|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|
Exception: Where a listed condensing clothes dryer is installed prior to occupancy of the structure.
- 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; and
- The PVC ducts are solvent cemented.
Exception: The whole-house mechanical ventilation system is permitted to operate intermittently where the system has controls that enable operation for not less than 25-percent of each 4-hour segment and the ventilation rate prescribed in Table M1507.3.3(1) is multiplied by the factor determined in accordance with Table M1507.3.3(2).
|DWELLING UNIT |
|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 EXHAUSTED||EXHAUST RATES|
|Kitchens||100 cfm intermittent or 25 cfm continuous|
|Bathrooms-Toilet Rooms||Mechanical exhaust capacity of 50 cfm intermittent or 20 cfm continuous|