Exhaust Correction

[Meyer]

I am being asked by City of West Hollywood to provide calculation for exhaust ducts exceeding 14' in length. Anybody know what calculations is he referring to? Is it esp calculation?

 

[e hilton]

Actual cfm goes down as the length if the duct increases, and the number of turns decrease the efficiency more. Is he asking you to calculate the performance based on length and fittings?

 

[cda]

I am being asked by City of West Hollywood to provide calculation for exhaust ducts exceeding 14' in length. Anybody know what calculations is he referring to? Is it esp calculation?

Welcome


If not known, it is always good to ask the nice plan reviewer or inSpector,

The code section they are using.

So you can research it and assure it is applied correctly

 

[ICE]

14' comes into play with clothes dryers. The length of environmental air ducts serving exhaust fans is dictated by a fan's installation instructions. The installation instructions for a clothes dryer might result in a length greater than 14'.

504.4.2.1 Length Limitation. Unless otherwise permitted or required by the dryer manufacturer’s instructions and approved by the Authority Having Jurisdiction, domestic dryer moisture exhaust ducts shall not exceed a total combined horizontal and vertical length of 14 feet (4267 mm), including two 90 degree (1.57 rad) elbows. A length of 2 feet (610 mm) shall be deducted for each 90 degree (1.57 rad) elbow in excess of two.

You might need a bigger fan to achieve a certain cfm.

 

[Meyer]

14' comes into play with clothes dryers. The length of environmental air ducts serving exhaust fans is dictated by a fan's installation instructions. The installation instructions for a clothes dryer might result in a length greater than 14'.

504.4.2.1 Length Limitation. Unless otherwise permitted or required by the dryer manufacturer’s instructions and approved by the Authority Having Jurisdiction, domestic dryer moisture exhaust ducts shall not exceed a total combined horizontal and vertical length of 14 feet (4267 mm), including two 90 degree (1.57 rad) elbows. A length of 2 feet (610 mm) shall be deducted for each 90 degree (1.57 rad) elbow in excess of two.

You might need a bigger fan to achieve a certain cfm.

Nice!!! Well I was using the manufacturer's recommendation on the routing. So it really doesn't apply. Thanks ICE

 

[cda]

Nice!!! Well I was using the manufacturer's recommendation on the routing. So it really doesn't apply. Thanks ICE

Need to find the code section, the ahj is referring to