Installation instructions.
Duct Fittings
Use the chart at the right 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.
Do NOT use flexible plastic ducting.
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 interruption of such naturally vented systems, follow the heating equipment manufacturer’s guidelines and safety standards such as those published by NFPA and
ASHRAE.
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| Equivalent | Number | Equivalent |
Duct Pieces | Length* | Used | Length |
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| 6″ round, | 1 ft. |
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| straight | length) | feet |
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| 31⁄4″ x 10″ | 1 ft. |
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| (per foot |
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| straight | length) | feet |
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| 6″, 90° | 15 ft. |
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| elbow |
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| 6″, 45° | 9 ft. |
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| elbow |
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| 31⁄4″ x 10″ | 16 ft. |
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| 90° elbow |
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| 31⁄4″ x 10″ | 5 ft. |
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| 45° elbow |
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| 31⁄4″ x 10″ | 18 ft. |
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| 90° flat elbow |
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| 6″ round |
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| to 31⁄4″ x 10″ | 7 ft. |
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| transition |
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| 31⁄4″ x 10″ |
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| to 6″ round | 5 ft. |
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| transition |
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| 6″ round |
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| to 31⁄4″ x 10″ |
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| transition | 20 ft. |
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| 90° elbow |
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| 31⁄4″ x 10″ |
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| to 6″ round |
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| transition | 12 ft. |
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| 90° elbow |
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| 6″ round wall | 21 ft. |
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| cap with damper |
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| 31⁄4″ x 10″ wall | 27 ft. |
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| cap with damper |
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| 6″ round | 20 ft. |
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| roof cap |
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| 6″ round | 24 ft. |
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| roof vent |
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Total duct run should not exceed 150 ft.
*Actual length of straight duct plus duct fitting equivalent. Equivalent length of duct pieces are based on actual tests conducted by GE Evaluation Engineering and reflect requirements for good venting performance with any downdraft cooktop.
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