TV production spaces, part II

When designing lighting, power and electrical systems, consider these issues.
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At the heart of all TV production spaces are the electrical systems. Whether selecting systems for illumination, cameras or microphones, it is essential to understand the options available in order to select the most effective systems for your project. This article will address three primary components: lighting, low-voltage wiring and utility power.

Production lighting rigging systems

The ceiling of a TV studio is a confusing mixture of wires and lights, with no apparent order. With experience, you begin to understand the benefits, limits and applicability of the different methods of supporting the production lighting or rigging. There are four types of lighting systems: dead hung, counterweight, catwalk and motorized. (See Figure 1.)

Dead hung

Figure 1. The four different types of rigging systems  Click to enlarge

Dead hung systems are the most commonly used today and the least expensive to install. They consist of a 1 1/2in pipe grid, spaced at regular intervals between 4ft to 5ft. One set of pipes is supported from the structure above it by 1/2in rods, at intervals matching the grid. The other set of parallel pipes is installed on the underside and perpendicular to the supporting pipes creating the grid. The lighting strips, or battens, for the dimming circuits are clamped to the piping or to the rod supports. The clear benefits of dead hung systems include:

  • They are inexpensive.
  • They require little skill to plan and install.
  • They are flexible and don't require maintenance.

However, they have limitations:

  • Their flexibility is limited to low grids (14ft range) and to productions that require few lighting changes.
  • For grids higher than 14ft, ladders are impractical. Genie lifts or other lift devices are generally required. These are difficult to maneuver around a set and may require bridging, moving sets or compromising a lighting plan to provide access.
  • These systems can be extremely time-consuming, thus inefficient for a production in which the need to access lighting instruments is frequent.

Counterweight

Counterweight systems involve the installation of a parallel piping system, with pipes spaced approximately 4ft from each other and broken into segments of 15ft to 20ft along its distance, which is the width of the studio. One wall, for the whole studio length, is devoted to the counterweights; ropes and the catwalk above are used for loading the weights. These systems have been in use for many years and were derived from theatrical technology. The benefits include:

  • Lights can be lowered to the studio floor to load the lighting instruments.
  • Lighting can be lowered for adjustments with manageable access of a ladder or genie lift.
  • As a system for accessing the lighting support, it is relatively inexpensive.

However, there are limitations:

  • It requires maintenance and inspection, including periodic reroping.
  • Cross-piping (linking two parallel light supports with a short, independent pipe) is problematic.
  • With tall sets, it is not easy to lower the lighting support to easy reach.

Catwalks

Catwalk systems consist of parallel walkways, typically 18in across, with in-between openings that allow the lighting instruments to be lowered and controlled from above. (See Figure 2.) The lighting connector strip, above each row of catwalks, runs the whole catwalk length. Lighting instruments are mounted on telescopic poles, and the poles are clamped to steel supports along the railing or spanning the openings.

They are accessed by stairs, typically located outside the studio. Catwalks are used only in studios with high ceilings (35ft or more), as the bottom of the catwalks is usually installed at approximately 24ft, requiring another 10ft to 12ft above to maneuver the poles.

Catwalk benefits include:

  • The system provides complete flexibility for locating lighting.
  • Instruments are always accessible from above, and technicians never have to move scenic elements to reach lighting adjustments.
  • It is extremely quick. As technicians are working above, actors, talent and directors can block scenes and do other studio preproduction tasks.
  • It does not require maintenance.
  • For scenic-intensive productions, such as soap operas, or for studios that need to move scenic elements often — and quickly — this system allows technicians to move on two levels, providing the quickest setup turnaround. However, all of this comes at a cost:
  • It is a heavy system, typically adding 35lbs per square foot to the structure.
  • Catwalk systems require custom design by a professional.
  • The system is relatively expensive and takes quite a bit of time to fabricate and install.

Motorized and hybrid

Motorized rigging systems have evolved in recent years. Their reliability, cost and versatility make them part of many production rigging solutions. Motorized solutions range from individual hoist luminaries to self-climbers with integrated lighting battens to fully motorized studio rigging systems. Typically, each motorized lighting batten is attached to a parallel track that supports each end of the batten. The batten then moves horizontally, like a train on tracks, back and forth, as required, for a range of 5ft in either direction. The latest motorized units don't require to move parallel to each other — or even perpendicular to the track. Other motorized systems include the raising and lowering of rectangular truss structures with lighting.

Benefits of motorized systems are:

  • Many motorized solutions are part of upgrading existing dead hung systems, thus creating a hybrid.
  • They require little maintenance.
  • They necessitate less gross ceiling height to get a net production ceiling height.
  • They can be incrementally installed and expanded as part of a planned upgrade.
  • Fully motorized systems can include horizontal tracking so that lighting can be put exactly where it's wanted.
  • They are reliable and easily integrated with DMX controls that may already be in use.

However, motorized systems require the following considerations:

  • They need substantial vendor support. Be sure you can get both parts and maintenance.
  • They still are relatively expensive.
  • Motorized systems require a structural subframe or another similar element attached to the systems' structural rails.
  • Mechanical things require some maintenance and break down. Carefully select the manufacturer and the supply chain, along with ironclad guarantees.

The lighting system

All lighting connected to the rigging is powered by lighting battens, also called connector strips. They are labeled with individual dimmer circuits and distributed in a balanced manner throughout the studio. The designer of this electrical system has to work hand-in-hand with the designer of the production lighting system to create a flexible, balanced distribution system.

Lighting power distribution and control

In the United States, when power is delivered to the entrance point by the utility, the first step is to provide an isolation transformer (ΔY), which takes the 480V distribution voltage in delta (Δ) and transforms it to 120V-208V in Y. This helps to prevent harmonics from feeding back to the utility. From the isolation transformer, power goes to distribution boards, which feed power via a main electrical wireway to smaller, individual branches for each lighting batten/connector strip in the studio. The individual branch electrical wireways end in a terminal box where the lighting battens are connected.

The lighting batten, usually a premanufactured and prewired element with the lighting connectors specified, is ready for connection in the field to an existing terminal box. Each outlet corresponds to a numbered dimmer circuit. Typically, they are 20A outlets with three (depending on the length) 60A outlets for the bigger lights (6000W). Numbering is traditionally done with the lower numbers for the 20A circuits, such as 42 through 90, and using larger numbers, such as 601, 602 and 603, reserved for the 60A outlets.

The number of ceiling dimming circuits installed is an important consideration when planning the studio. One per 15sq ft is reasonable; however, there can be greater or lesser densities based on preference or need. Floor-level circuits should be provided at one-third points along walls. Install four 20A lighting connections and one 60A connector. On the short walls, center another cluster of four 20A outlets. In studios where variety and musical shows are common and follow spots are required, provide a 100A outlet for each studio. Minimum #10 AWG conductors are needed to feed the 20A lighting dimming circuits. The lighting batten ground wire should run back to the panels/common ground location; use a minimum #8 AWG wire.

Here are two final thoughts regarding the power for the lighting systems. First, all dimmer circuits require a dedicated neutral, and failure to provide it will result in the electronic hum typically associated with shared neutrals. Second, all electrical loads must be balanced. This requires location planning of dimming circuits so that loads are evenly distributed over the electrical phases throughout the production area. Always consult a production lighting designer.

Low-voltage distribution

All TV studios require the installation of low-voltage broadcast cabling paths. Every studio needs boxes with video and audio terminals to which cameras, microphones and other broadcast equipment are connected. These boxes must be fed with a variety of cables, which, in turn, find their way to a production control area. Of these, only microphone cables must be kept in an electrical conduit all the way from the box to its final termination. The conduit provides additional shielding, and prevents intrusive electrical interference and noise.

The locations of these boxes are optional and are chosen for convenience based on the studio size and the productions that are planned. In smaller studios, install them so they can cover a radius of 30ft. In larger studios, such as sound stages designed for flexibility and a variety of productions, the radius can be increased to 50ft. In specialized production spaces, the placement should be closely coordinated for easy technicians' access and to accommodate the placement of scenic elements.

Be sure all the boxes are properly incorporated into your overall facility's wire management strategy. All drawings and plans should indicate the location of the boxes, cable trays and conduits.

Studio lighting is controlled through low-voltage DMX controls that require empty conduits and boxes for the installation of the control wiring. DMX boxes are typically provided at the ends of the studios and adjacent to the personnel doors. Additional locations are likely and will depend on specific applications.

Other considerations

One overlooked part of a studio lighting system is the need for work lights or house lights. These are used during studio maintenance, sets installation and for general lighting. Use fluorescent-based luminaries with as few lumens as possible per size of the light. The smaller the light, the less chance it will be on top of a production light. High-intensity discharge (HID) lighting can be used, but due to the long warm-up period, you would be well-advised to understand its implications. Incandescent 500W and more lights are also used in studios of various heights, but they are more expensive to operate and need more frequent bulb replacement than ballasted fixtures.

Additionally, building codes require egress signage and lighting. The first has to be closely coordinated with the set design and studio production. Designing the emergency lighting usually involves selecting a group of house lights and placing them on an emergency circuit that is backed up by a generator or battery system.

As a final note, production spaces must be provided with standard utility 120V power to operate tools and to power set elements, such as TV monitors, set lights, etc. This, too, should be planned for flexibility and coordinated with the other studio requirements. Also, it is customary to provide a company switch of 200A (or as-required amperage) 120V-208V for main power distribution. This service has circuit breakers and a series of cam and lug connectors on the bottom, which, in the better models, are behind a door that prevents tampering or accidental disconnects. They should be equipped with an external safety disconnect switch for safety.

In closing

This article provided an introduction to the most salient issues regarding electrical design of a production space. The tasks of designing a system fall largely upon an electrical engineer — someone who may understand his profession well but who often lacks any experience in the issues discussed in this article. It is important that the production manager, lighting designer, engineering department and architect all work hand-in-hand to satisfy the specific requirements of your project.

Antonio Argibay, AIA, is a principal of Meridian Design.