The National Electrical Code (NEC) is a national standard authored and published by the National Fire Protection Agency (NFPA 70). This standard is adopted as regulation in all 50 states and is the benchmark for safe electrical design, installation, and inspection to protect people and property from electrical hazards.
Budget Impact
The 2017 edition of the NEC has introduced some new labeling requirements for Industrial Machinery control panels that companies should be aware of. While a new label may seem very innocuous at first glance, this one may have an unexpected budget impact.
While most people think of the NEC as it applies to the power distribution in their homes, commercial buildings, or industrial plants, in many areas it also delves into more detail. One of these areas is the requirements for the installation of Industrial Machinery (Article 670), including control panels found in food processing, chemical processing, or anywhere qualifying as industrial.
Why Important
Why is this important to any industrial environment? With the new labeling requirement, companies will be required (by law/regulation) to have that information on equipment in any jurisdiction where the 2017 Edition of the NEC has been adopted. Facilities that don't have the information to provide this required labeling will have to engage someone to perform the proper system analysis to obtain the necessary data for the labeling. If this analysis is needed, it can be expensive. We have heard estimates that can be as high as $20K+ per plant. The need for this analysis may vary depending on the size of the company as larger facilities may already have completed the study for arc flash purposes. However, smaller companies historically haven’t yet done this so there can be a significant impact. Since the new labeling is expected to be grandfathered in, the actual impact (requirement) may occur when an upgrade or change is made to the company’s equipment that necessitates the labeling upgrade.
Terms Defined
Before we delve into the changes, however, we need to define a few terms that will allow us to understand the subject a little better.
Short Circuit: This is a condition in which a live energized wire or part comes into contact with another live energized wire or part (known as a phase-to-phase fault) or a grounded wire or part (known as a phase-to-ground fault). In these instances, the normal resistance to current flow is removed, and the amperage flowing instantaneously spikes to enormous values until interrupted. In an industrial environment, these levels are generally in the thousands of amps and, if unmitigated, can cause fires, arc flashes/blasts, etc.
Maximum Available Short Circuit Current: This is a calculated value (usually expressed in kA – thousands of amps), and represents the maximum amperage that can be delivered at a given point in the power distribution system during a short circuit event. Calculating this value takes into account everything from the transformer supplying the plant from the electrical utility to the size of the wire supplying the control panel and, quite literally, everything in between. Obtaining these values is done easiest by the designer of the power distribution system during the design process. However, if you have an older facility and don’t have that information, there are companies out there that specialize in providing this data – for a fee, of course.
Short Circuit Current Rating (SCCR): This is a value (usually expressed in kA – thousands of amps) calculated by the designer of the control panel in question. This number represents the maximum fault current to which a control panel can be connected. It does NOT represent the amount of amps that are capable of flowing through the panel during a short circuit.
The NEC has included the following paragraph since the 2011 edition:
670.5(1) Industrial machinery shall not be installed where the available short-circuit current exceeds its short-circuit current rating as marked in accordance with 670.3(A)(4).
Paragraph 670.3(A)(4) says that the required permanent nameplate for the control panel must include:
(4) Short-circuit current rating of the machine industrial control panel based on one of the following:
a. Short-circuit current rating of a listed and labeled machine control enclosure or assembly
b. Short-circuit current rating established utilizing an approved method
So, what do we know so far? First, the control panel must be marked with its SCCR. Secondly, it cannot be installed unless its SCCR is equal to or greater than the available short-circuit current of the power distribution system it’s being connected to.
So, what’s missing? What’s new? Well, let’s look at this from an electrical code inspector’s perspective. What information does he need to give you the stamp of approval? Well, the SCCR…. yes, there it is right there. What else? The inspector still needs the available short-circuit current. Does he/she guess? Assume a “typical” value? Since 2011, that’s where we were at.
Well, in 2017, the NEC took care of that by including a new paragraph:
670.5(2) Industrial machinery shall be legibly marked in the field with the maximum available shortcircuit current. The field marking(s) shall include the date the short-circuit current calculation was performed and be of sufficient durability to withstand the environment involved.
So, now the code inspector has something to work with. He/she knows both the SCCR and available short circuit current. A quick comparison and you get the stamp of approval…. or a denial. It’s that simple. The question now becomes, do you have that information? If you’ve got a new facility, odds are you do, and you’re all set. Maybe you’ve been doing an arc flash hazard analysis which requires that information as well. Great – you’re all set. However, if you don’t have the data, the choice as to whether or when to spend the money to have that analysis done is being taken out of your hands. If your plant is in a jurisdiction that has adopted the 2017 NEC as regulation (and it will sooner or later), you MUST have that analysis done in order to be code compliant when installing any new equipment.
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