Modulex EXT Vent and Combustion Air Application Guide
TAG-0054_0F
AERCO International, Inc.
•
100 Oritani Dr.
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Blauvelt, NY 10913
Page 27 of
28
GF-136–V
Phone: 800-526-0288
09/25/2017
The maximum pressure drop of the combustion air piping is also 100 equivalent feet (30.5 m). See
Section 2.3. Note that this does
NOT
mean that the allowed combined pressure drop between the
vent and combustion air is 200 equivalent feet (61 m). That is, the vent cannot go above 100
equivalent feet (30.5 m), even if the combustion air is less than 100 equivalent feet, and vice versa.
Example:
The vent system of two MLX-802/800 (2 x 802,000 BTU/hr. = 1,604,000 BTU/hr.) consists of 30 foot
length of vent pipe and 2 sharp 90° elbows. A termination vent or rain cap is also installed. Each
individual vent connector consists of 5 ft. straight run and one WYE.
•
Common Vent pipe: 30 ft. + (2 x 10ft) + 5 ft. = 55 equivalent ft. (16.7 m)
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Individual vent connector: 5 ft. + 5 ft. = 10 equivalent ft. (3.0 m)
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Total Vent equivalent length: 55 ft. + 10 ft. = 65 (19.7 m)
60 equivalent ft. is LESS than 100 equivalent feet: OK to use 8” Common vent piping and 6”
individual connectors.