Mike Hartigan wrote:
In article ,
says...
I'm finishing up my basement bar that includes a range with a grill.
These beasts tend to generate some smoke, so a vented exhaust is a
must. I've got a nice, beefy blower, but I'm concerned that the 20'
duct that will be installed above the suspended ceiling will leak
smoke and/or grease, particularly since the blower will be installed
at the hood, meaning that there will be positive pressure along the
entire length of the duct. How can I minimize this? 4" PVC would be
nice, but I suspect that it wouldn't be well suited to this
application (and probably not code). What are my options?
Sorry, guys. I thought it was a simple question. What kind of
ductwork is traditional, safe, and not overkill for a residential
range hood that is 20' from the most convenient exterior wall? Note
that I'm NOT planning to use PVC. And let's assume, just for grins,
that I know how to clean it.
I run about 20 ft from a pop-up down draft exhaust. In my experience
down drafts need more air flow than up flow exhausts. I used 8 in
spiral pipe, with a good sized FanTech axial blower. Size the pipe so
that the exhaust velocity is high, but not so high that you get
turbulent flow. Watch the Reynolds number. A pitot tube and a
Magnehelic gauge will let you get pretty close. Too large a pipe is as
bad as too small a pipe. I put a tee at the bottom of the vertical pipe
from the down draft to collect grease and provide access and a cast
aluminum access port in the side of the horizontal run. Cleaning is
messy but not difficult.
It works well.