Introduction: This and future blogs are intended to provide information to persons in the entertainment and event production industry to enhance their technical knowledge and provide a better understanding relating to many electrical aspects of equipment, wiring and safety.
Disclaimer: Although the vast majority, of the information provided, is indisputable, there are cases where some of the information is “open to interpretation”, especially in the area of the National Electrical Code (NEC).
In such cases the “final say” is up to your local “Authority Having Jurisdiction” (AHJ), usually the electrical inspector. Some of the information provided is based on the National Electrical Code (NEC), however, these requirements may be accepted as written or modified by local authorities (by law), especially in large cities.
Much of the information below are paraphrased excerpts from the NEC, and are not intended to explicate the code in its entirety. This column does not necessarily represent the opinion of the editorial board or Motion Labs and its owners.
The information below pertains to wiring types in general with a special focus on conductors and cables used in the live event industry. The purpose of the dissemination of information is not to “teach” stage personnel how to do electrical work, but rather it will provide some guidance with regard to selecting the proper wiring type for specific temporary uses and identify conductors when trouble shooting.
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Let’s start off with “Color Codes”:
We will discuss the requirements that pertain to North America. North American standards are somewhat straight forward, however European standards vary by country and effective date. European standards will not be discussed herein. The information below is based on The National Electrical Code (2014 NEC).
Line Conductors:
What is a line conductor? These conductors transmit power (electricity) from an overcurrent protective device (usually a circuit breaker or fuse) to the load. On circuits that do not require a neutral, such as 208V or 240V (we’ll discuss “neutral” later), the conductors that return current from the load, back to the electrical panel, are also considered “line conductors”.
Line conductors must be insulated, and can be any color EXCEPT: White, Green, Green with a yellow stripe, and sometimes gray. (In certain instances gray is used as a “neutral”).
It’s a standard industry practice (not code) to use black, red and blue (white neutral), for three-phase on 120/208V systems. 277/480V systems use brown, orange and yellow (gray neutral) for three-phase.
As stated, these colors are standard industry practice, but except for neutral & ground it is not a requirement to have different phase line conductors identified with different colors.
Note: The above color codes apply to “building wiring”, and not necessarily “pre-manufactured cables”.
We’ll discuss cables later.
Although not common, in some facilities, there is a three-phase electrical system referred to as a “delta high leg system”. This system has a voltage of 240V phase to phase, but only two of the phases are 120V to neutral, the third phase is 208V to neutral. In this case the “high leg” must be identified by an ORANGE conductor. Per the code, the “high-leg” should be on the “B” phase, however, there are a lot of systems out there, where this is not the case, nor is the “B” phase colored orange ….. Be careful.
This high leg is not to be used with a neutral, even if a single phase load of 208V is needed.
There are a lot of “old” systems in the field that have a neutral in a three phase high leg panel, so …
If you see a circuit breaker panel, used to supply 120V circuits, with every third breaker missing (blanked-off), this is a good indication the this is a high-leg panel.
As a side note: In my younger years (a real long time ago), I had some experience in installing standard 120V circuits (I was an electrical apprentice); the boss dropped me off, to install a 120V outlet for a background music amplifier. Well… (You know what’s coming)…. I installed the receptacle circuit on a “high leg”, and didn’t check the voltage. The amplifier was real loud (for about 10 seconds), until the smoke was released.
So…learn from my mistakes…CHECK THE VOLTAGE.
In facilities where different wiring system conductors (208V & 480V) are accessible and installed in a common enclosure, the color code used for the different systems, must be identified by signage and/or by grouping (using tie-wraps or the like). There are many systems out there that don’t have the proper markings, nor do they follow any standard color code. So, it a good idea to perform actual voltage checks before connecting any load equipment.
Neutral Conductors:
What is a neutral conductor? … The NEC defines “Neutral” as: “The conductor connected to the neutral point of a system that is intended to carry current under normal conditions.”
Another term for a neutral is a “Grounded Conductor” (not Grounding Conductor).
The NEC defines “Grounded Conductor” as: “A system or circuit conductor that is intentionally grounded”.
By definition, a Grounding conductor is NOT a circuit conductor, a grounded conductor is.
Why is it called a “grounded conductor? …. Because it’s connected to a common bus in the MAIN panel along with the grounding conductors and the connection point of the grounding electrode system.
This is the only place where the neutral and grounds are common. No additional neutral / ground connections are allowed. On 120V circuits the neutral provides a path for return current from the load back to the circuit breaker panel.
Note: A neutral / ground common connection is required on a separately derived system, such as the secondary of an isolation transformer. We’ll discuss that in-depth in a future blog, where we’ll talk in depth about transformers. These systems types can be: “Step-up”; “Step-down” or just the “Isolation” (no voltage change).
Neutral conductors must be insulated, and must be identified by an insulation color of white, gray or any color (except green) with three or more white or gray stripes.
Re-identification of Grounded Conductors (Neutrals):
Neutrals that are 6AWG and smaller must conform to the insulation color code described above.
Neutrals that are 4AWG and larger may be re-identified by the use of colored tape (white or gray). As an example, a black insulated conductor can be used and identified as a neutral by applying white or gray electrical tape, which must completely encircle the conductor. Painting the conductor is also an acceptable method of identification. This re-identification need only be done where the conductor is capable of being terminated or spliced. There is no requirement to re-identify the conductor in inaccessible places, such as in a conduit.
When is a white wire not a neutral?
When wiring methods, such as Romex (Non-Metallic Sheathed Cable), BX (Armored Cable), MC (Metal Clad Cable) and the like are used as a switch leg. In this case the white wire can be re-identified (usually by electrical tape), for use as a line conductor. Power to the switch (powered from the fixture box) must be on the re-identified white wire, and power from the switch (to the load) must be on the other line conductor (usually black). This re-identification will also apply to two conductors (+ ground) cable, when used to power circuits without a neutral.
Grounding Conductors:
What is a grounding conductor? … The NEC defines “Grounding Conductor, Equipment” (EGC) as:
“The conductive path(s) that provides a ground fault current path and connects normally non-current-carrying metal parts of equipment together and to the system grounded conductor or to the grounding electrode conductor, or both.”
Grounding conductors can be bare (no insulation), or with an insulation color of green or green with a yellow stripe. Remember, a grounding conductor is not a “circuit conductor”. Circuit conductors conduct “normal” currents; Grounding conductors only carry “abnormal” currents, such as ground faults (short circuits).
Color codes for conductors inside cables:
Cables usually have a minimum of three conductors (line, neutral and ground), however, the number of conductors varies considerably. There is no stipulation in the NEC as to the maximum number of conductors in most flexible type cables.
Conductor identification may take the form of different colors, different colors with stripes or conductor numbers imprinted on the insulation. Most of the time these number imprinted conductors have the same color for all the conductors, in addition they may have one green and/or green with yellow stripe. In some cases, all the conductors are white or gray… Don’t assume white or gray conductors are neutrals.
So …. There is no “absolute” color code or conductor identifying “standard”. Don’t assume that all equipment manufacturers and/or cable manufacturers employ the same conductor identification. When trouble shooting, it is best to do a point to point continuity check (with the power disconnected).
Cables Types:
There is a vast array of cables out there, but only a few are acceptable for use in the entertainment and live event production industry.
The NEC Article we will be focusing on is Article 520:
“Theaters, Audience Areas of Motion Picture and TV Studios Performance Areas, and Similar Locations”.
Cables described in the article vary in the number of conductors, wire gauge (AWG) and insulation types.
Some of the wiring methods described in the article pertain to “fixed” or “permanent” wiring, however we will only be discussing “temporary” and/or “portable” wiring below.
Article 520.68(A) (1) (Conductors for Portables) requires that flexible conductors (cables) for stage equipment, shall be listed extra hard usage type. What is “extra hard usage type”?
These cables are defined in NEC Article 400 (Table 400.4). The most common types used for stage use are:
S, SO, SOW, SOO, SOOW, SC, SCE, SCT and EISL. There are other acceptable types, but we will only be discussing these, since these are the most common.
What do these acronyms mean? Below is an explanation of some of the commonly used acronyms:
“S” = Service Grade, Extra Hard Usage.
“O”= Oil Resistant (outer jacket only).
“OO”= Oil resistant (Outer jacket and inner conductor insulation).
“W” (When used as a suffix) = Rated for wet locations and sunlight resistant.
“W” (When used alone) = Portable Power Cable. Type “W” is not “welding” cable, as the “W” would lead you to believe.
Note on “Welding Cable”: Welding cable’s flexibility and durability makes it attractive to use in non-welding applications. However, most welding cable is not Listed by a Nationally Recognized Testing Laboratory (NRTL) like UL, meaning it does not meet NEC requirements for fixed or portable wiring. Even UL Listed welding cable that meets UL 1276 Welding Cables, is not approved for use as fixed wiring or general use portable cord unless it carries an additional Listing.
“SC”= Stage Cable (A relatively new designation, replacing type “W”, in most cases).
Type ”S” is the minimum requirement, for multi conductor cables.
Types with “O” & “OO” are not required, but acceptable.
Types with “W” suffix are generally only required outdoors, but can be used indoors.
Refer to 2014 NEC, Table 400.4 (note 7), for more information on additional types.
Single conductor cables, such as the type used for stage feeders, that typically incorporate single pole separable connectors (“cam-loks”), must also comply with the “extra hard usage” requirements. Type “W” & “SC” complies and is typical.
Per NEC, Article 520.53(H) (2): Single conductor portable supply cables shall not be smaller than 2AWG, for line conductors; of course the AWG is based on the expected load, so it can be larger than 2AWG.
A common 400 amp single conductor cable is 4/0.
Single conductor cables are usually identified by the color of the connectors (cam-locks). These colors correspond to standard wiring practices. Typically for 120/208V systems: Black, Red and Blue for phase conductors; White for neutral; and Green for ground.
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Type “SJ” (Service Cord Junior), is rated for “hard usage” (not extra hard usage) and can be used for certain applications, such as Breakouts. Breakouts are manufactured assemblies that convert a multi-pin
(multi-circuit) connector to individual receptacles, via “SJ” cord. These are limited to 20ft, 20 amps, and must be protected from physical damage. Usually attached to a truss or support structure using tape, Velcro, tie-wraps and/or fabric cord. “SJ” type cable is not allowed to be used on the stage floor. There are additional limited conditions where “SJ” hard usage cable is permitted on stage; these are specified in Article 520.68
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Conclusion:
The opinion, expressed herein, is only a personal interpretation. Check with your local authorities for final decisions on code matters. If you’re not absolutely sure of what you’re doing consult a professional.
Motion Labs is here to help.
We encourage you to ask questions, provide constructive criticism, and suggest subjects for future blogs.
Remember some of the subject matter may be argumentative in nature. If you disagree or need clarification,
let us know.
Thanks:
Jim Herrick
About the author:
Jim Herrick, over 40 years’ experience in the electrical field. Licensed in the State of New Jersey as an Electrical Contractor (License #6748) and Electrical Inspector (License #7702). Of the 40 years’ experience, 30 of which, included work in the theatrical industry, which also included electrical equipment design for major companies in the industry.
Gaining knowledge in electricals even if you are in the entertainment field is very important. Nice blog!
Yes, we agree! Thank you for reading.