For general and accent lighting, architects love neon/cold cathode's color variety, efficiency and longevity, which other light sources can't achieve.
Conversely, architects hate neon/cold cathode, which must be customized and engineered for each application. Thus, installation problems occur when tubes aren't properly specified.
However, proper planning averts trouble – and architects' aversion. I'll discuss some successful architectural, cold-cathode installations that show why certain prejudices exist.
What I call "MMMs" (Most [frequently] Made Mistakes) begin when architects don't know that technical and installation code requirements regarding cold-cathode tubes aren't the same as those that govern ready-made lighting fixtures. Neon/cold cathode is one of the few light sources in which the lamp can be the luminaire (the complete lighting unit, which comprises the lamp, or lamps, and the parts designed to distribute the light, position and protect the lamps, and connect the lamps to the power supply) and, thus, a component of internal architecture.
Cold cathode can be even more spectacular on building facades, where it becomes a part of "art in architecture." In these situations, architects/planners often specify custom-designed fixtures that push neon far beyond its technical limits — and far beyond electrical-safety rules.
Industrial buildings repurposed as cultural centers and theaters are often retrofit with architectural, cold-cathode, accent lighting. In 2003, the Colosseum Theater, in Essen, Germany, was completely rebuilt in a 1906 brick building that formerly housed a heavy-machine shop. Warm-white and yellow cold cathode now outline the façade.Advertisement
All transformers were mounted indoors, almost directly behind the tube circuits; most were hidden in the building's steel-support structure. Where the silicone GTO penetrated the building, the GTO was installed in conduit (which the local electrical code didn't require).
Cold-cathode installations shouldn't cause any visible or structural damage to historic buildings. In this case, the tubes were directly mounted on the brick rims. Red, silicone GTO was fastened with small, acrylic, tube supports. The double-insulated electrodes (even the shrinkhose was rated for 284°F [140°C] continuous use) provided additional protection against accidental contact with live parts in the public area, in case the glass broke.
For similar U.S. installations, the National Electrical Code (NEC) requires more than in. between the glass tube and the nearest surface (other than the tube supports), independent of the voltage or current used in that particular circuit.
At the Colosseum, a bucket truck could readily access the tubes for service and cleaning. However, I've inspected many installations that required technical mountain climbers to access the tube or transformers — even in internal, atrium locations.
As in our example, vertically installed tubes can slip in the tube supports and thus touch the next tube. If double backs of adjacent tubes touch, the glass can break when the tubes expand.
To prevent this, generously space your tube sections. In our example, silicone-rubber hose pieces, slit lengthwise and slipped on the tubes, prevented the glass from sliding.Advertisement
Designers often desire invisible wiring and tube mounting. They essentially want a row of tubing that floats in space, which is impossible in the United States. The NEC states that high-voltage wiring must be installed inside metal tubing or conduit (which may be nonmetallic in a few cases). There's no alternative. Also, tubes must be securely fastened using listed tube supports.
I've inspected many external, accent-lighting installations in which the tubes' metal frames didn't meet the -in. (or equivalent European) regulation, and the tubes that touched the metal could be easily punctured by high-voltage arcing.
Pre-manufactured and pre-wired sections can prevent many site-installation problems. This also reduces the risk of onsite glass breakage. But, the technician must plan for easy service access that can be accomplished without special tools.
I remember one case in which the fixture couldn't be opened or disassembled without a special mounting bracket. A 38-ton, flatbed truck transported the fixture and bracket, and the neon shop that fabricated the fixture was in another country.
Forestall installers' curses
Like HID and low-voltage, halogen lamps, cold-cathode lamps require transformers or electronic power supplies. All neon shops know electronic, neon, power supplies must be mounted where the tube's located (the maximum GTO length is 2 to 3 ft.). Electronic power supplies aren't normally recommended for outdoor service, because humidity can influence high-frequency electricity.Advertisement
Also, magnetic (core-and-coil) transformers must be installed near the tubes. In high-impedance neon circuits, low-current, high-voltage electricity can't be run through long wires without creating trouble. I've explained why GTO wires must be short (see ST , January 2003, page 18, and October 2004, page 22).
To meet this requirement, architects must allocate enough space to provide ventilation and access to the transformers. One installation for which I consulted provided good ventilation – on the roof, in the desert sun of Dubai, United Arab Emirates — but the temperature far exceeded normal ratings.
The architects didn't permit the GTO to penetrate the wall or roof, so we mounted the transformers outdoors on the roof of the air-conditioned hall (an indoor skiing center). To accommodate the project, a German transformer manufacturer developed a transformer to withstand dust and tropical humidity without additional enclosures.
Although internal, cove-lighting installations seem to be far simpler, they also present architectural pitfalls. Electronic power supplies (and core-and-coil transformers) must be located at the tube, and they must also remain cool, because electronic devices and heat don't match. Simply dropping the tube, GTO and power supply in a cove will produce uneven shadows on the wall and ceiling. The cove's height and width must be carefully planned so the cove's front edge will block a direct view of the tubes from any location. Ray tracing (a rendering method that plots a view of every pixel in a scene through a virtual camera's lens) helps estimate angles and space.
In many installations I've seen, cove geometry didn't permit proper installation. In these cases, the coves were accessible only from the small space between the cove and drop ceiling, and the space could barely accommodate a hand, not to mention a drill or a screw gun.
The cove material often determines the tube supports. For example, on 1/3-in. sheetrock with the back side visible, I'd mount standard tube supports on a small piece of polycarbonate (maybe 3 x 3 in.), and glue that piece onto the sheetrock. Even -in.-long sheetrock screws will create a visible bulge on the other side.
Sideways forces may push the tube supports when tubes bend or stretch when heated. Yes, glass is flexible, but only to a certain point! Also, the tubes must be fastened to the supports, and the wiring must be properly laid – in the first installation and in subsequent service calls.
After the architect/planner has specified the cove (or profile, for external, accent lighting) dimensions, custom-shaped, glass-tubing sections must be carefully measured to avoid breakage and installation problems (see ST, April 2006, page 32). In the planning phase, architects unfamiliar with cold cathode's special requirements might consult a specialist (if someone isn't on staff). Too frequently, the neon shop gets involved when it's too late to make necessary changes.
Here's my main request of architects (sometimes nicknamed "construction artists"): Think of service! Lighting installations need periodic service. Don't make me repeat, in print, the curses service technicians have uttered.
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