The ML39 Fireplace by MENDOTA allows maximum flexibility in the use of 90
straight vertical section directly connected to the fireplace's starter collar determines the maximum horizontal run and the
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number of 90 elbows allowed for this fireplace.
For vent systems that provide a starting vertical section that is 4' to 12', you may connect up to 32' of horizontal pipe and up to
°
three 90 elbows. For all vertical terminations, four 90
°
Using 90
For vent systems that provide a starting vertical section less than 4' the following rules apply:
A. You must use the Master Venting Requirements Chart.
B. A single 90° vertical-to-horizontal elbow is already calculated into the allowable maximum horizontal run. The Venting
Requirements Chart assumes that for all horizontal runs calculated, one 90
Note: Each additional 90° elbow reduces the maximum horizontal distance allowed by 3'.
C. If you plan to use more than one 90
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' for each additional 90
Example: Assume you are using a 3' long starter vertical section. This should allow, per the Master Venting Chart, 22 ½' of
horizontal run. If you want to use three 90
for each elbow after the first elbow). This yields 16 ½ ' as the maximum horizontal run that you are allowed to
install using the 3' 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.
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. 32 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 to 12 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.
Zero Rise Horizontal Termination
The ML39 Fireplace must be installed by a qualified Mendota approved serviceperson.
A maximum horizontal run of 12" is allowed if a 9" vertical starter section and one 90° elbow is connected directly to this
fireplace's flue starter collar. The horizontal centerline of the 90ºelbow will be 59
fireplace.
85-03-01136
Elbows
Elbows When the Initial Starter Vertical Section Is Less Than 4'
°
elbow within the vent system, first use the Venting Requirements Chart and
o
elbows in the vent system. The length of the first
°
elbows can be used the fourth elbow must point vertically.
°
elbows, subtract 6' for two elbows from the 22 ½' maximum allowed (3'
ML39
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elbow is used within the venting system.
°
elbow you will use.
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inches up from the floor level of this
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