Mendota M27 - Page 59

85-03-01120 M27 Page 59
Maximum Horizontal Run
• Maximum Horizontal Run allowed is 20 feet if a vertical starter section that is between 4 feet to 25 feet is connected
directly to this fireplace’s flue starter collar and no more than three (3) 90-degree elbows are used.
• Maximum Horizontal Run allowed is 48” if a 90-degree elbow 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 45 feet.
• Combined total length of all straight pipe sections in the vent system shall be less than 45 feet when using three (3) 90-
degree elbows or equivalent and terminating the vent system horizontally.
• Combined total length of all straight pipe sections in the vent system shall be less than 45 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 DEGREE ELBOWS
A single 90º vertical-to-horizontal elbow is already calculated into the allowable maximum 20' horizontal run. The Venting
Requirements Chart (Error! Reference source not found.) assumes that for all horizontal runs calculated, one 90-degree elbow i
s used within the venting system. Each additional 90º elbow reduces the maximum horizontal distance by 3'.
If you plan to use more than one 90-degree 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- degree elbow you will use.
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. Be sure to
maintain 1" air space to any combustibles (2" above horizontal runs).
Example 1: By using three 90º elbows the maximum horizontal distance has been reduced to 14 ft. (3 - 1 = 2 elbows x 3' = 6';
20’ Max. - 6' of elbows = 14' of horizontal run).
Example 2: If the first vertical section connected directly to the Fireplace is between 4 feet and 25 feet long, you are allowed a
maximum 20 feet of horizontal run. If you plan to use two (2) 90-degree elbows in the entire system, subtract three (3) feet
from the 20 feet maximum horizontal run calculated. Your maximum allowed horizontal run would then be 17 feet. Similarly, if
you plan to use three (3) 90-degree elbows, subtract 6 feet; from the 20 feet maximum horizontal run calculated to yield a 14
feet maximum allowed horizontal run in that venting system.
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 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.