TV production spaces, part II
Dec 1, 2008 12:00 PM, By Antonio Argibay, AIA
When designing lighting, power and electrical systems, consider these issues.
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.
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