Commercial Cooking Recirculating Systems 2

[Ziggypump]

I have searched the site and have come up empty. Any help would be appreciated as I would like some opinions on how to properly size the airflow to the situation below.

An island kiosk type structure is to be built in the middle of a large open room. The owner wants the room to be able to cook and prepare food, so of course there are fryers and possibly some convection ovens. The code allows for a recirculating system, as since this kiosk is in the middle of the room with no good way of routing exhaust duct, an normal kitchen exhaust system is not allowed.

Per the code, "Factory-built commercial cooking recirculating systems" shall not be required to comply with exhaust code requirements. "Spaces in which these systems are located shall be considered to be kitchens and shall be ventilated" per ventilation table. "For the purpose of determining the floor area required to be ventilated, each individual appliance shall be considered as occupying not less than 100 sq. ft."

Now the ventilation table for kitchens only includes an exhaust flow rate, and using that last line of the code (2 fryers, 2 convection ovens) the square footage to determine airflow shall be 400 sq. ft. (though the actual space is less than that). At 0.7 cfm per sq. ft. required exhaust, 280 cfm is required. But with this being a recirc hood system, is this now the required OA?

This is where I'm getting hung up. The code states that recirc hood systems don't need to exhaust the air, but the ventilation schedule requires it. Does this code allow for indirect exhaust? Where the hood doesn't need to be exhausted but the room does?

Another problem arises with getting supply air to the room. An electrical closet in this space is situated away from the wall too, but a supply fan blows air from the building into the space, in an indirect supply fashion. Is this a possibility for supplying air into the kitchen?

I'm at the beginning of the design and am looking for some people with experience that may be able to help or offer solutions that I haven't thought of yet. The space is located in Michigan, and while they have their own code, it is based off of IMC 2012.

 

[EnergyProfessional]

Exhaust means directly outside. the code simply let's you use the regular kitchen exhaust instead of a dedicated hood. But either way, exhausting through the surrounding space would not be legal, nor good.

Unless their business model is to attract patrons by making the entire building smell like food.

you can use transfer air to make up for the exhaust

 

[Ziggypump]

Perfect. After letting this sit a bit, this is what I was beginning to believe would work.

I appreciate the help in understanding the issue.

 

[Compositepro]

I would be concerned about running deep fryers in a commercial setting without a hood over them. There will be oil mist mixed with the steam coming off and this is not good to breathe for long, and it will make housekeeping difficult. Also, don't you need fire suppression, which is usually part of the hood?

 

[Ziggypump]

Sorry I should have made this more clear, the recirculating system I'm talking about is a Recirculating hood. Thanks for the advice, and you are correct, fire suppression will be required in the hood. HerrKaLeun was helping me identify the exhaust and make-up air procedure. I was over complicating the system. The recirc hood is allowed, but a total exhaust for the kitchen is required, and since the hood is now accounting for 0% of the exhaust, the room exhaust must be utilized to achieve the code requirements. This recirc hood has some beefy filters to remove grease from the air being recirculated into the space. My understanding of these filters is that they will probably need to be changed often to maintain a healthy workspace.

 

[Compositepro]

I get it, thanks.

 

[berkshire]

Check your local code on grease Hood and Ducts. Grease ducts generally require heavy gauge welded ducts and are limited on horizontal run distance.
B.E.

You are judged not by what you know, but by what you can do.

 

[chicopee]

Before you do anything, you should read NFPA 96:Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations. I have not read that NFPA code for several years, so I don't know if recirculating systems are allowed in restaurants but back then, such system was not even mentioned. Also, your insurance carrier may drop your property insurance with your proposal, so double and triple check.
What I would proposed is a push-pull ventilation system for the kiosk that way you'll save on air conditioning and heating of the restaurant.

 

[urgross]

Definitely read NFPA 96 first, as you did not mention which interlocks you are including.

Attached web link may be of use:

http://fishnick.com/

 

[ornerynorsk]

Having been in the bar/restaurant business as a sideline for a number of years and directly involved in the specifying of a new commercial kitchen, I feel quite qualified to comment on this thread. Factory built commercial cooking recirculating systems refer to fryers and ovens that have the air handling and filtration built in, from the factory. (IE an Autofryer) They are not desirable, practical, nor economical. Filters require constant attention and will still turn the establishment into a French fry scented air freshener over time.

Almost all states will require a hood system with tempered make-up air, with exhaust flowing through hood filters to the outside of the building. The system must be tuned for slight negative pressure in the kitchen, so that kitchen air cannot exfiltrate to the customer area. You should be able to get a copy of a "Foodservice Construction Guide" from the health department or other regulating agency in your locale. The aforementioned NFPA guide is also a must-see, as is consultation with the insurance company. Any system will require built-in automatic fire suppression, as well, and a documented cleaning schedule.

Don't ignore plumbing requirements, either. There are some unique aspects in food service establishments.

Good luck!

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[Ziggypump]

Thank you for all of the advice, everyone. I've done kitchen work, but this situation is new to me, and I've never handled a recirc hood for a kitchen before. If given the choice, a direct exhaust system is installed. Everyone has been made aware of the issues with doing it this way, but they are bound and determined to have fryers and a griddle in this little back room in the middle of the space.

The kitchen will be exhausted at 0.7 cfm/sf with the provision of upping the square footage for each piece of equipment under the hood (the room is 330 sf, but we need to use 500 sf for exhaust calculations per code). Make-up air will be provided to the space the kitchen is installed in and transfer air from outside will flow into the kitchen, keeping the kitchen negatively pressurized.

Plumbing will be a pain, but we are still waiting on information from the kitchen consultant. Yes, one is on board, and they are the one specifying the recirc hood.

I'm not a fan of the recirc hood, but the client wants it, so I'm doing my best to make this kitchen operate as well as I can.