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Lamp life and efficacy: Your guide to industrial lighting, Part 2

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Asking questions is key to a successful lighting upgrade

Upgrading to new, energy efficient industrial lighting can be a wise investment, offering reduced electricity bills, improved safety and productivity, and less maintenance.

However, it pays to learn a bit about lighting in order to ask good questions of your vendor, and ensure you’re getting the lighting system that best suits your needs.

To help industrial companies prepare for lighting retrofits, we've summarized tips offered by BC Hydro engineers Brian Friedman and Jason Zhang at the Power Smart Forum last fall. In Part 1, they covered how to assess your lighting needs, plus light quantity and quality; we continue with Part 2 below. You can also access their presentation slides online for more information.

1. Lamp life: new technologies bring new measures

How long your lamps will last has a direct impact on two types of costs: both the replacement cost for a new lamp, and maintenance. In many industrial facilities, high bay production rooms mean that changing light bulbs is a time-consuming task that may require special equipment and/or a stoppage in production. Therefore, lighting manufacturers typically give an expected life span for their lamps.

Traditionally, this was assessed by testing a batch of lamps together. The length of time it took for 50% of them to burn out was the accepted lamp life for that particular model. However, Friedman says the advent of LEDs has changed the equation.

"LEDs just will not burn out," says Friedman. "They'll glow and glow even though they have no useful light output after a certain point." For this reason, assessing a lamp's "lumen depreciation" has become more relevant: how the amount of light produced by a lamp declines over time.

Notations such as "L70=100,000 hours" have become mainstream. This means that the lamp will last 100,000 hours before its light output has depreciated to 70% of its original level. However, a rival lamp may offer "L90=80,000 hours," making it hard to compare technologies.

Zhang recommends being clear about the light level required for a task, and discussing needs thoroughly with a vendor. It's also important to assess the expected performance of a given technology in your specific application. For example, heat can cause a more rapid decline in some LED lamps, so if your facility is typically hot, this is a question to ask.

The upside is that LEDs fade slowly rather than failing outright, so with planned replacement schedules it's possible to avoid sudden losses of lighting.

2. Lighting efficacy vs. efficiency

Another set of concepts that can be confusing (even those in the industry sometimes stumble over the terms) is that of "efficacy" vs. "efficiency."

Efficacy has to do with the light source itself: how well it converts electricity to useable light, expressed as lumens (light output) per Watt (electricity input), or lm/W. As technology evolves, researchers are developing light sources with ever-higher levels of efficacy.

However, the lighting we purchase and install consists of numerous components, including the light source, ballasts or drivers that provide electricity to the source, reflectors and lenses that help direct the light, and housing that holds it all together. Efficiency is a measure of how well the entire luminaire (fixture) performs, expressed as a percentage ratio of total lamp lumens vs. useable output lumens.

It's possible for a luminaire to contain a light source (i.e. an LED array) with high efficacy, but to perform inefficiently due to its design. Once again, this is a reason to ask questions of your vendor.

Zhang and Friedman recommend working closely with your vendor and contractors to determine the lighting system – including lamps, controls, and design (placement) – that will be most effective for your facility and production needs. "Try some samples," says Zhang. "See whether your staff like it. Even for us as lighting experts, there are things you can't determine from the marketing materials. You have to see the samples, and try them."

"Far too often we've visited a site where a company gave the vendor or contractor total control over a lighting project, only to find out at the end of it that it doesn't adequately suit their needs," says Friedman. "It's important to stay involved, so that after you've made the investment, you have the right lighting system you want."

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Read Part 1 for details about light quality (colour temperature, colour rendering and spectral distribution) and quantity (lumens, lux and luminance).