GF-5050
Innovation Series & ReCon Water Heater
TAG-0043_0Q
Venting and Combustion Air Guide
Page
16
of
39
AERCO International, Inc.
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100 Oritani Dr.
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Blauvelt, New York 10913
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Phone: 800-526-0288
12/01/2016
Rule-of-Thumb Examples – Standard North American units of measure:
1. A 40 foot length of combustion air pipe and 1 sharp 90° elbow plus two termination 90° elbows
add up to 40 ft. + 10 ft. + (2 x 10 ft.) = 70 equivalent ft.
2. A 30 foot (9.1 m) length of combustion air pipe and 2 sharp 90° elbows plus two termination
90° elbows add up to 30 ft. + (2 x 10 ft.) + (2 x 10 ft.) = 70 equivalent ft. (21.3 m).
Rule-of-Thumb Examples – Metric units of measure:
1. A 12 m length of combustion air pipe and 1 sharp 90° elbow plus two termination 90° elbows
add up to 12 m + 3 m + (2 x 3 m) = 21 equivalent m
2. A 9 m length of combustion air pipe and 2 sharp 90° elbows plus two termination 90° elbows
add up to 9 m + (2 x 3 m) + (2 x 3 m) = 21 m
For more detailed analysis see sections 3.6 and 3.7 and Example.
2.5. COMMON COMBUSTION AIR SYSTEMS
In many installations, the combustion air duct can be manifolded for multiple unit applications.
The length and restriction of the ducted combustion duct directly impact the size, length and restriction
of the discharge venting. The direct vent air intake should be located at least 3 feet (1 m) below any
vent termination within 10 feet (3.1 m).
A screen with mesh size not smaller than 1” x 1” (25 mm x 25 mm) must be installed at the inlet of the
ducted combustion air duct.
For systems using manifolded ducted combustion, use the longest length of common duct and the
individual branch to the furthest boiler to calculate the pressure drop. Figures 7a and 7b illustrate
preferred and acceptable designs.
