Category: Lamps

Basking in a New Glow

The New York times has an “I Heart LEDs” article in today’s paper that leaves out some important information about evaluating them.  Here are some additional thoughts.

The government hasn’t done a very good job of publicizing or explaining that the Energy Independence and Security Act of 2007 (EISA) set minimum efficiency requirements for general use light bulbs (the act excluded decorative and colored products).  The incandescent lamp that’s been around for over 100 years doesn’t meet the energy efficiency standard.  Rather than re-engineer incandescent lamps, the lamp manufacturers have focused on expanding and emphasizing compact fluorescent (CFL) and light emitting diode (LED) technologies.  Again, you can still purchase 40 – 100 watt decorative incandescent lamps but not A-lamps, the most common shape in use.

The easiest substitution, one that requires no thinking about rewiring, dimming, etc., is the halogen lamp.  Halogen lamps are an improvement on standard incandescent lamps, and many of them meet the EISA energy efficiency requirements.

If you’re looking for higher energy efficiency, and are willing to pay a higher price up front to get it, CFL and LED lamps are available in a wide range of wattages and shapes.  However, they  need to be approached with caution.  Both technologies can be difficult to dim, especially with older dimmers that were designed with incandescent lamps in mind, so your existing dimmers may need to be replaced.  They can also produce unsatisfactory tints of white light.  LEDs are especially notorious for not matching the information provided on the packaging, as demonstrated through the Department of Energy’s CALiPER program.

Here’s what to look for.  Every light bulb package should have a Lighting Facts Label that looks like this.

Lighting Facts Label
Lighting Facts Label

The orange/yellow/white/blue color bar is where you’ll find information about the warmth or coolness of the light, both with an arrow on the color bar and with a number.  The number is called the Color Temperature (actually the correlated color temperature) and measures the warmth or coolness in Kelvin.  The important thing to know is that a lower number (2700 to 3000 K) is roughly equal to an incandescent light bulb.  As the number gets higher the light gets cooler.

Warmth/coolness isn’t the only measurement of the quality of light.  Another consideration is how well the light source allows us to see the colors of objects.  This is called Color Rendering (Color Accuracy on the Lighting Facts Label) and is indicated by a Color Rendering Index number.  Higher numbers (with a maximum of 100) indicate better color rendering, so a light with a Color Accuracy of 95 should be visibly better than one of 80.

The Color Rendering Index is not very specific, however, and is known to misrepresent LEDs.  Therefore you are the best, final test of whether or not a given light bulb is appropriate.  I recommend purchasing only one or two and trying them out for a few days before committing to changing over your entire house.

My other recommendation is to stick with the major manufacturers (GE, Philips, Sylvania) for most lamps that you test.  These companies have a track record of product consistency and quality that many of the newer manufacturers don’t.  I can almost guarantee that with an off-brand 5-pack of lamps for $10 you’ll get what you pay for and hate the results.  It’s not the technology that you’ll hate, but the manufacturer’s poor execution of the technology.

I hope this helps.

A Challenge for LED Luminaires

Today I was at an LED “shootout” at the New York City office of Barbizon (special thanks to John Gebbe and Scott Hali).  We were looking at products that might be used in a specific application – that of lighting an auditorium or theatre.  The shootout was between 26 fixtures from 17 manufacturers, all installed at a height of 10′.

Architecturally, the designer is essentially lighting three conjoined rooms:  the orchestra, where the ceiling can be 35′ high or more; the balcony, where the ceiling can range from 12′ to 25′ because of the steep slope of the seating; under the balcony, where the ceiling may range from 12′ to 18′, again because of the slope of the seating.

The first part of the challenge is to find a set of fixtures that can provide even illumination in these three spaces, each one of which has a sloped floor and therefore a  varying throw distance.  The second part of the challenge is for all of the fixtures to dim simultaneously.  Unfortunately, I don’t think we saw success.  Here’s what we saw.

First, only one manufacturer had a product line for all three possible mounting conditions – pendant, surface, and recessed.  That manufacturer, though, didn’t have three beam spread and/or brightness options to meet the range of typical installation heights.

Second, LED manufacturing is maturing, but it’s not mature.  That means we still don’t have strong, industry-wide standards for things like color.  In many cases it was difficult to use fixtures from two or more manufacturers because the color of the light produced (visually evaluated, and measured in color temperature, peak wavelength and spectral content) clearly didn’t match.

Finally, getting fixtures from multiple manufacturers to dim simultaneously proved very difficult.  Each set of installed fixtures would need its own (perhaps custom) dimming curve just to get a close match, and identical performance seemed impossible.   The problem here is three-fold.  First, multiple control protocols would be required.  The fixtures demonstrated used line voltage dimming, three-wire dimming, 0-10v DC, and DMX protocols.  That’s not a deal breaker, but it is an unfortunate complication.  Second, some of the LED drivers produced unacceptable dips, flickering, or pulsing of the light as they dimmed.  Third, some of the LED drivers couldn’t make a smooth transition from darkness or light, or light to darkness.  We saw fixtures pop on and drop out, dim up nicely but not dim out well, and dim out well but pop on.  Eventually this might be as easy as working with incandescent lamps, but not yet.

The easy lesson was that, for now, the safest choice for smooth dimming from darkness to full light is still incandescent.  The color of the light from fixtures in all of the installation conditions will match, the dimming curves will be the same, and they’re easy to dim.

The complicated lesson was that it is absolutely essential to mock up the proposed lighting system, using the LEDs, drivers, control protocols, and dimming equipment that will be installed.  It’s the only way to be certain that the start and end of a show, when the house lights dim down and then back up, isn’t a light show of its own.