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#197065 - 11/06/10 10:59 PM Commercial Kitchen hood
Niko Offline
Member

Registered: 08/17/06
Posts: 358
Loc: Campbell, CA
I was asked to wire a commercial kitchen hood that is tied to the extinguisher. But before hooking it up i need to learn the operation, the code behind, what needs to turn ON/OFF when the lever is pulled.
Can anyone please tell me the basic operation or refer me to a site that i can learn from?

Thanks
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#197068 - 11/07/10 11:36 AM Re: Commercial Kitchen hood [Re: Niko]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6274
Loc: Brick, NJ USA
Niko:
Basically, when the fire supression system is activated, the MUA (make-up-air) (supply air) (intake air) MUST be put in an "OFF" state, and the exhaust fan MUST be "ON".

Additionally, any electrical cooking equipment under the hood must be de-energized upon activation of the fire supression system. All the gas appliances are shut down via a gas valve.

Control is thru the dry contacts on the fire supression controller and the contactors for the MUA and exhaust, ad shunt trip for electrical cooking appliances under the hood.

Code requirements are within NFPA. It's best to check with your local Fire AHJ as he/she can provide code in effect in your area.
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#197073 - 11/07/10 01:50 PM Re: Commercial Kitchen hood [Re: HotLine1]
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5035
Loc: Blue Collar Country
I disagree completely with the requirements as you explained them.

NFPA 96 is as close as you're going to get as a 'standard,' ant it does not say what you claim.

NFPA 96 does NOT require the exhause fan to operate, be shut down, or any other action for the exhaust fan.

NFPA 96 only required fresh air supplied directly to the hood to be shut down - there is no requirement for the general fresh air supply for the room to be shut down.

It's simply amazing what NFPA 96 actually says, as opposed to what various installers, fire marshals, etc. seem to think it says.

There's simply no excuse for not reading it. The proper title is: NFPA 96: Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations

Otherwise, it is required that all sources of ignition under the footprint of the hood be extinguished. This, of course, means that the lights, receptacles, etc., be killed.

It ALSO means that the gas be shut off. If the equipment uses standing pilot lights, you will also have to instal a solenoid-operated interlock to prevent the gas valve from re-opening until you are actually ready to light the pilots; simply resetting the contactor won't be enough.

Another thread on this forum has drawn attention to the few inspectors out there who object to installing your contactor in a simple 'pull can,' as opposed to using a 'control panel' with a hinged door.

There is also an alarm requirement. If there is no central-station monitored system, you will have to instal a bell that rings when the system is activated.

Keep in mind that the inspection will be by the fire marshal, rather than the usual building inspector.

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#197076 - 11/07/10 06:55 PM Re: Commercial Kitchen hood [Re: renosteinke]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6274
Loc: Brick, NJ USA
Reno:

You state: "I disagree completely with the requirements as you explained them."

And your comments of disagrement seem to apply only to the exhaust fan operation in a fire supression activation. The other items, you seem to agree with what I said, with additional embelishments. Note that I used three (3) terms for what I usually only call Make Up Air, none of which are intended to mean the 'general fresh air supply to the room'.

As I do not have any NFPA Fire Codes at my desk now, I will check the statement regarding the exhaust fan operation Monday at the office. In the event that I have provided mis-information, I will post a correction.





Edited by HotLine1 (11/07/10 07:59 PM)
Edit Reason: correct word 'is' to 'in'.
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#197078 - 11/07/10 07:42 PM Re: Commercial Kitchen hood [Re: HotLine1]
leland Offline
Member

Registered: 08/20/07
Posts: 856
Loc: Lowell area, Ma. USA
NFPA 17A Wet Chemical systems.

Yes make up air must shut down. All electricity and gas/fuel shall be shut off.

As far as the exhaust shutting down... you will be hard pressed to get a solid answer.

I may have mis-spoke.

I'm looking and nothing yet.


Edited by leland (11/07/10 07:51 PM)

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#197087 - 11/08/10 06:35 AM Re: Commercial Kitchen hood [Re: leland]
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5035
Loc: Blue Collar Country
The issue of the 'make up' air hit a button with me, because the NFPA codes are quire explicit, yet the 'common understanding' is quite different. This continues, even though NFPA 96 is pretty clear.

Clear, that is, only if you have seen hoods that had their own make-up air supplied to them. Since most hoods do not have this dedicated air supply, but draw from the kitchen in general, it is common for the kitchen air to be shut down. As I read NFPA 96, though, it's not actually required to do so.

This is more than just hair-splitting. When there is an "open" kitchen, as is often seen with the "mongolian grills' set in the eating area of restaurants (rather than back in the kitchen), there is no single unit that can be described as serving the hood; shut down one and the others will readily supply the air. While that air might 'feed the fire,' it will also help ensure that the occupants can escape.

Another detail sometimes asserted is that the exhaust fan must operate when the unit trips. Again, NFPA 96 goes to the extreme of explaining, in the text of the code itself, that there is no need for the fan to operate if all the cooking equipment has been shut off.

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#197094 - 11/08/10 12:04 PM Re: Commercial Kitchen hood [Re: renosteinke]
Niko Offline
Member

Registered: 08/17/06
Posts: 358
Loc: Campbell, CA
Thank you guys for the explanation.

So, if i understand this correctly, once the pull station is activated, the alarm (fire bell) goes ON, any source of ignition (power, gas) turns OFF, the make up air turns OFF and the exhaust may stay ON.

I will call the AHJ to see what they need.
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#197096 - 11/08/10 12:30 PM Re: Commercial Kitchen hood [Re: Niko]
ghost307 Offline
Member

Registered: 05/09/05
Posts: 752
Loc: Chicago Illinois USA
I was always told that you need to kill any sources of ignition, any fuel sources, and get the smoke out of the space as much as possible while the Fire Department is on its way to you.

But you're absolutely on the right path...check with the AHJ to find out exactly what they want to see.
Now much point in doing it twice if you don't need to.
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#197110 - 11/09/10 06:30 AM Re: Commercial Kitchen hood [Re: ghost307]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6274
Loc: Brick, NJ USA
From NFPA 17A:
2-4.3 Shutoff Devices.

2-4.3.1 Exception No. 2

Exaust fans and dampers are not required to be shut down upon system activation as the systems have been tested under both zero- and high-velocity flow conditions.

Although this does not say the exhaust must be on, it has been interperted as the exhaust must be 'on' during a supression activation.

based on this, I have to correct my initial reply above to restate from that the exhaust fan MUST be "ON", and restate that it CAN be "ON"

That all said, it has been common accepted practice that the exhaust is "ON" during activation of supression. Some opinions are to remove smoke/fumes, and expel same to the exterior.




Edited by HotLine1 (11/09/10 07:07 PM)
Edit Reason: corrected error in sentence
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#197113 - 11/09/10 12:58 PM Re: Commercial Kitchen hood [Re: HotLine1]
Tesla Offline
Member

Registered: 06/16/04
Posts: 1189
Loc: Sacramento, CA
I once buried a man-week on an ANSUL system.

It was incorrectly engineered for Safeway.

First of a kind, and the boys made a number of errors.

Anyhow, the lesson is: try and get a control panel designed for ANSUL - -factory built.

I forget the name, but at least one outfit is making them.

NO WAY can you build your own for less, adjusted for your personal learning curve.

-------

And now, their mistakes:

24V control circuit unable to supply enough power to contactors -- especially notable for MUA blower at the roof.

Hence, an auxiliary XFMR and relay were tacked on.

Improper fusing -- original design placed fuses on the return path of one phase hot-to-neutral circuits. Obviously, this is a hazard since in overload there is a 50:50 chance that the return side fuse will blow first. Non-electricians will then have an outstanding opportunity to electrocute themselves doping out why things don't work. ( On a ladder, back against the grid, hanging on to bare metal studs while poking around in the dark: sweet)

-----

To complete the picture, this control can had a complicated push-button (with interlocks) control for chef use.

But that's not all: I had a trooper who balanced his meth with Mary Jane. He became upset and decided to get even with the Man. So he took enough care and effort to cross wire a fist full of circuits feeding the hood blowers. Come power-up they'd be toast.

Unfortunately, anyone that obvious is too obvious. So I sent him on far away business -- pulling in home runs -- and personally corrected his 'craft.' Come power-up he stood aghast as EVERYTHING worked perfectly the first time. ( Even the General Foreman was stunned, he told me he'd never seen THAT happen before.)

Naturally, I congratulated bozo on his outstanding work!

Come break-time he fired up Mary like he was Chong: right in front of the GC Superintendent! The smoke was so staggering you couldn't see in!

Say, goodbye!
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Tesla

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#197218 - 11/14/10 09:37 PM Re: Commercial Kitchen hood [Re: Tesla]
fireguy Offline
Member

Registered: 02/02/06
Posts: 19
Loc: Baker City, OR 97814
First question is what code has the jurisdiction adopted, if any. IMC 506-509 does not reference NFPA 96. The OP referendes 96, the most current edition is 2008. 10.4.1 & 10.4.2 All fuel sources, except steam are to be shut off upon activation of hte suppression system. 10.4.4 Shut-off devices shall require manual reset. 10.6.2, if there is a fire alarm, the suppression system must activate the alarm. No alarm, no bells and flashing lights, unless it is a local requirement. 8.2.3.3 Exhaust fan shall contiue to operate after the suppression system has been activated, unless fan shutdown is required by a listed comoponent or by the design of hte fire suppression system. 8.3.2 Make-up air supplied internally to a hood shall be shut off.

Not in 96, but the suppression systems are tested and listed to control the fire with the exhaust fan on or off. The general consensus among fire departments is they want the exhaust fan on, to exhaust heat, smoke and combustion gasses.

Cooking equipment shut down can be done with shunt trip breakers or contactors. Normally, I see shunt trip on new work and contactors on existing wiring.


Wiring is not allowed in the duct. The exhaust fan is to be hinged to allow for cleaning of the duct. Hinging the fan means the electrician needs to use a flexible cord and enough cord to allow the fan to be hinged.

Renosteinke states:
It ALSO means that the gas be shut off. If the equipment uses standing pilot lights, you will also have to instal a solenoid-operated interlock to prevent the gas valve from re-opening until you are actually ready to light the pilots; simply resetting the contactor won't be enough.

I have not seen that requirement in 96, but it is in the IMC. Look in 507.2.1.1, at least that is where it is in the Oregon Mechanical Specialty Code, which is based upon the 2006 IMC.

The NFPA standard is much better and thorough than the ICC codes.

A read only is available below
http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=96&EditionID=282

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