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Kitchen Exhaust fan duct sizing

Kitchen Exhaust fan duct sizing

Kitchen Exhaust fan duct sizing

(OP)
How do I size the duct for an exhaust fan with 1450 cfm and 1,324 rpm.    

RE: Kitchen Exhaust fan duct sizing

Are you talking residential kitchen or commercial kitchen?

RE: Kitchen Exhaust fan duct sizing

(OP)
Mechanical

RE: Kitchen Exhaust fan duct sizing

Fans have a performance curve that defines cfm vs. external pressure drop.

Step 1:  Find this curve for your fan.

Step 2:  Decide how many cfm you need, and use the curve to identify the corresponding allowed external pressure drop.

Step 3:  Size the duct for that pressure drop at the required cfm.

RE: Kitchen Exhaust fan duct sizing

marthab,

This isn't an exhaust hood over a cooking appliance, is it?  If so, you'll have to also consider keeping the velocity of the air high enough to entrain the particulates and grease.  If not a kitchen application, listen to MintJulep.

Good on ya,

Goober Dave

RE: Kitchen Exhaust fan duct sizing

Marthab
I do not know where you live, but here is a PDF of the code guidelines where I live. Most states are not that much different.
 Pay attention to page 10.

B.E.

http://www.sdcounty.ca.gov/deh/food/pdf/publications_ventilationguideline.pdf

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them.  Old professor

RE: Kitchen Exhaust fan duct sizing

Find and employ  a Mechanical engineer and don't try to bootstrap this.

RE: Kitchen Exhaust fan duct sizing

Berkshire
I am surprised that NFPA 96 is not part of the listed standards governing the design and installation of kitchen exhaust systems in your neck of the wood.

Also: NFPA 96 allows lower velocities as low as 500 FPM nowadays for some specific applications such as Melink control systems.

RE: Kitchen Exhaust fan duct sizing

It is and the guidelines mention it.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them.  Old professor

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