One of the most important aspects of electrical safety that does not get enough attention is labeling. Labeling is ultimately what allows employees to avoid danger and understand exactly what it is that they are using. It is also what provides people with important electrical information. Imagine the chaos that would ensue if we always had to guess whether we were putting our safety at risk or not.
Putting aside the practical reasons mentioned above, electrical labeling is also important because it is a mandatory part of OSHA’s rules on electrical safety. According to OSHA 1910.335(b)(1): “Safety signs, safety symbols, or accident prevention tags shall be used where necessary to warn employees about electrical hazards which may endanger them, as required by 1910.145.” Like it or not, you will be subjected to onsite OSHA inspections. Over time, the rules have gotten far stricter. Penalties for disobeying key rules are as harsh as they have ever been.
One of the most common errors that people make in passing an OSHA inspection is the lack of proper electrical labeling. This leads to fines and even more inspections down the road.
In this comprehensive guide, labeling requirements will be discussed for equipment that is usually found in most industrial buildings. You might not find your piece of equipment here, and, if that’s the case, we will provide a resource at the very end to assist you. The one piece of equipment that you don’t think the inspectors will check for labeling will probably end up being the one that gets you in trouble.
It is also worth noting that you might finish reading this guide with more questions than answers. Even with the information presented, you might not be completely confident in taking the initiative to label your equipment properly. If this is the case for you, contact a licensed professional that is qualified to guide you through the process. They will inspect your current labeling and tell you where changes need to be made.
Let’s begin by looking at the cable tray—the electrical utility where power is coming in from. It has to be marked with the wording “Service-Entrance Conductors” (2011 NEC, 230.44). Next, the service disconnect needs to be labeled as “Service Disconnect” (NEC 230.70(B)). On that service disconnect, you also need to have the amps interrupting capacity (AIC) displayed and field marked (NEC 110.24(A)) and the voltage. The number corresponding to the AIC will represent the maximum fault current that the breaker can safely interrupt without undergoing self-destruction.
Most buildings have one service disconnect, but some of them have more than one. According to NEC 230.72(A), if you have another service disconnect, you have to label it as such while providing another label that clearly states where the other disconnect is located. This is useful for emergency situations where all of the power needs to be shut down. Finally, NEC 110.34(C) requires you to put up a sign reading “Danger – High Voltage Keep Out” on the entrance of a locked room if it contains service equipment.
Don’t forget to follow ANSI Z535 when you are designing your labels—the color of your text and background matters!
Next, it is time to examine the control centers and distribution panels. NEC 110.22(B-C) states that control panels corresponding to series-rated overcurrent devices must have the series combination ratings clearly labeled and field marked. These ratings related to the AIC rating, which must be included as part of NEC 110.24(A).
The manufacturer of the breaker will usually include a number that represents the minimum current that a breaker can tolerate before a trip occurs. As a brief reminder, make sure that if you replace any of the breakers in the panel, you must use a replacement of the exact same size. This is a very common OSHA violation that is discovered upon investigation.
You should also know about NEC 110.16 and NFPA 70E—these are very strict rules that require everything to have an arc flash label attached. This label will include information such as the hazard risk category, the necessary level of personal protection equipment, minimum arc rating of the clothing, and so on.
Make sure that the equipment has ample room for employees to work with, while providing easy access to live parts. This is part of NEC 110.34, which also states that the minimum distance for the working space must be indicated.
Before you open a panel or switchboard, you will probably notice a warning label on the front cover that states you should not operate on it while carrying current (NEC 225.70(2)). The only exception to this rule is if the equipment is interlocked in such a way that it cannot operate under load. When in doubt, shut down all power before working on the panel or switchboard.
NEC 408.4(A) states that every circuit within the panel must be clearly identified with respect to its purpose and easily distinguishable from every other circuit in the panel. You must also mark your panel wiring with color-coded labels (NEC 210.5(C)(3)) and provide accessible documentation that clearly states what each color represents (NEC 408.3(E), NEC 409.102(B)). This information must also be permanently posted on the panel’s outside cover.
The phase-to-ground voltage must be labeled correctly to avoid damaging equipment through the incorrect wiring of equipment. Certain systems are assigned a color scheme according to NEC, depending on the high leg. NEC 408.3(F)(1) states that you must mark the phase that is going to the ground along with its associated voltage.
If you have any transfer switches that transfers power from the electric utility to a generator that serves as an alternate way of providing energy to the electrical panels, NEC 700.10(A) states that you must label the switch as “Emergency System” using a red background and white font.
In addition to this, you need a warning label that states a shock hazard could happen with the grounding electrode conductor while the alternate energy sources are being powered (NEC 700.7(B) and NEC 701.7). Finally, don’t forget that orange voltage markers must be applied to this equipment.
We now move on to labeling industrial control panels. The labeling requirements are generally the same as previously outlined for panelboards and switchboards, with additional rules for proper installation. Usually, several items are included within these control panels. To account for this, it is required that the lowest-rated short circuit current rating is used to mark the panel. However, an overall high-fault rating requires an additional label that reads similar to the following:
“WARNING: RISK OF FIRE OR ELECTRIC SHOCK. The opening of the branch circuit protective device may be an indication that a fault current has been interrupted. All current-carrying parts and other components should be examined and replaced if damaged. If burnout of a current element of an overload relay occurs, the complete overload must be replaced.”
NEC 409.110(1-3) is important because it states that panels that have more than one power source connected to them must have every source clearly labeled, with an additional indication that all of them need to be disconnected to fully power down the panel. NEC 480.4(A) also stated that every component—conductors, wiring, etc.—must be clearly labeled. This sounds like nitpicking, but it comes in handy when it is time to make repairs.
For disconnects and breakers, you must put up warning signs not to replace fuses while the circuit is operating on anything that is 600V or higher and place them next to the fuse (NEC 227.50(3)). This rule does not apply for lower voltage equipment because there is usually a mechanism in place to shut down power automatically if someone tries to gain access to the fuses.
Finally, we have industrial automation equipment. The most important thing to remember here is that every button and switch must be clearly marked and labeled with its specific purpose and/or function. It is also required that you have the necessary safety warnings and instructions attached to each component (NFPA 70E). This is also covered by OSHA 1910.145(e)(2):
“The wording of any sign should be easily read and concise. The sign should contain sufficient information and be easily understood. The wording should make a positive, rather than negative, suggestion and should be accurate in fact.”
There are also specific rules that pertain to minutiae details of the sign—sizing of the titles relative to the body of the text, the color of the background, and the font to be used depending on the context of the situation, borders, symbols required, and so on. This is entirely dependent on your industry and its regulations, so you will have to find this information yourself.
One last point to note is that any sign and label should obviously be kept in good condition and not be worn out. NFPA 70E, Sec. 205.11 requires that all warning signs must be easy to find, securely attached to the equipment condition, and maintained in a condition where the text is legible.
Do not get complacent with labeling—it is easy to look at pre-existing examples in your field and assume that you can get away with doing the same. Always look at the codes from the original source to see the exact rules that apply to you and your industry. It only takes one small mistake with labeling to jeopardize the safety of yourself and everyone else in your building. Even if safety is not put at risk, you open up the possibility of repairs and maintenance that take up a lot of time and were not necessary to begin with.
Whenever you purchase a product from a trusted supplier, it will usually come with its own labels and safety warnings. However, this will not be enough. OSHA, NEC, NFPA, and NASI rules, regulations, and standards will usually require that you tack on additional labels to clearly indicate important information and safety guidelines that must be followed.
If you want to learn more about proper electrical labeling, this comprehensive white book does a great job of listing the labeling and inspection standards that commonly used electrical equipment has to meet. It is rather long and technical in scope, so use it as a handy reference guide whenever you need it.
