# special criteria for sizing grease duct?



## rwang (Dec 8, 2009)

Are there special guidelines for sizing kitchen exhaust vs general exhaust?

thanks in advance for the help!

rw


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## bconley (Mar 8, 2009)

rwang said:


> Are there special guidelines for sizing kitchen exhaust vs general exhaust?
> 
> thanks in advance for the help!
> 
> rw


The spec's of the hood fan you will be using will dictate the size of the ducting, and the size of the range or cooktop will dictate the size of the hood


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## Tom M (Jan 3, 2007)

the mechanical code offers requirements as well as the manufacturers specs. Smooth pipe for starters. The hood size must overhang the cook top by a certain amount as well. Some commercial ones require fire suppression to be interconnected.


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## bsybesma (Dec 8, 2009)

bconley said:


> The spec's of the hood fan you will be using will dictate the size of the ducting, and the size of the range or cooktop will dictate the size of the hood


This may be true for residential exhaust. For commercial grease duct, you need to maintain a certain velocity in order to get the grease out of the building. This design is dictated by from local mechanical code requirements.

Where is the project?


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## rwang (Dec 8, 2009)

bsybesma said:


> Where is the project?


The project is in Los Angeles.

Thanks for the help guys. I found the information I needed in Ch 5 of the CMC "exhaust systems".


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## fireguy (Oct 29, 2006)

is this a residential job or commercial? If this is a commercial job, & you did know where to find the calculations, you are not qualified to do the job. Sub it out to someone who is experienced.

Not to upset you, but I have only seen one HVAC company that installs Type I w/o deficiencies. Common problems are improper clearance to combustables, leaking welds, no access panels, wrong access panels, fans not hinged, no grease containment for the fan, power cords too short, wrong fans. If you do a poor job, people can get dead. 

You would be doing your customer a favor if you suggested they call 800.300.7832 for Bryan Exhaust Service, one of the best exhaust cleaners in hte LA area. 

You can flame me here or call me at 541.377.1143 to give me hell in person.


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## Remco Air (Jan 12, 2009)

First off you have to find out what exactly is going to be under your hood, grill, broiler, etc. this will then give you an idea as to what type of hood you need. Calculate the btu requirements, you will also need to figure out a constant velocity, volume of air, overhang, also take into account what size of a/c sys. is in the building, this will help you in sizing your make-up air sys. You have to get these calculations right or you could end up with negative press. in the building. I've seen this problem many of times. Most of the calcu. formulas can be found in the C.M.C. Good luck


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## bconley (Mar 8, 2009)

bsybesma said:


> This may be true for residential exhaust. For commercial grease duct, you need to maintain a certain velocity in order to get the grease out of the building. This design is dictated by from local mechanical code requirements.
> 
> Where is the project?


Which is dictated by the size of what is being vented


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## fabdraftdesign (May 25, 2009)

RWang:

Don't be too hasty with this... I've been desiging and installing Type-I hoods for 9 years. Before that I spent 12 years in the field.

While your California Mechanical Code (based on the Uniform Mechanical Code) will call for a certain exhaust rate per linear foot in Chapter Five, there is usually an exception for U.L. Listed hoods found in the beginning of the section (is it 507? I think that is the case for the International Mechanical Code.) I think it's UL 710 Listing.

The code minima are usually what's required if Billy Jo Sheetmetal Shop builds a hood, not if a major designer/manufacturer ENGINEERS it, designs it, tests it, U.L. lists it, and THEN builds it. I've always gotten positive results from Captive Aire... but some others that are (not as good but) similar include Gaylord, Halton, and Marshall Air.


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