Typical Temporary Power Distribution For Live Entertainment

By: Jim Herrick

Introduction: This blog is intended to provide information to persons in the live entertainment 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 2014 National Electrical Code (NEC), however, these requirements may be accepted as written or modified by local authorities (by law), especially in large cities. This information does not necessarily represent the opinion of the editorial board or Motion Labs and its owners.

The National Electrical Code (NEC) outlines and defines the requirements for the permanent and temporary power distribution equipment installation for live entertainment.

The NEC articles that relate to these types installations are described in the following:

  • (518) Assembly Occupancies;
  • (520) Theaters, Audience Areas of Motion Picture and TV Studios Performance Areas, and Similar Locations;
  • (525) Carnivals, Circuses, Fairs and Similar Events;
  • (530) Motion Picture and TV Studios and Similar Locations.

We will be mainly focusing on “temporary” installations in “Theaters, Audience Areas of Motion Picture and TV Studios Performance Areas, and Similar Locations” (NEC Article 520). Keep in mind that there are other articles in the code that may apply, but if your equipment and installation methods conform to the parameters described in Article 520, that’s the code article you should comply with. In cases where Article 520 is moot on any subject or equipment you will be installing, you may have to revert to the “general sections” of the code, described in Chapters 1 through 4, these chapters pertain mostly to permanent installations however.

It is absolutely necessary that you know what the connected load (amps) will be. That’s up to you to figure-out before starting any power distribution system design. We will not be discussing these requirements herein.

For the sake of clarity, we will arbitrarily break-down these temporary (portable) systems into three sizes:

  • Small: 20 to 50 amps, single phase.
  • Medium: More than 50 amps, up to 200 amps, single & three phase.
  • Large: 200 to 400 amps (or more), three phase.

One of the limiting factors, pertaining to system size, is the type of connection method you will use to connect your temporary power distribution system (PD) to “house power”. It can be as simple as a 15 amp Edison plug up to 400 AMP “Cam-Locks” (in some cases multiple Cam-Lock sets).

The power distribution systems we will be discussing, will most likely fit somewhere in between the two scenarios depicted below (but you never know, so be prepared):

Real small:
small power distribution systems

Real Big:large power distribution systems

Small size systems:

The “smallest system” may only consist of a 15A “power strip”, and a couple of extension cords. As simple as it is, it’s very common, and is typical for a three or four-piece band with no stage lighting and a minimal sound system. There is no need to go into any more detail …. Let’s move on to a little larger system:

As previously stated, the connection method to “house power” is the first thing to consider. Small Power Distribution Systems (PD) usually incorporate 30A or 50A plugs on the input. There are various configurations, however, most typical are: (2) Line conductors, (1) Neutral conductor and (1) Grounding conductor.

The common designation is: 125/250V, XXA, 4 wire. The voltage designation is the “maximum” voltage allowed for use with these connectors, although the actual voltage will typically be 120/240V.

Since most (if not all) the connected load will be 120 volts, these arrangements will supply 60 amps @ 120V on a 30-amp connector and 100 amps @ 120V on a 50-amp connector. Another thing to check is whether the receptacle configuration is “Twist-Lock” or “Straight Blade” (provided by the “house”).

30A Twist-Lock

30A Straight Blade

50A Twist-Lock
50a Twist-Lock

50A Straight-Blade
50a Straight Blade


The next thing to do, after the determination of the input connector, is to figure-out the quantity and type of receptacles you require for your load equipment and the location, on stage, of these receptacles. The cord coming from the house receptacle is typically connected to a “breakered stringer box”, which breaks-out the 30A or 50A power into several 120V, 20A outlets. Most of the time, these outlets are NEMA 5-20R, but can be “Neutrik Power-Cons”, “Twist-Locks”, “Stage Pin Connectors”, or whatever you require.

These breakered stringer boxes always have an input connector (usually Twist-Lock), and may also have an output connector (feed through), which enables several units to be “daisy-chained”. When converting 30A or 50A to 20A (to feed 20A receptacles) a circuit breaker is required, which is integral in the “Breakered Stringer Box”. Several of these boxes may be fed from separate outputs on the main power distribution unit.

If a reduction in the ampere rating of connected devices is not required, a “Non-Breakered Stringer Box(s)” is all that’s needed. These units may take the form of a single box or several outlet boxes mounted “in-line” on a single cord (depicted below). These cord-mounted box assemblies allow placement of receptacles where you need the power, and eliminate the need for additional extension cords.

Breakered Stringer Box
Breakered Stringer Box

Single In-Line Box
Single In-line Box

Multiple Boxes on a Single Cord
Multiple Boxes on a Single Cord

Medium Size Systems:

50A to 200A systems can be single phase or three phase. Power distribution equipment can be manufactured to specifically operate on either system. This does not exclude the use of a single phase system on 3-phase, or a 3-phase system on single phase. When this is done, however, it does not use the PD equipment to its full capacity or may not use all the house power that may be available.

Single Phase (Grounding conductor not shown)
Single Phase

Three Phase (Grounding conductor not shown)
Three Phase


There are several types of system components that may be used for medium sized systems. The selection and quantity of these components vary and are dependent on your requirements.

Cam-Lock type, single conductor, separable connectors and cables are the most common type of main feed input connection. Cable sets can be manufactured in any length. Pin & Sleeve connectors are available, but are less common.


Cam-Lock Connectors
Cam Lock Connectors


Cam-Lock Cable Sets
Cam-Lock Cable Sets


Pin & Sleeve
Pin & Sleeve


Connection to house power may take the form of mating Cam-Lock connectors on a “company switch”, or may be directly hard-wired to a circuit breaker panel or disconnect switch.


Company Switch
Company Switch


Circuit Breaker Panel
Circuit Breaker Panel


Disconnect Switch
Disconnect Switch


Main Power Distribution Units (medium size)
Main Power Distribution Units (medium size)
Main Power Distribution Units (medium size)
Main Power Distribution Units (medium size)

Satellite Branch Circuit Power Equipment (fed from the main PD)

Breakered Stringer Box
Breakered Stringer Box


Multiple Boxes on a Single Cord
Multiple Boxes on a Single Cord

Rack-mounted PD
Rack-mounted PD

Large Size Systems:

These systems are generally 400A, (or more), 3-phase. Larger systems may require multiple 400A units. Output Cam-Lock connectors (feed through) can be provided to allow several PDUs to be daisy chained together. If more than 400A is required, several 400A units may be fed by individual 400A feeder circuits.

There is a vast variety of “sub-main” and “satellite” power units that may be selected to distribute power to different portions of the stage area; these areas may include: center stage band gear, front of house mixers, lighting control consoles, stage lighting & dimmers, chain hoists & controllers, special effects, powered speakers, monitor mix station, amplifier racks, and the like. The power equipment and associated cable assemblies should be selected to put power where you need it and must have the capacity to handle the electrical requirements, with some “head room”. The main PDU (depicted below) is only an example. There are multiple power output devices (outlets) the can be incorporated, in both type and quantity.

400A Main Power Distribution Unit
400A Main Power Distribution Unit



Amplifier Racks
Amplifier Racks


Front of House Equipment
Front of house equipment


Stage Lighting Truss Hoist
Stage lighting truss hoist


Stage Lighting Dimmer Racks
Stage lighting dimmer racks


Center Stage Equipment
Center stage equipment


Unfortunately, there is no “one size fits all”. Each job will have different requirements.
Consideration should be given to the “modularity” of your system. You can start small and add equipment as expanding requirements present themselves. As an example, what was your 100A main system, may become a satellite for a new 400A system. Conversely, the 100A “sub-main” portion of your 400A system may become the “main” for a smaller job.

There is no way of describing all the possible scenarios that you may encounter, and configurations that may be required. There are literally hundreds of Power Distro configurations available and an infinite number of potential job requirements. Check-out Motion Labs web-site to view a multitude of possible options. www.motionlabs.com

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.

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.

7 responses to “Typical Temporary Power Distribution For Live Entertainment”

  1. Really what a awesome article on the ideas for the typical temporary power distribution for the live entertainment. They are must read for many. This article is a good one to look at. I like how you have researched and presented these exact points so clearly.

  2. Roger White says:

    Thank you for the informative article: I’m in the process of creating an outdoor venue on the Colorado plains. The information you have disseminated has been very useful and I will share it with my electricians. Any other knowledge you can put forth will be much appreciated. Again, thanks. Roger

  3. Roger White says:

    Thank you for the great article

  4. Wil says:

    Can you explain this, please? I’d like to make sure I am understanding correctly that if you are on 120V power from a 30amp circuit, you can pull up to 60 amps from the distro?
    “Since most (if not all) the connected load will be 120 volts, these arrangements will supply 60 amps @ 120V on a 30-amp connector and 100 amps @ 120V on a 50-amp connector”

    • Jim Herrick says:

      On a 30A multipole circuit breaker you can get 30A per pole.
      If it is fed by a 3-phase, 208V, 5-wire system L1, L2, L3, N, G you can get 90A at 120V;
      or a 240V, 4 wire system L1, L2, N, G you can get 60A at 120V.
      This applies to any size multi wire circuit (amperage per pole at 120V). Don’t forget to take into consideration any line-to-line loads (208V or 240V) in addition to the 120V loads. This will increase the amperage load on the feeder (main) circuit breaker.
      Using Watts (W) as a parameter, 30A at 240V = 7200W is the same as 60A at 120V = 7200W,
      since V x A = W.
      The 208V single phase results are a little different, due to the phase relationship timing among phases (line to line), but the math is still the same. 30A x 208V = 6240W, however 30A x 120V (line to neutral) is still 7200W. Three-phase 208V (line to line), is even more complicated and the “power factor” must be considered, but it has little significance at 120V (line to neutral) with regard to your question.

      Both the 208V and 240V systems must have a neutral that is common to each phase. This neutral will only carry the unbalanced load. The neutral current will not exceed the capacity of the combined load of the line (hot) conductors unless the load is “reactive”, such as a lot of dimmers or switching power supply loads. In this case an oversized neutral may be required. These are special circumstances; therefore, an oversized neutral is generally not required.

      Regarding the connectors you referenced in your question:
      A 30A, 120V, 3-wire connector (as an example) has 3 terminals: L, N, G. it is only rated for 30A max.
      A 30A, 250V, 3-wire connector (as an example) has 3 terminals: L1, L2, G is also rated for 30A max.
      A 30A, 250V, 4-wire connector (as an example) has 4 terminals: L1, L2, N, G is also rated for 30A max per pole.
      L1 to N = 30A at 120V + L2 to N = 30A at 120V. This will provide 60A at 120V and/or 30A up to 250V.
      Combination loads (120V and 250V) cannot exceed 30A on any line terminal. If you require 120V the circuits from this connector must be “split-out” to two 3-wire 120V connectors, L1, N, G and L2, N, G. In most cases a “breakered stringer box” can be used to split-out the circuits.
      Note: Connectors are rated at 250V, even though they are used on 208 or 240V systems, there are some exceptions.

      It is recommended that circuits are not to be loaded at more than 80% of their capacity.
      This provides a safety margin to prevent nuisance tripping of circuit breakers and overheating of bundled conductors, which would not be good during a show. The circuit breakers must not exceed the rating of the connectors.

      Jim Herrick

Leave a Reply

Your email address will not be published. Required fields are marked *