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Protection from Electricity in Commercial Kitchen Installations

Nfpa code talk.

Since the release of the 2020 edition of NFPA 70®, National Electrical Code ® (NEC®), a lot of discussions have taken place around the many new or revised requirements that affect residential occupancies. Requirements like emergency disconnecting means, whole-house surge protection, and expanding GFCI requirements, to name just a few. However, I feel like while the lion’s share of attention gets placed on residential requirements, there is much more to know when it comes to commercial installations. After all, don’t commercial buildings share the same need for the safeguarding of persons and property from electrical hazards as dwelling units? According to fire report data, some of the leading causes of fire in a commercial setting involve cooking equipment, heating equipment, lighting, and other electrical equipment. All of which have a common denominator here, the use of electricity!

Let’s look at an area of a commercial building that has many of the components that cause a dangerous and potentially deadly event just lying in wait – a commercial kitchen. The NEC contains certain requirements aimed at protecting people and property from electrical dangers, but there are a few other documents that we will want to consult here as well. First, let us think about the direct danger of electrical hazards. Electrical shock remains the number one source of fatal workplace injuries due to electricity, and commercial kitchens have a host of reasons why protection from electricity must be a priority. Just about every surface in a commercial kitchen is conductive and bonded to the electrical system, either by direct contact to the equipment grounding conductor or by connection to another grounded surface such as the tile floor. Because of this, nearly any contact with an energized conductor has all the components needed for electrocution. To protect against this threat, the NEC relies on a time-tested approach that we know has a proven track record of saving lives from shock: the ground-fault circuit interrupter (GFCI).

Within a commercial kitchen, GFCI protection for personnel is going to be required on most receptacle outlets. This requirement applies to both single- and three-phase receptacles on branch circuits rated 150V to ground or less. On single-phase branch circuits, this applies to all receptacles up to 50A, and on three-phase circuits, the cut-off is 100A. There is also a requirement to protect certain appliances regardless of whether they are cord-and-plug connected. Dishwashers, vending machines, and drinking water coolers/bottle fill stations must all be GFCI protected when they are installed on branch circuits that are 150V to ground or less and that are 60A or less. New for the 2020 NEC is that they have also clarified that this protection is needed in areas that might only be used for food prep and don’t have the necessary cooking provisions to deem them a kitchen. Yet, they still have all of the same potential for electrical tragedy.

Another area of great concern in a commercial kitchen is the exhaust hood over major cooking appliances. It is this hood that keeps the smoke and fumes produced during the cooking process from entering the rest of the restaurant or whatever the building happens to be. There are also many other considerations that come along with this equipment that we must be aware of. Cooking equipment is a leading cause of fire in a commercial setting, so it stands to reason that there is a significant fire protection component to a commercial cooking hood. However, while the equipment needed to operate a kitchen hood might involve complex coordination, the premise is simple. The exhaust hood will pull a certain volume of air, smoke, and fumes out of the kitchen while running, and if the volume is large enough, this might require the use of a make-up air unit to pump fresh air back in. There will most likely be some form of automatic fire extinguishing system under the hood that is effective on grease fires. Lastly, any lighting within the hood must be able to withstand high heat and be easily wiped down to prevent a build-up of excess grease, which could potentially lead to grease fires if not kept in check.

The NEC contains many of the requirements to ensure that the electrical system does not contribute to kitchen fires when it comes to these exhaust hoods. However, we also need to look in NFPA 96, Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations , which deals with ventilation control and fire protection of commercial cooking operations. This standard covers exactly how this system is intended to operate, both to minimize the fire hazard and to maximize the effort to extinguish any fire that might occur. This includes requirements for how the hood system will function, but it also contains requirements that the electrical system installer needs to know about as well. Chapter 9 contains sections that discuss what type of electrical equipment is permitted to be installed within these systems. Items like luminaires, motors, and other electrical devices are generally not permitted to be installed within hoods or in the direct path of travel for exhaust products. However, if this equipment is listed for this purpose, then it is acceptable. This means that any light, motor, sensor, switch, or other pieces of the electrical system of a hood must be specifically designed to handle the environment to which it will be exposed. The main thing here is that we don’t want the electrical system to be the cause of a grease fire within a kitchen exhaust hood.

In addition to requiring special light fixtures and motors for hood systems, there is another major component to the functionality of the associated equipment that we must be aware of. In the event of a fire, one that would activate the extinguishing system (not the kind from the fancy chefs as they flambé your steak), a few things need to happen. First, a fire needs fuel and air to burn, so when the extinguishing system is activated, it must be set up to immediately turn off all sources of fuel and electrical power that produces heat to all the cooking equipment under the protection of the hood. This means, most likely, the use of shunt-trip devices supplying the affected circuits. After all, no need to continue pumping heat into the fire that the system is trying to put out. Also, if there is a make-up air system, upon activation of the extinguishing system, the supply air must also shut down, and the exhaust must automatically ramp up to maximum capacity. This robs the oxygen from the fire to help maximize the effectiveness of the extinguishing efforts. This is usually accomplished within the programming of the kitchen hood control system. However, as an electrical contractor, I was often called in to work on kitchen equipment that was modified or added by individuals who were unaware of these requirements. Unfortunately, these kitchens were disasters waiting to happen.

Next time you find yourself enjoying a good meal at your favorite restaurant with the ones you love, take a minute to appreciate all the components that go into protecting them from the dangers lurking behind those swinging doors. It takes a lot of effort, planning, and execution to ensure that our night out on the town stays safe. Coordination between all trades involved in a kitchen is paramount for safe installations and the key to working together to achieve a safe environment. It’s like the mantra of NFPA says, “It’s a big world. Let’s protect it together!”

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A Primer on UL-Listed Kitchen Ventilation

Understanding the basics of certain key features is essential to proper design.

The kitchen is often a key area in a commercial facility, and proper ventilation of this area is critical. In this article, I want to focus on the three facets of ventilation design I consider most important: commercial kitchen hoods, fire-suppression options and pre-manufactured raceways.

Commercial Kitchen Hoods

Why should one investigate the use of a UL 710-listed hood?

The International Mechanical Code Chapter 507, “Commercial Kitchen Hoods,” makes exceptions to the Code’s requirements for commercial kitchen hoods for construction and exhaust CFM level designs for listed and labeled UL 710 hoods. The main function of the UL 710 test is for safety of the hood during a fire condition. The test procedure makes sure that, during a fire condition, the hood is liquid tight and does not allow the grease to migrate through any of the joints or seams, which would allow for the fire to follow the same path and spread outside of the hood canopy.

Utility raceway utilizing horizontal and vertical pedestals to mount pot-filler faucets.

During the fire condition, the test also monitors the temperature of all electrical components in the hood to make sure they do not exceed their temperature ratings during a fire condition. The UL 710 test also has a visual smoke capture test to verify the minimum exhaust flows that the hood will capture smoke at during the cooking process for different cooking surface temperatures.

It is important to remember that the visual smoke capture test is conducted by the laboratory technician’s eyes. It is also important to note that the test is conducted in a laboratory condition and the room is balanced to a .-02” SP. Because it is a controlled environment, the test laboratory’s conditions are not realistic for what is found in a real-life condition in a kitchen or servery. The exhaust volumes needed for capture and containment in real life conditions may be 10% to 200% higher than the listing values needed for complete capture and containment of the smoke, grease-laden vapors, and convection heat produced by the cooking process.

In recent years, the performance test used and accepted by the kitchen ventilation industry to show how well a hood captures is the ASTM 1704-05, Standard Test Method for Capture and Containment Performance of Commercial Kitchen Ventilation Systems . The performance reports for most major hood manufacturers are published at the Food Service Technology Center’s Web site, www.fishnick.com . The ASTM 1704-05 test utilizes a Schering camera to be able to visually see the heat produced by the cooking appliance and if it is captured by the exhaust hood. There are five types of UL-listed hoods:

Baffle filter type , which utilizes standard baffle filters with a grease extraction rating of approximately 28% for 8 microns and larger particulates. This type of hood has the lowest entry cost, but also gives the lowest grease extraction of particulate of the available hoods.

High-efficiency extractor type , which utilizes high-efficiency grease extractor filters with a grease extraction rating of approximately 90%+ for 8 microns and larger particulates. This type of hood has a mid-level entry cost, but also gives the highest grease extraction of the available hoods.

Self-cleaning water wash hoods with stationary filtration ,  which have a grease extraction rating of approximately 60% for 8 microns and larger particulates. This type of hood has a mid high-level entry cost but is the easiest to maintain.

High-efficiency extractor type , which utilizes high-efficiency grease extractor filters and UVC lights with a grease extraction rating of approximately 90%+ for 8 microns and larger particulates. This type of hood has a high-level entry cost, but with proper maintenance will keep the exhaust ducts beyond the hood virtually grease-free.

Self-cleaning water wash hoods with stationary filtration and UVC lights , which have a grease extraction rating of approximately 90%+ for 8 microns and larger particulates. The hood has a self-cleaning feature that cleans the stationary filtration system and the UVC lights in the exhaust plenum daily. This type of hood has the highest-level entry cost, but is the easiest to maintain; just a little maintenance will keep the exhaust ducts beyond the hood virtually grease-free.

Versatile Utility Distribution System (UDS) and hood with fire protection during an installation. Photos courtesy of Professional Foodservice Design, Inc.

Fire Suppression Options

The kitchen exhaust hood fire suppression system is the first defense against fire in a commercial kitchen. Let’s take a quick look at four options for suppression systems under the hood. Appliance specific systems. These cost less and target specific equipment in a fixed location. They allow the offending piece of equipment to be doused with a wet chemical, by an appliance-specific nozzle, to extinguish fire and cool down the equipment and reduce the potential for re-ignition.

Full flood/overlapping systems. These are typically more costly than appliance-specific systems and have a much larger reservoir of chemical, which provides a virtual zone of protection under the hood by overlapping wet chemical dispersion coupled with fusible link detection. They allow the flexibility of a full flood system because equipment can be moved in and out for cleaning and exchanged with other equipment as desired. For this reason, it is the system of choice for many food establishments.

Dual agent systems. These typically use a combination of a quick-acting liquid chemical (to extinguish) and water (to cool down the area and diminish the chance of re-ignition). In some cases, the water enhances the characteristics of the liquid chemical used to extinguish the fire.

Water mist. NFPA 96 (1998 edition) Chapter 7, “Fire Extinguishing Equipment,” addresses the use of water mist fire protection. Notes Section 7-2.2.1, “Automatic fire extinguishing systems shall be installed in accordance with the terms of their listings, the manufacturer’s instructions, and the following standards where applicable, (b) NFPA 13 Standard for Installation of Sprinkler System .” The NFPA 13 4-9.8.2 (1999 edition) or 3-9.8.2 (1996 edition) say the same thing: “A sprinkler or automatic spray nozzle used for the protection of a deep fat fryer, shall be listed for that application. The position, arrangement, location, and water supply for each sprinkler or spray nozzle shall be in accordance with its listing.”

The Dualtech nozzle is UL 199E-listed for use over fryers. The UL 199E testing follows the same criteria as UL 300, except it is more stringent since it actually requires a kitchen hood to be mounted over the appliance during the test, whereas UL 300 does not.

Please note that manual activation is not required for an automatic sprinkler system, per NFPA 96 (1998), sections 7-5.1 Manual Activation, Exception #2.

NFPA 13 (1999) 4-9.3 and NFPA 13 (1996) 3-9.3, say the same thing as Exception #2: sprinklers or automatic spray nozzles shall not be required where the entire exhaust duct is connected to a listed exhaust hood incorporating a specific duct collar and sprinkler (or automatic spray nozzle) assembly investigated for protection of unlimited duct length of duct in accordance with UL 300, Standard for Fire Extinguishing System for Protection of Restaurant Cooking Areas . The EA-1-1/4” orifice and 65-degree angle of discharge has been UL tested to standard UL 300 for the protection’s unlimited length of duct and listed for this purpose when used with listed mist systems.

NFPA 96 (1998) accepts listed hoods, per Section 2-4, Listed Hood Assemblies. “Listed hood assemblies shall be installed in accordance with the terms of their listing and the manufacturer’s instructions.” The UV hood is UL 710-listed, therefore it is accepted by NFPA 96 (1998).

UL attachments to the building sprinkler system have faced much adversity since UL 300. Other than very specific open fryers listed for coverage by a Dualtech nozzle, open fryers can no longer be protected by mist systems.

At this time, the chemical systems seem to be more design friendly to this problem.

Pre-Manufactured Raceways

When four or more pieces of equipment are placed under a ventilator, it makes great sense from an engineering and economic point of view to have a factory-built raceway as an accessory to your UL-listed hood. The raceway’s cost will approximate the costs of supplying and installing all necessary components into the building to tie together the power sources and fire protection.

Pre-manufactured raceways are considered to be pieces of equipment with a seven-year depreciation schedule in lieu of a 32-year leasehold improvement building depreciation when utilities are built into a wall. The raceway can be custom designed by a food facility consultant or others with an encompassing perspective on the use and needs of both the equipment and the staff using it.

Flexibility in supplying gas, electric, steam or water is the mantra of a distribution system. Systems vary by manufacturer and patent in how supply and connection are accomplished to each piece of under hood equipment. The end result is minimal expense or effort in moving equipment around under your hood.

The raceway will come complete with a minimum of the following accessories, with others being available by request.

Gas hoses w/quick disconnect

Water hoses

Power cords and plugs

Power supply

Pressure gauges

Ball valves for plumbing lines

Main disconnect w/shunt trip

Water metering

Fire protection tie-in.

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Commercial Kitchen Hood

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Ok so I got thrown into doing this kitchen hood. Not much info given. Basically I have a exhaust fan, make up air, and lights. Doing research on here I have figured basically everything needs to shut off except the exhaust...which could also depend on local requirements. Now my question is how exactly are the make up air and exhaust supposed to be controlled? Basically is it just a on/off PB on the wall that enables both units for normal operation? I can figure out the controlling to be inter connected with the fire suppression without much problems I am just actually unsure of the normal operation side of it.....never done one before. Also I have noticed you guys talk about using shunt trip breakers to kill power to make up air, lights etc, but could I just achieve the same results with contactors....or are the shunt trips needed?  

I've seen it done with shunt trips as well as with contactors. Shunt trips are great for it. You would just run your shunt circuit through the contact in the fire suppression control box and if it triggered, it would trip all the breakers. Regarding the exhaust fan, typically (as I understand) the exhaust needs to stay on if it's already running, or it needs to turn on if it's NOT running. To achieve that you could put in a contactor controlled by a contact in the fire suppression box and just run a loop parallel to whatever switch turns the fan on normally.  

The MAU should come with a control panel. You will have to install contactors for the exhaust fans. You will have control wiring from the fire suppression, to the control panel. And the control panel will operate the contactors. Don't use shunt trips.  

Here you just need to kill the makeup air. Use a microswitch in the suppression box. Can't have positive pressure in a fire. It is also required to interlock the exhaust fan to the makeup air so it won't run without the exhaust fan.  

farlsincharge said: It is also required to interlock the exhaust fan to the makeup air so it won't run without the exhaust fan. Click to expand...

Microswitch in the ansul panel operates no and nc contacts in the hood panel. Here we have to kill mau and all underhood electric including lights so I run mau and all underhood electrics on a small subpanel backfed with a two pole shunt trip breaker. Saves a buck that way.  

Ok so this job is becoming more and more of a headache. The MAU is not in yet but they need the wiring run now to a JB by the location as the ducting is running through a separate tenant space and they can't have the other tenant shut down too long(don't ask). Is there any control wiring typically needed to go up to the MAU or is it just straight feeds and all the controls are done in the kitchen.  

CanadianSparky said: Ok so this job is becoming more and more of a headache. The MAU is not in yet but they need the wiring run now to a JB by the location as the ducting is running through a separate tenant space and they can't have the other tenant shut down too long(don't ask). Is there any control wiring typically needed to go up to the MAU or is it just straight feeds and all the controls are done in the kitchen. Click to expand...

Most the new installs now just need a constant feed to the control panel, the on/off switch and temp sensor are wiref low voltage in parallel. Anything electric under hood and make up air shuts down during ansul op. What u can do is drag a feed from ex fan leg, make/break at ansul and feed contactor( s) feeding said items.  

It is looking like All the controls will be done myself. They seem to have an ansul system with just a set of NO and NC contacts...None of the contacts will be able to handle the loads of any of the equipment. This is the equipment that was order....Don't ask me why but not my problem Exhaust fan(120v 20.8fla) :no: Make up air(specs are kinda up in the air because no one has answers but it is a 208 3ph) Hood lights Gas valve (no one has the answer if it is mechanical or electrical) Now I have never wired up a make-up air unit before and not sure what it comes with control wise as I can't get any specs or info on that either. Basically I have the feeds for exhaust and MAU ran up to where the units will be as we had to have this done because the ducting and wiring runs through another tenants space an they have basically been booted out until the ducting is done. Do the MAU typically have control wiring running up to the unit or is it all done in the kitchen. I plan on controlling the MAU, lights, valves, and exhaust all through a series or contractors which will be tied into the Ansul system.  

Your in Canada so it may not apply but in the US an updraft hood exhaust has to be mounted with a hinge for NFPA. This means a whip with some slack so the fan can be tilted back for service. NFPA Fire Code #96: 7.8.2.1 “Rooftop terminations shall be arranged with or provided with the following: (8) A hinged upblast fan supplied with flexible weatherproof electrical cable and service hold-open retainer to permit inspection and cleaning that is listed for commercial cooking equipment..” NFPA Fire Code #96: 8.1.1.1 “Approved upblast fans with motors surrounded by the airstream shall be hinged, supplied with flexible weatherproof electrical cable and service hold-open retainers, and listed for this use. Hawkrod  

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