Range Hood Installation - Replace or Keep Existing Ducting

sprusgoose

Hey all. I'm in the process of doing a kitchen reno and recently purchased a range hood which I planned to use as a re-circulating unit. However, in the process of the demo, I discovered the original range hood ducting buried under a cabinet! The ducting is intact and runs to the exterior wall so no problems there. This range hood says it "recommends" 6" ducting (not "requires") and the existing is a 5" duct. The unit only puts out 400cfm so my question is, can I stick with the existing 5" and just use a reducer to put it all together, or will this be considerably more restrictive than the 6" duct? Any advice or calculations are welcome. Thanks!

sublime2

Can't see why not.Your not moving that much air that the 1" reduction would affect it.

Ironlight

There are hoods that move 800cfm through 6" ducts, so I think you'll be fine attempting to move 400cfm through a 5" duct which is roughly 66% the area of a 6". With more restriction your blower won't be as efficient, and you won't get a full 400cfm, but I doubt you're burn out the motor which is the primary concern.

lubertwillis

I agree with sublime2. You can. On this site you will find all kinds of best range hoods.