Results from Finelite PLS Lumen Maintenance Testing
and Use of IES LM-80-08 Data
This report is provided by Finelite Inc. and applies to lumen maintenance testing for PLS systems purchased after
January 1, 2008.
The purpose of this document is to describe the procedure used to determine the published L70 Lifetime rating for
the PLS luminaires and demonstrate that current industry standard procedures have been followed in the reporting
of PLS LED life.
LED lumen maintenance lifetime estimates for PLS luminaires are based on two primary sets of data:
(1) Independent tests performed on sample PLS luminaires, under standard conditions
These tests determine the PLS LED temperature performance in normal operation.
Finelite utilized services from CSA International to obtain this data. The CSA International
report contains In Situ Temperature Test Results for the PLS 6W and 9W Desk Lamps based
on the testing methods prescribed by the DOE Energy Star® program for Solid State Lighting
and IES LM-80-08. [Refer to Attachment A.]
(2) Lumen maintenance of the individual source LEDs under specific temperature and power conditions
This data comes from the manufacturer of the LEDs at a component level. Finelite uses Nichia LEDs
in PLS, and Nichia has provided lumen maintenance data for their specific model LED used in PLS
systems. Because Nichia’s lifetime experiments were started before IES LM-80-08 was published, it
was not possible to follow all specific testing procedures prescribed by IES LM-80-08. However,
Nichia’s experiments did follow industry standards relevant at the time their testing began, and
used LED temperatures that exceeded those required by IES LM-80-08. In addition, the Nichia data
includes 10,000 hours of data, substantially longer than the 6,000 hour minimum requirement in
IES LM-80-08. [Refer to Attachment B.]
When combined, these data sets provide a method for Finelite to estimate the lumen maintenance of PLS
luminaires. Data from the 6W and 9W Desk Lamps as presented serve as a conservative estimate of life for
the entire family of PLS luminaires. Measured data and L70 lifetime estimates are summarized below.
Summary of PLS Lifetime Test Results:
Temperature on outside of LED package
LED case temperature Tc (a)
6W @ 52 °C
9W @ 65 °C
Internal Temperature of the LED chip
LED junction temperature Tj (b)
6W @ 62 °C
9W @ 75 °C
Lumen maintenance @ 6,000 hrs (c)
99.3%
Lumen maintenance @ 10,000 hrs (c)
91.2%
Number of hours to 70% Lumen maintenance
L70 Lifetime estimate (d)
> 50,000 hrs
— Refer to next page for footnotes a, b, c, d.
Finelite, Inc. • 30500 Whipple Road • Union City, CA 94587-1530 • 510 / 441-1100 Fax: 510 / 441-1510 • www.finelite.com
a. LED case temperature Tc (also referred to as the solder point temperature Ts)
This is the location on the LED where the temperature measurements are taken since it is
not physically possible to measure the LED junction temperature (Tj) directly. Tc is used to make
indirect temperature measurements of Tj. Refer to Attachment A for CSA International independent
test measurements of Tc.
b. LED junction temperature Tj
The LED junction temperature determines the lumen maintenance performance of the LED. Lower
temperatures give improved lifetimes. Tj is calculated from the case temperature Tc and the power
dissipated in the individual LEDs. LEDs in the PLS systems covered by this report are driven at 1 watt
per LED. The thermal resistance provided by Nichia for the 083A LED package is 10 °C per watt,
and so Tj in this application will be approximately 10 °C higher than Tc. Note that the 10°C per
watt resistance is a maximum value, and thermal resistances for real world systems will vary slightly
between individual LEDs.
c.
Nichia-measured lumen maintenance data
At 6,000 hours of operation, the Nichia LEDs maintain over 99% of their initial light output (lumens).
At 10,000 hours of operation, the Nichia LEDs maintain over 91% of their initial light output (lumens).
This lumen maintenance data is based on conditions of operation in PLS luminaires.
d. Nichia engineering estimate of L70 Lifetime
The L70 Lifetime represents the number of hours where 70% or more of initial light output (lumens) is
maintained. Finelite has submitted the PLS thermal testing results to Nichia for review. Their engineers
provided the L70 +50K hour lifetime estimate based on internal testing performed by Nichia and informed
by their substantial experience with LED chip, package, and phosphor technologies. As of the writing of
this report, there is currently no industry standard for estimating L70 LED lifetime. IES LM-80-08 provides
for standard testing procedures to measure actual lumen depreciation but provides NO method for
extrapolating the results. An IES working group (TM-22) is formulating mathematical algorithms that can
be used for these extrapolations, but until this work is published it remains up to the individual LED
manufacturer to provide these types of lifetime estimates. [Refer to Attachment B.]
Certified by:
Finelite, Inc. • 30500 Whipple Road • Union City, CA 94587-1530 • 510 / 441-1100 Fax: 510 / 441-1510 • www.finelite.com
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