Sorry, I am not sure where to ask this. I am putting in a basement bathroom and the fan my wife picked out is 110cfm because it has bluetooth/alexa speakers. However, it only has a 4" vent on back, and the ventilation code I could find says 100 is 10' max smooth metal, 125 is X (so no 4" vent), so 110 is probably X as well, Flex is X for 100. Unless:
Exception: Duct length shall not be limited where the duct system complies with the manufacturer's design criteria or where the flow rate of the installed ventilating equipment is verified by the installer or approved third party using a flow hood, flow grid or other airflow measuring device.
I contacted the manufacturer:
Hello,
There is no regulation on this, so the established Maximum is not obtained or tested for. The run should be the shortest run possible to the outside following the basic requirements.
Kind Regards,
I get, you want shortest run possible, but if 4" isn't even allowed, how can you even sell this crap? I guess I"m asking, am I reading the code wrong, is there anything I can do (upsize to 5" past the 4" connection point)?
Exception: Duct length shall not be limited where the duct system complies with the manufacturer's design criteria or where the flow rate of the installed ventilating equipment is verified by the installer or approved third party using a flow hood, flow grid or other airflow measuring device.
I contacted the manufacturer:
Hello,
There is no regulation on this, so the established Maximum is not obtained or tested for. The run should be the shortest run possible to the outside following the basic requirements.
Kind Regards,
I get, you want shortest run possible, but if 4" isn't even allowed, how can you even sell this crap? I guess I"m asking, am I reading the code wrong, is there anything I can do (upsize to 5" past the 4" connection point)?
Attachments
Last edited: