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).
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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.
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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!”
Source: https://gardencourte.com
Categories: Kitchens
