In order to properly predict the performance of an LED lighting system and to accurately compare results to competing LED and conventional lighting systems, lighting engineers and designers must be particularly careful to use appropriate LED Maintenance Factors. Calculations to predict performance lighting installation are fundamental to the practice of lighting design and lighting engineering. These calculations allow lighting engineers and designers to predict lighting performance and whether the design meets and complies with the correct specification and performance recommendations. Talk by Darryl Bullock MSc BEng (Hons) BA CEng MILP MIET, National Project Manager of Light and Energy Design

1. Darryl Bullock,CEng,MSc,BEng(Hons),BA, MILP,MIET
National Project Manager

2. LED – Maintenance Factors
What Is The Correct Solution?
Lighting Design

3. Choosing the Correct Solution
• Energy
• Design Life
• Colour Temperature
• Optical Performance

4. Product reliability
As with all Luminaires Conventional or
LED, the overall product reliability is
determined by the integration of
packaging and assembly of components
into a final product, ensuring that each of
the component parts are adhered to with
respect to drive conditions and thermal
management.

5. Lumen Depreciation
Most LEDs experience a gradual reduction in light
output over the lifetime of operation
Lumen Maintenance
The reliability of the LED to maintain its light output
during operation
As such, any degradation or reduction in performance
can be either from a reduction in the light‐emitting
efficiency of the LED chip or a reduction in the light
transmission of the optical path within the LED
package, module or fixture.

6. Projected Energy Rise

7. Design Life
• The subject of maintenance factors for LED lanterns that
is a topic is a topic that is being raised on a frequent
basis.
• Lumen maintenance is taken from LM80‐08 report. All
reputable LED manufacturers produce TM21 data for
10,000 hours of operation of their LEDs at various drive
currents and junction temperatures which can be used to
extrapolate lumen maintenance at end of life.
• LM80‐08 recommends that the extrapolation period
should not exceed 6 times the test period, or 60,000
hours. However this is not helpful when trying to
predict 100,000 hours.

8. Common Denominators
• All lanterns are subject to the same MF relating to
cleaning frequency and environmental zone. So for
E1/E2 6m column 72 month cleaning frequency this will
be 0.92
• After this I think the chosen maintenance factor varies
from product to product depending on the information
available.
• Is this the case ??
• Less pollution

9. The life of LEDs
• The life of LEDs (Lx) is defined as the length of time
during which the LEDs will
• provide more than a claimed percentage (x) of the
initial light output.
• A manufacturer will declare values for life and lumen
maintenance, usually at a specified ambient
temperature.
• The factor Lx takes into account the general decline of
light output over life.
• In addition to this there is likely to be a failure of LEDs,
comprising both catastrophic (total)
• failure and a steep decline in light output to a value
• considered to be below acceptable operation.

10. Current Vs Light

11. Lifetime @ 700mA

12. Lifetime @ 350mA

13. Controlling Temperature

14. The failure rate over the rated life is defined
as the failure fraction (Fy)
• The failure rate over the rated life is defined as
the failure fraction (Fy) where y is the
percentage of LEDs that will have failed at the
end of rated life. For example, F10 (100000 h)
indicates that 10% of the LEDs will no longer
be considered operational at 100 000 h.
• For lighting design the failure fraction Fy needs
to be taken into account. Using the example, if
10% of the LEDs have failed then 90% will be
operational; this is equivalent to a survival factor
of 0.9.

15. L70 @ 35oC
Also known as L70B50
which is the point when
50% of the LED’s lose
30% of their Lumen
Output

16. What Drive Current
• For lighting design, the overall maintenance factor for
LED luminaires takes into account the following factors:
•
• • The lumen maintenance of the LEDs at the end of their
rated life – this is equivalent to lamp lumen maintenance
factor (LLMF);
•
• • The failure fraction of the LEDs at the end of their rated
life – this is equivalent to lamp survival factor (LSF);
•
• • The reduction in light output owing to the
accumulation of dirt on the light‐emitting parts of the
luminaire (luminaire maintenance factor, LMF) – typical
values are shown in Table B.1.

17. Environmental Zone

18. Maintenance factors for LED luminaires
Derived from using the above formula and the BS5489‐1:2013
BS13201‐3
(informative)
Maintenance factors for LED luminaires
Proposed Lantern –Mounting Height 8m
Maintenance Factor: Lantern L95/F5 = 50,000hrs – Cleaning
Cycle – 0.92
So the total MF for our luminaire = LMF x LLMF x LSF
MF= 0.95*0.95*0.92= 0.83
Intensity G4
Environment Zone ‐ E3
Proposed Lantern Mounting Height 5m
Maintenance Factor: Lantern L95/F5 = 50,000hrs – Cleaning
Cycle – MF= 0.95*0.95*084 = 0.76
Intensity G4
Environment Zone ‐ E3

19. Maintenance factors for CLO LED luminaires
(informative)
Often our customers are asking for Constant Light Output which
means the lumen depreciation is compensated for by increasing the
drive current over the life of the product.
In this case the MF used should be = LMF x LSF
Maintenance factors for LED luminaires
Proposed Lantern –Mounting Height 8m
Maintenance Factor: Lantern L95/F5 = 50,000hrs – Cleaning Cycle
So the total MF for our luminaire = LMF x LSF
MF= 0.95*0.92= 0.87
Intensity G4
Environment Zone ‐ E3
Proposed Lantern Mounting Height 5m
Maintenance Factor: Lantern L95/F5 = 50,000hrs – Cleaning Cycle –
MF= 0.95*084 = 0.79
Intensity G4
Environment Zone ‐ E3

20. NON CLO
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Start NON CLO

21. CLO
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CLO CLO Increase

22. Choosing the Correct Solution with an
Agreed Common Design Criteria That
Takes Away Any Confusion
Lumen Output (LED or Lantern)
Maintenance Factor Calculations
Allowing a Common Approach for Lighting
Engineers To Apply These To Their Designs

23. Thank You For Your Attention
Any
Questions
?