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Help Figure Out Exhaust Hood And Makeup Air Needs?

Posted by johnliu (My Page) on
Wed, Feb 3, 10 at 13:27

I am starting to think about the ventilation for my kitchen remodel. I wonder if I can get some ideas and advice, please?

Here is my situation:
- The ranges I am considering are commercial 36-inch or 48-inch ranges, so either 6X or 8X burners of appx 33K BTU/hr each. I like to sear, wok, fry, and expect to generate a good amount of smoke, grease, effluent, etc. Although, I wouldn't be doing smoky stuff on more than a couple burners at a time.
- The range will be placed against a wall and will be free-standing, meaning no cabinetry on either side. If I get a 36-inch range, there may be a narrow (15") steel filler table on the side adjacent to a traffic aisle. If I get a 48-inch range, there may be a stainless steel guard shielding the traffic side of the range.
- The wall will have a non-combustible surface, maybe concrete board with an air gap to the studs (still planning), and that surface will either be tiled or sheathed with stainless steel.
- The other side of the wall is the stairwell down to the basement and side door, so ducting can go out the rear of the hood, through the wall into the stairwell, make a 90-deg turn, and through the exterior wall. Ducting of any reasonable size can fit and I don't mind having it exposed in the stairwell. A blower would fit there too.
- The floor is stone tile. Under the floor is the laundry area of the unfinished basement, and ducting can fit down there as well.
- The ceiling is a little under 9 feet. Above the ceiling is the second floor, so ducting in the ceiling is not a good option, it would be very constrained in size.

My tentative idea for the vent hood is to use a ceiling-mounted hood, about 1 foot wider and deeper than the range, so 4 feet wide by 3 feet deep if I get a 36-inch range. Something vaguely along these lines:
http://www.acitydiscount.com/Used-Restaurant-Kitchen-Grease-Exhaust-4ft-Hood-Stainless-Steel.0.105252.1.1.htm The bottom front edge of the hood needs to have at least 6 ft 5 in headroom, so it would be appx 40 inches higher than the burners, but the bottom rear edge could be lower.

So, here are my specific questions, and I'm sure I'm missing some issues too.

1. How do you calculate the required exhaust CFM? Is there a formula based on total range BTU/hr? How do you factor in the placement and dimensions of the hood?

2. How do you calculate the required makeup air CFM? Since I don't have any information of how leaky my house is (it is an old house, that's all I know), I was going to guessestimate something like makeup CFM >= exhaust CFM less 300 CFM. Does that make sense?

3. Where should the makeup air come in? I've seen some commercial hoods where the makeup air comes in at the front edge of the hood, while the exhaust air is pulled from the back edge. Alternatively, I could bring some or all of the makeup air in through a floor vent located under the range.

4. Do I need to heat the makeup air? It is typically 30-40F in winter here. Then again, I won't be running the range 12 hours a day - I might be searing or woking for 10 minutes, for the rest of the cooking I would turn the blowers down. Do you think that bringing the makeup air in through the hood, or under the hot range, would mitigate any heating needs?

5. I am not so wild about having a giant lump of stainless steel filling the ceiling, so I was thinking about constructing a wooden hood, style consistent with the upper cabinets, and using a steel hood liner in that. What do you think?

6. Has anyone had a custom hood or hood liner built by a local sheet metal shop? Did you find that was better, or cheaper, than buying a hood?

My impression is that, when all is said and done, the venting may end up costing me more than the range.

Thanks for helping. Sorry if this topic is kind of arcane.(My next question will be on fire suppression . . . )


Follow-Up Postings:

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RE: Help Figure Out Exhaust Hood And Makeup Air Needs?

The first place you stop is your local building permit office. Many areas do not permit the use of commercial ranges in a home environment, period. Those that do will have an extensive list of requirements that you will have to do to be able to do this. Those requirements may or may not work with your intended location. They will include specifications for venting fire suppression, and makeup air. No point in guesstimating what your local authorities will require. Ask them.

THe second place you need to talk to is a commercial HVAC company that specializes in restaurant ventilation installments. Professional equipment means professional design and installation. That pretty much eliminates the DIY approach unless you are a licensed HVAC person. YOu will also need to have a ERV attached to that makeup air, plus greatly upgrade your home's air conditioning. Those ranges are not at all insulated, and a good deal of the heat they produce will be added to your home's AC load. A restaurant kitchen in the middle of a Southern summer is a miserable place to be, and that's what your kitchen will resemble unless you have a pro engineer the integaration of everything.

The onerous reqirements of professional equipment are the reason most folks in search of "restaurant quality" home cooking experiences end up purchasing a prosumer type range that is designed with safety (and insulation)in mind for a home environment.


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Rule Of Thumb Suggests 1,500 CFM?

I found the link below that suggests I might start thinking at 1,500 CFM for a 4 foot wide, 3 foot deep hood mounted against a wall. 4 x 3 x 125 = 1500. Then I guess I'd want to adjust up since the hood will be mounted rather high?

Here is a link that might be useful: Rule of Thumb formula


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Well . . .

Thanks. I recognize that under some scenarios I might have to install commercial-grade HVAC and automatic fire suppression, have my house licensed as a business, have my neighhorhood re-zoned as commercial, find another place to live, change my profession to restauranteur . . .

But at this point I am trying to learn what is functionally required, rather than what is bureaucratically required.


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RE: Help Figure Out Exhaust Hood And Makeup Air Needs?

While I appreciate your enthusiasm for cooking in your new space, I think the idea of all those btus in a relatively small home setting is overkill (seriously). You should get a standard residential range (like a Bluestar) and get a separate 30000btu wok burner all under the same large hood. Do you really have 8 stir fries going at once?

A hood as high and deep as you are suggesting would be really intrusive. Minimum cfm is 100 per 10000 btu, so on a 48" range with 8 burners and 2 gas ovens, you would need 3000cfm. A 36" would require 2100cfm minimum. I had a 60" vulcan with mere 22000 btu burners, salamander, and single oven covered by about 1600 cfm (a little under recommended, but close enough). I was never able to have it professionally cleaned or serviced because the repair people did not have insurance to come into a home. You will likely not have any warranty (though these machines are basic if you want to maintain it yourself). It was installed 35 years ago by a previous owner, but if it were done today, I would have to have all the fire suppression system/upgraded HVAC/make up air stuff installed.


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RE: Help Figure Out Exhaust Hood And Makeup Air Needs?

Histokitch mentioned insurance. You should also check with your home insurance provider. I expect that the range you want, with 33k btu/each burner, and minimal insulation, will increase your insurance premiums. If you omit informing your insurance provider about this non-residential range, and there is a fire in your home, or a visitor is burned from touching the oven door and sues you, you may find you've not conformed to your insurance requirements, and not be covered.

Also, how heavy is the commercial range, particularly the 48" one? Do you have any concerns that your floor can support the weight?


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RE: Help Figure Out Exhaust Hood And Makeup Air Needs?

Look, you sound like a guy who wants to plan this correctly. You're talking the talk. Walk the walk. Check with the experts who will determine if what you are planning is feasable.

Building codes are there to protect you and your neighbors. A fire can spread from one single family home to another. That's why they have regulations about fire producing implements in your home. You'd have to have the design and installation of a new fireplace permitted and inspected as well. It's not BS bureaucracy. It's public safety, and an improper install endangers more than just your own property and life. And that is why you check with your local building office before you start planning something that may not be allowed. There is no point in planning something that you can't end up doing. That's a waste of your time and money.


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My Thought Process

I have checked with my insurance company. They don't care if I put a commercial, non-residential range in my kitchen. I'd notify them in writing before proceeding, of course.

Weight should not be an issue. 36-inch to 48-inch ranges weigh from 600 to 800 pounds, which is about five people. The basement is unfinished, so if I measure any deflection I can sister the joists or even add a post.

I've talked to a local restaurant supply store. They are happy to sell me a used range. For a new range, they want to sell to a business, which I can do. They will only deliver to my front door, will not install, and the range will have no warranty - all perfectly understandable.

The applicable building code has no provision for commercial appliances in residential dwellings. Then again, I've never pulled a building permit just to buy a new kitchen appliance. Interestingly, the code says nothing meaningful about makeup air or required CFMs in residential kitchens - I will look again, though.

Visually - hmm. I did a quick sketch - maybe I can make this look palatable, maybe not.

rangehood1

So, this brings me to the original issue, which is function and safety.

I have friends with commercial ranges in their home kitchens. These ranges don't set the kitchen ablaze, nor do they turn the kitchen into a sauna, nor do they brand you like a calf if you brush up against them. They are not ''on'' at full-bore 12 hours/day, jammed in a room with more ranges, broilers, griddles, ovens, fryers, all working non-stop.

I believe that, if properly installed with appropriate clearance to combustibles and appropriate venting and professionally installed gas connections, a commercial range is just as safe as any range. When I add the fire suppression and gas shut-off, I think it'll be safer.

But I do need to get the venting right. This house is leaky, but hopefully as we work on it, it'll get tighter, and I don't want any backdrafting.

The way I see it, the exhaust and makeup issues I'm wondering about are not unique to commercial ranges. Someone planning a 60-inch "professional" range with char-broiler would face the same issues. I know that discussions about commercial appliances on GW tend to elicit cautionary responses, which I understand and appreciate. But, for the purposes of planning HVAC, let's forget the "commercial" aspect. Let's pretend I'm planning a 60-inch Bluestar and for some reason I like to cook with burners on high and the oven door ajar and the char-broiler blazing.


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RE: Help Figure Out Exhaust Hood And Makeup Air Needs?

I don't know which brand you are thinking about, but specs for everything are online. Here is the ones for a Vulcan 36' range:

A pressure regulator sized for this unit is included. Natural gas
5.0' W.C., propane gas 10.0' W.C.
2. Gas line connecting to range must be 1' or larger. If flexible
connectors are used, the inside diameter must be 1' or larger.
3. An adequate ventilation system is required for commercial
cooking equipment. Information may be obtained by writing to
the National Fire Protection Association, 1 Batterymarch Park,
Quincy, MA 02269, www.NFPA.org. When writing, refer to NFPA
No. 96.
4. These units are manufactured for installation in accordance with
ANSZ223.1A (latest edition), National Fuel Gas Code. Copies may
be obtained from The American Gas Association, 400 N Capitol
St. NW, Washington, DC 20001, www.AGA.org.

<5. Clearances Rear Sides
Combustible 6' 10'
Standard Oven Non-combustible 0' 0'
Convection Oven Non-combustible Min. 4' 0'
6. For proper combustion, install equipment on adjustable legs or
casters provided with unit.
7. For proper combustion, install equipment on adjustable legs or
casters provided with unit.
NOTE: In line with its policy to continually improve its product, Vulcan
reserves the right to change materials and specifications without
notice.
Specify type of gas when ordering.
Specify altitude when above 2,000 feet.

I don't know where you live, but most residential gas lines are only 3/4' around here. YOu'd have to be in a commercial building, or a multifamily dwelling to be able to have a 1' gas line. The manufacturer is telling you that their specs incorporate installation in accordance with NFPA recommendations, therefore those regulations become part of the manufacturer's requirements. Installing an appliance in accordance with the manufacturer's requirements is part of local building codes everywhere.

The link to the National Fire Protection Association codes dealing with restaurant venting and fire protection is provided below. Those are the minimum codes your municipality will require. You can purchase the codes for only $35. You will still be required to have a professional design and install your ventilation/fire suppression to be in compliance with the manufacturr's install provisions. Because you are residential and not commercial, you will not be able to receive a warranty on the equipment, and you may not find a professional to do this. It's a Catch-22.

http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=96


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RE: Help Figure Out Exhaust Hood And Makeup Air Needs?

I have done this in two homes. We followed all the procedures above and have never regretted our decision. I won't repeat references to codes, etc., because I agree with everything said above. However, in answer to your musing about relative cost, in my experience, the ventilation, fire suppression, make-up air, etc. systems cost about 4 to 5 times the cost of the range. Should you need roof modification, etc., that would add more. I would also add, we live in a rural area and I wanted a fire suppression system regardless of whether we went with a commercial range or not. I also have obvious fire extinguishers mounted all over the house. Besides consulting our insurer, fire department, etc., we had input from restaurant ventilation designers from the two nearest cities and an engineer who only works on this subject. We were fortunate to have someone fairly local who services both commercial and commercial-in-home systems. We also have the fire suppression system and extinguishers inspected once a year. The local gas company rep. whom we also consulted, said that the fire the only fire in his memory occurred within the duct work, in a mostly wok restaurant that had had no maintenance/cleaning done. So, grease accumulation in the duct work is the number one enemy. Another note, fire suppression systems are obvious. If you want a very refined looking kitchen, you won't get that with a commercial ventilation system. We do overnight charity fundraisers and sometimes have pro caterers and cooks, and no one seems to care about the industrial aspects of the kitchen. Nevertheless, I know this would not be attractive to most residential kitchen owners here.


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Thanks - Great Links

That is very helpful! Thanks. I'm looking at those codes online now.

On the pipe size, I've done some checking around. Some 24-inch and 36-inch commercial ranges specify 3/4'' E.g. Garland G-series. Others specify 1''. I'm not sure why the difference, beyond range size.

I was thinking - SWMBO wants to set up a pottery studio in the basement, including her kiln - so that will make fire suppression even more important. A pottery kiln gets far hotter than any range (>2000F) and is left on for many hours, usually overnight. I will have to go to some pottery sites and research what I'll need to do there. And another call to the insurance company.


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