Get the LED in? Shining light on LED fixtures in theatre auditoriums
The question of how much to invest in new lighting systems in the auditorium puzzles building owners and cinema operators alike. Based on our work with clients that are interested in controlling initial investments and long-term operational costs, we have developed this overview of items to consider when deciding whether to install LED lighting systems.
The first consideration should be cost. However, simply comparing the cost of an LED fixture to an incandescent does not tell the entire story. We have studied overall auditorium lighting requirements. With recent improvements in total lighting output from a single LED fixture, we can apply an LED design to total operational lighting needs and then compare the cost on a per-auditorium basis. Upon initial analysis, LED costs appear impractical. But our lighting team went to the next level to further study the comparable costs and options for creative lighting installations.
Typically, two lighting systems are used in the auditorium, including recessed incandescent fixtures controlled at the booth dimmer and 2’ x 4’ fluorescent cleanup fixtures switched at the auditorium entry. The independent cleanup lights are necessary because of the limited ability of the incandescent fixtures to provide viable light to clean the auditoriums between shows. Although necessary, we can lower the overall cost of this maintenance lighting by reducing the number of fixtures installed.
When considering what kind of LED fixtures to use, we recommend reviewing both performance and dimming capabilities when making a selection. We have designed lighting systems that allow adjustable dimmers to compensate for full-light cleanup mode and low-light pre- and post-show mode. Some dimmer manufacturers provide a bypass option or a separate bypass relay that can be added to the lighting panel. This bypass is particularly important to allow a morning crew to operate using cleanup lighting.
The ultimate goal for the LED design of any auditorium is to reduce the overall fixture count while maximizing the impact of the system. While reducing the fixture count helps to minimize costs, the greatest benefit is in reducing the contractor installation cost.
The cost of LED fixtures is continuing to drop as more manufacturers make the transition to the newer fixtures. A traditional 250-seat auditorium would have twelve incandescent house light fixtures and six fluorescent cleanup fixtures. These can be replaced by eight LED fixtures fulfilling both functions. With fewer fixtures to install and operate, the cost difference narrows to $1,500 per auditorium more for the LED solution. For a typical ten-screen theatre, this equates to a 38-cent-per-square-foot increase in construction costs.
As illustrated in the graph above, LED fixtures use less than half the energy of a traditional light. With normal electricity rates applied, this equates to a ten-year payback of the additional costs incurred. Since electric prices increase rather than decrease regularly, this solution makes sense over the term of the cinema’s life.
The other overwhelming reason to switch to LED lighting is lamp life. The life of an LED house-lighting system is three times longer than compact fluorescent lights and is 11 times longer than incandescent lights. Now for the tricky part of the comparison: How many of you have changed a light bulb in an auditorium ceiling which is located over existing seats and stadium seating? It is very cumbersome and in many instances requires erection of some kind of scaffolding to get to the light. The time and cost to replace the lamp means that your effective payback is really achieved the first time you have to change a house-light lamp.
This can also be analyzed from another perspective. The graph above depicts projected energy savings when comparing the two design strategies. As mentioned earlier, the LED design consumes less than 50% of the energy the standard design consumes. The consumption figures are based on an average cinema operation showing 30 films per week with a total of 29.5 total hours of non-dimmed lighting being used each week.
We are specifying fixtures that provide nearly zero to 100% control. The dimmer manufacturer we have found tested the fixture in their lab and found it to both dim well and start up in a more visually acceptable manner, meaning it comes up to full light softly. The driver is equipped with 120-volt, three-wire dimming control which includes a line voltage, dimmer control line and neutral. The manufacturer reports that by adding a ballast resistor across the output, their standard theatre dimmer performs “perfectly.”
Because LED and incandescent fixture dimming are different, standard dimming does not work with LED fixtures. As an incandescent fixture dims, there is lag time involved as the filament cools down. This lag allows for the soft dimming effect to which we have grown accustomed. LED chips create light instantly as they are energized. Dimming of LEDs occurs by controlling the power to the chip. The light is actually fluctuating at a pace that is unperceivable to the eye.
As dimming to 20% capacity meets most commercial dimming needs, development of a better dimmer has been slow. While the dimming driver we have found is not considered the most efficient by the lighting industry, it appears to be the best option available to exhibitors in the cinema industry. The problem has been that many customers are ordering LED fixtures and the demand is outpacing production. There has not been time left to conduct the research and development needed to perfect the dimmer system for auditoriums. Based on our experience with specifying, purchasing and installing LED fixtures, we expect newer technologies to be available within the coming months.
The cinema industry makes up only a small portion of the overall LED market, but its use is so well-suited to what LED can provide, we believe the technology will be available in the very near future to support LED installations in cinemas worldwide.
Stay tuned…we will keep you informed of the latest developments that come to light.
©TK Architects International 2013
Mike Cummings is a principal of TK Architects International. Brad Reynolds is in charge of mechanical, electrical and plumbing design. You can reach Mike at firstname.lastname@example.org or Brad at email@example.com.