CSLB C-20 HVAC ContractorVentilation and Air DistributionEasy
Per the California Mechanical Code, what is the default maximum length of a clothes dryer exhaust duct (measured with two 90-degree elbows), unless a different length is otherwise permitted by the dryer manufacturer's installation instructions or an engineered calculation?
- A14 feet
- B25 feet
- C35 feet
- D10 feet
Show answer & explanationAnswer & explanation
Correct answer: A. 14 feet
The California Mechanical Code sets a default maximum dryer exhaust duct length of 14 feet with two 90-degree elbows, with deductions required for additional elbows, unless the manufacturer's instructions or a code-approved calculation allow a longer run.
Why the other options are wrong
- B. 25 feet exceeds the default without manufacturer approval or calculation.
- C. 35 feet is far beyond the default allowance.
- D. 10 feet is shorter than the code default.
Dryer Exhaust Duct Length
The CMC sets a default maximum clothes dryer exhaust duct length of 14 feet with two 90-degree elbows, with length reductions for additional elbows unless otherwise justified.
- Default max is 14 feet with two 90° elbows
- Additional elbows reduce allowable length
- Manufacturer instructions or engineering calculations can permit longer runs
Memory trick: Fourteen feet, two turns — that's the dryer duct's default rule.