|DRYER EXHAUST DUCT FITTING TYPE||EQUIVALENT LENGTH|
|4-inch radius mitered 45-degree elbow||2 feet 6 inches|
|4-inch radius mitered 90-degree elbow||5 feet|
|6-inch radius smooth 45-degree elbow||1 foot|
|6-inch radius smooth 90-degree elbow||1 foot 9 inches|
|8-inch radius smooth 45-degree elbow||1 foot|
|8-inch radius smooth 90-degree elbow||1 foot 7 inches|
|10-inch radius smooth 45-degree elbow||9 inches|
|10-inch radius smooth 90-degree elbow||1 foot 6 inches|
- The fan for overhead range hoods and downdraft exhaust equipment not integral with the cooking appliance shall be listed and labeled in accordance with UL 507.
- Overhead range hoods and downdraft exhaust equipment with integral fans shall comply with UL 507.
- Domestic cooking appliances with integral downdraft exhaust equipment shall be listed and labeled in accordance with ANSI Z21.1 or UL 858.
- Microwave ovens with integral exhaust for installation over the cooking surface shall be listed and labeled in accordance with UL 923.
- The duct is installed under a concrete slab poured on grade.
- The underfloor trench in which the duct is installed is completely backfilled with sand or gravel.
- The PVC duct extends not more than 1 inch (25 mm) above the indoor concrete floor surface.
- The PVC duct extends not more than 1 inch (25 mm) above grade outside of the building.
- The PVC ducts are solvent cemented.
|DUCT TYPE||FLEX DUCT||SMOOTH-WALL DUCT|
|Fan airflow rating
(CFM @ 0.25 inch wca)
|Maximum lengthc, d, e
|8 and above||NL||NL||NL||NL||NL||189||111||69||NL||NL||NL||NL||NL||NL||198||133|
- Fan airflow rating shall be in accordance with ANSI/AMCA 210-ANSI/ASHRAE 51.
- For noncircular ducts, calculate the diameter as four times the cross-sectional area divided by the perimeter.
- This table assumes that elbows are not used. Fifteen feet of allowable duct length shall be deducted for each elbow installed in the duct run.
- NL = no limit on duct length of this size.
- X = not allowed. Any length of duct of this size with assumed turns and fittings will exceed the rated pressure drop.
- Not less than 3 feet (914 mm) from property lines.
- Not less than 3 feet (914 mm) from gravity air intake openings, operable windows and doors.
- Not less than 10 feet (3048 mm) from mechanical air intake openings except where the exhaust opening is located not less than 3 feet (914 mm) above the air intake opening. Openings shall comply with Sections R303.5.2 and R303.6.
|NUMBER OF BEDROOMS|
|0 — 1||2 — 3||4 — 5||6 — 7||> 7|
|Airflow in CFM|
|1,501 — 3,000||45||60||75||90||105|
|3,001 — 4,500||60||75||90||105||120|
|4,501 — 6,000||75||90||105||120||135|
|6,001 — 7,500||90||105||120||135||150|
|RUN-TIME PERCENTAGE IN EACH 4-HOUR|
- For ventilation system run time values between those given, the factors are permitted to be determined by interpolation.
- Extrapolation beyond the table is prohibited.
|AREA TO BE |
|Kitchens||100 cfm intermittent or 25 cfm continuous|
|Mechanical exhaust capacity of 50 cfm|
intermittent or 20 cfm continuous