Ductwork
G a s Downdraf t Cooktop
Duct Fittings
Use this form to compute maximum permissible lengths for duct runs to outdoors.
Note: Do not exceed maximum permissible equivalent lengths!
Flexible ducting: If flexible metal ducting is used, all the equivalent feet values in the table should be doubled. The flexible metal duct should be straight and smooth and extended as much as possible.
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| Total |
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| Equivalent | Quantity | Equivalent |
Duct Piece | Dimensions | Length* | Used | Length |
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| 1 ft. |
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| 6" round, | (per foot |
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| straight | length) |
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| 1 ft. |
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| (per foot |
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| straight | length) |
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| 6" |
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| 90° elbow | 15 ft. |
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| 6" |
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| 45° elbow | 9 ft. |
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| 90° elbow | 16 ft. |
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| 45° elbow | 5 ft. |
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Do NOT use flexible |
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plastic ducting. |
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| 90° flat elbow | 18 ft. |
Gas Downdraft
Cooktop
Model ZGU365 150' maximum equivalent length
Note: Any home ventilation system, such as a cooktop with a downdraft exhaust mechanism, may interrupt the proper flow of combustion air and exhaust required by fireplaces, gas furnaces, gas water heaters and other naturally vented systems. To minimize the chance of inter- ruption of such naturally vented systems, follow the heating equipment manufacturer’s guidelines and safety standards such as those published by NFPA and ASHRAE.
6" round |
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to |
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transition | 7 ft. |
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round to 6" |
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transition | 5 ft. |
6" round to |
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31⁄4" x 10" |
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transition |
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90° elbow | 20 ft. |
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round transition |
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90° elbow | 12 ft. |
6" round |
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wall cap |
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with damper | 21 ft. |
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wall cap |
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with damper | 27 ft. |
6" round |
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roof cap | 20 ft. |
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6" round |
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roof vent | 24 ft. |
* Actual length of straight duct plus duct fitting | Total Duct Run | |
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equivalent. Equivalent length of duct pieces are based |
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on actual tests conducted by GE Evaluation Engineer- |
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ing and reflect requirements for good venting |
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performance with any downdraft cooktop. |
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