Replies

1. 
   DanH | Nov 16, 2009 05:23am | #1

   It'll work -- a little less perfectly than with the right size duct, but it'll work. I suppose it could be a code issue, but probably not.

   A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter
2. 
   Scott | Nov 16, 2009 05:40am | #2

   My experience with reducing a range hood duct below the recommended size was not a happy one. Like Dan says, it will work, and it probably won't violate any code rules.

   But you may get all kinds of pulsating noise when the fan is on high speed and can't exhaust air the way it was designed to. If you're doing this job for a client I'd get it signed off with the reduced size so you don't get called back at your expense.

   In my case I was the contractor and owner, but I still tore it out and started again. After doing it right I'm much happier, and so is the fan.

   Scott.

1. 
   SoldotnaSteve | Nov 16, 2009 05:45am | #3

   thanks Scott

   that's what I needed to hear.

3. 
   kbd | Nov 16, 2009 10:23pm | #4

   I did it. If the run is short and not many elbows, it is not a problem.  Resistance to air flow is related to length of pipe but mostly elbows. Clean old duct well.

1. 
   SoldotnaSteve | Nov 16, 2009 11:27pm | #5

   how long is long?- this is a clean (one elbow) run (in actic) of 16 feet

   existing duct has never been used.

   thanks

1. 
   Clewless1 | Nov 18, 2009 04:07pm | #6

   Whatever you do ... seal the duct (no duct tape!!) and insulate it so the contents don't condense inside the duct ... over the years this can become a big fire hazard.

1. 
   Scott | Nov 18, 2009 07:46pm | #7

   >>>seal the duct (no duct tape!!)Why no duct tape? (Or do you mean the cloth stuff?) I think the foil-type duct tape would be OK.

1. 
   DanH | Nov 19, 2009 04:43am | #8

   Foil type should work. But remember to install the sections "backwards", with the narrow end pointing down so that the grease doesn't run through the seams and destroy the adhesive.
   A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter

2. 
   Clewless1 | Nov 19, 2009 03:33pm | #11

   Right, no grey/cloth duct tape. Use foil tape or duct mastic sealant. Duct tape good for everything but ducts.

3. 
   DanH | Nov 19, 2009 03:49pm | #12

   A bit of trivia: It's actually "duck tape", being originally invented as a utility tape made out of "duck" fabric. The name got corrupted into "duct tape", even though it never was intended for ducts.
   A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter

4. 
   rdesigns | Nov 19, 2009 06:10pm | #13

   Re trivia:  True or not--I like it.

    

5. 
   DanH | Nov 20, 2009 03:56am | #14

   http://en.wikipedia.org/wiki/Duct_tape
   A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter

6. 
   Clewless1 | Nov 22, 2009 06:33pm | #15

   Ain't that just really interesting ... really it is!! Nice piece of trivia. And duct tape has gone to the moon and back! wow!!

4. 
   reinvent | Nov 19, 2009 05:32am | #9

   It is important to pick the right duck for the job.;-)

1. 
   Jeff_Clarke | Nov 19, 2009 06:40am | #10

   Viaduct?View Image

5. 
   wookie | Nov 23, 2009 12:05am | #16

   Do not run duct backwards, it will create turbulence not good for air flow. Roof cap is a consideration. Typical  " T " types restrict air flow. China cap with a cone diverter on bottom works great , but only available at sheet metal shop usually. Put ascreen on it. Go with duct size required.

    

   wookie