Page 21 - IEC Insights Jan-Feb2020

ighting used to be simple. The Illuminating Engineering Society good reason. Just like discharge sources,
Install the light fixture, screw (IES) publishes American National LED output depreciates over time. The
in the light bulb, flick on the Standards (i.e. ANSI) for LED metric most commonly referenced
breaker and the switch and measurements. Established in 1906, when setting LED product life claims is
Lthere’s light. Enabled by North the IES is the recognized technical and luminous flux maintenance (aka lumen
America’s relatively cheap electricity, this educational authority on illumination. maintenance). And just as 70% of initial
simplicity includes a massive amount of For over 100 years our objective has flux is a typical threshold for fluorescent
wasted electricity and money. Standard been to communicate information on all group relamping, 70% is an accepted
incandescent bulbs emit less than 10% aspects of good lighting practice to our threshold for replacing LED products.
of input power as light, the other 90% members, to the lighting community, ANSI/IES LM-80-15, the IES Approved
as heat creating more air circulation and to consumers through a variety of Method for Measuring Luminous Flux and
and cooling needs, and electrical load. programs, publications, and services. Color Maintenance of LED Packages, Arrays
Halogen incandescent improves the IES members include engineers, and Modules is the standard for measuring
efficiency a bit. Discharge technologies architects, contractors, designers, luminous flux maintenance of LEDs.
(e.g. fluorescent, HID, high pressure educators, students, distributors, “LM-80” measures luminous flux of LEDs
sodium) are much more efficient and utility personnel, manufacturers, over time, as a function of temperature.
generate less heat, with the downside of and scientists, all contributing to the Importantly, what is tested is the LED
both bulbs and ballasts needing periodic mission of the Society: to improve packages, arrays or modules, the discrete
replacement, creating an e-waste stream. the lighted environment by bringing subcomponents within bulbs and fixtures.
together those with lighting knowledge The resulting LM-80 test reports include
Solid-state lighting has ushered in a new and by translating that knowledge luminous flux and color values over time
era of energy efficiency that Thomas into actions that benefit the public. for the LED devices operating at 55°C,
Edison himself surely would have 85°C, and often higher temperatures.
embraced. Well-designed LED bulbs and LED bulb or light fixture life is a function
fixtures (aka LED lamps and luminaires) of its weakest link. Either the source and/ Here’s where the problem begins, and
use less electricity than fluorescent, with or its ballast or driver will fail first, or where you can add real value for your
much longer life. Whereas incandescent second as a result of housing failures. clients. Before LEDs, lamp lifetime was
by definition provides light as a byproduct But unlike preceding light sources the established by burning a group of bulbs
of heat, LEDs generate much less heat LEDs within an LED lamps or luminaire until 50% of them had failed, and that
as a byproduct of producing light. It is are typically not serviceable. Just as a duration informed the product’s lifetime
this advantage in thermal management transistor radio contains transistors, an rating. If 100 bulbs were placed on test
that allows LEDs to last so much longer. LED bulb or fixture contains irreplaceable and the 50 failure occurred at 1,073
th
light emitting diodes soldered to a board; hours, the manufacturer rated the bulb for
True LED lamp and luminaire life however often the LED driver powering the LEDs is 1,000 hours, as captured in IES standards.
depends on a number of important also not replaceable. Many manufacturers With LEDs, testing to 50,000 hours (a
factors, thermal performance being one assume that property owners will be common life rating) would take nearly
of them, and exaggerated lifetime claims inclined to renovate a space around the six years, and 100,000 hours, more than
— the kind we’re seeing a lot of — often time its light fixtures reach end of life; a decade. This is obviously impractical.
result from misunderstandings about that remodel will replace the fixtures
the industry standards underpinning anyway. For that reason, they include no The solution from the IES Testing
such claims. Unfortunately, many others provisions for upkeep of the fixture as it Procedures Committee is to measure
are the result of willful efforts to misuse is envisioned to become trash after, say, LED luminous flux at regular intervals
the standards in a meaningless game of 50,000 hours of operation. Especially over 6,000+ hours per LM-80, and to
specsmanship usually taking the form of for hard-to-reach fixtures with integral use a standardized calculation to project
LED product lifetimes defined in hundreds LEDs, this lack of maintainability makes to a point in the future when flux levels
of thousands of hours. For example: a rigorous fixture specification process should reach 70% of initial light output.
300,000 hours for a streetlight would be all the more important. Replacing a The calculated time (in hours) until an
north of 34 years of continuous operation. transistor radio is easy. Hiring multiple LED reaches this threshold is called L₇₀,
Are we to believe this fixture will last 68 trades to replace a single trimless as defined in IES TM-21-11, Projecting
years at 12 hours on / 12 off? The LED recessed can that fell far short of its Long Term Lumen Maintenance of LED
lamp and luminaire market has run amok lifetime rating is an expensive nuisance. Light Sources. With this standard, a
with overrated lifetime claims. Armed 6,000-hour LM-80 report, and the
with a simple calculation and a willingness Though LED driver failures, broken temperature of the LEDs measured inside
to stubbornly defend common sense, fasteners and weathered optics are all a product, a manufacturer can calculate
you the informed electrical contractor reasons for replacing a fixture, it’s the the projected luminous flux maintenance
can help bring these games to an end. LEDs that are most scrutinized, and for for those LEDs in that application, e.g.

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