Flexible air connector

[Sifu]

I was reading old posts and came across a link to a Hart & Cooley page of FAQ's. On that page it says that flex air connectors are not limited in length in bathroom exhausts because current codes don't have a reference to bathroom exhausts. IMC chapter 6 includes exhaust systems, of which a bathroom fan is one. Back when I did mechanical inspections we enforced the 14' limitation in bath exhausts. Is it me or Hart & Cooley that has it wrong?

 

[globe trekker]

Is it me or Hart & Cooley that has it wrong?

Did Hart & Cooley list some type of standard, and can you actually enforce the IMC?

Section 603.6.2.1 of the 2006 IMC limits the flexible connector length to 14 ft.

This would be the "more restrictive" standard to apply.

Their product literature states that they do comply with the IMC.

 

[Gregg Harris]

I was reading old posts and came across a link to a Hart & Cooley page of FAQ's. On that page it says that flex air connectors are not limited in length in bathroom exhausts because current codes don't have a reference to bathroom exhausts. IMC chapter 6 includes exhaust systems, of which a bathroom fan is one. Back when I did mechanical inspections we enforced the 14' limitation in bath exhausts. Is it me or Hart & Cooley that has it wrong?

Hart and Cooley's FAQ document is wrong. The testing for the flexible connector under UL181 is limited by design to a maximum of 14 feet by excluding it from smoke, puncture and impact testing.

 

[Daddy-0-]

The code does not require a bath fan but it does require ventilation in a bathroom if it has a shower or tub. This requirement is to allow the removal of moisture not stink. An operable window will meet the code requirements. If they install a fan it must be compliant which would include a 14' max for air connectors.

 

[Sifu]

Just wanted to make sure I was understanding it correctly. I have yet to see it enforced correctly here and when you are one guy seeing it differently than all the rest it never hurts to do the research. I was just thrown off by the Hart & Cooley position that a bath exhaust is not an exhaust. BTW how did those links get put in my OP? I didn't do it or if I did I didn't mean to.

 

[globe trekker]

You are on the right track Sifu! The links get installed automatically by

the combination of words. They don't really mean anything, just one of

the (many) benefits of the software platform installed on this forum.

 

[klarenbeek]

IMO, the duct going from the bath fan to the exterior is just that: duct. It would need to meet all the same requirements as any other HVAC duct, including the 14' length limit for flex air connectors

 

[Gregg Harris]

One big element that gets overlooked and rarely ever tested is, does the fan have enough available static to overcome whatever is connected to it.

The exhaust fan is not only removing odder but moisture laden air that can and will condense inside the duct if not sized and run without bends and kinks.

 

[Sifu]

It might get overlooked it might not. I would like to see bigger & better fans but the residential code only requires a 50 cfm fan without regard for the distance of the exhaust. Its dificult for me at least to require bigger fans and calculations when the code gives us the 50 cfm and no length restricitions. JLC had a pretty good article a couple issues back about this topic.

 

[Robert Ellenberg]

14' is the limit for flex connectors. There is a higher grade flex duct that does not have the 14' restriction.