■Make sure there is a minimum of 18" (45.7 cm) of straight vent between the elbows if more than one elbow is used.
■Elbows too close together can cause excess turbulence that reduces airflow.
■Do not use a 5" (12.7 cm) elbow in a 6" (15.2 cm) or 3¹⁄₄" x 10" (8.3 x 25.4 cm) system.
■Do not reduce to a 5" (12.7 cm) system after using 6" (15.2 cm) or 3¹⁄₄" x 10" (8.3 x 25.4 cm) fittings.
■Avoid forming handmade crimps. Handmade crimps may restrict airflow.
■Use a
The length of vent system and number of elbows should be kept to a minimum to provide efficient performance.
The maximum equivalent length of the vent system is 60 ft (18.3 m). For altitudes above 4,500 ft (1272 m), reduce recommended vent run by 20% for best performance.
Cold Weather Installations
An additional back draft damper should be installed to minimize backward cold air flow and a thermal break installed to minimize conduction of outside temperatures as part of the vent system.
The damper should be on the cold air side of the thermal break.
Makeup Air
Local building codes may require the use of makeup air systems when using ventilation systems greater than specified CFM of air movement. The specified CFM varies from locale to locale.
Consult your HVAC professional for specific requirements in your area.
Venting Methods
Common venting methods are shown for a
Option 1 - Roof Venting | Option 2 - Wall Venting |
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A. 6" (15.2 cm) round roof | A. 6" (15.2 cm) round wall |
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Option 3 - Venting Between |
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Floor Joist |
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A | B | A | B |
A. Wall cap |
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B. 6" (15.2 cm) round wall | B. 6" (15.2 cm) round wall | ||
venting |
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