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6 inch to 4 inch Reduce - 1.5ft duct

Posted by blistex (My Page) on
Mon, Nov 11, 13 at 22:31

Hi all,

Another duct size question.

I've read to never reduce your duct size with a duct reducer for the range as the airflow is affected by the smallest point of it. But I was just wondering, if the length matters at all.

My kitchen's duct is 4 inches leading outside. length is 1.5 feet (this includes one 90 degree elbow). I have tried to remove it, but it seems the elbow is making it difficult to wiggle out as it is screwed to the straight duct.

The range hood I have is 600 cfm. I have an electrical coil top. I really don't plan on using the highest setting much.

Or should I continue to go with trying to replace it with a 6" duct.


Follow-Up Postings:

RE: 6 inch to 4 inch Reduce - 1.5ft duct

If you are happy with something under 300cfm, and more noise, you can use the 4 inch. You aren't going to 600cfm, even with 6 inch.

If you have a fan curve (cfm vs. static pressure), a calculation can be made.

Do you have a make/model for your hood/blower?

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