PLS 2019: Maintenance factors update – review of the new ILP Guidance Note and the ISO/CIE recent report

Nigel Parry
nigel.parry@orangetek.co.uk
13
th
June 2019

Maintenance Factors
13
th
June 2019
ISO/CIE TS 22012:2018 (ISO TC 274) Light and Lighting –
Maintenance Factor Determination – Way of Working.
ILP LED Maintenance Factor Guidance Note.

The International Commission on IlluminationInternational Commission on IlluminationInternational Commission on IlluminationInternational Commission on Illumination - also known as the CIECIECIECIE from its French
title, the Commission Internationale de lCommission Internationale de lCommission Internationale de lCommission Internationale de l´´´´EclairageEclairageEclairageEclairage - is devoted to worldwide
cooperation and the exchange of information on all matters relating to the science
and art of light and lighting, colour and vision, photobiology and image technology.
With strong technical, scientific and cultural foundations, the CIE is an independent,
non-profit organization that serves member countries on a voluntary basis. Since its
inception in 1913191319131913, the CIE has become a professional organization and has been
accepted as representing the best authority on the subject and as such is
recognized by ISO as an international standardization body.

Division 1: Vision and Colour
To study visual responses to light and to establish standards of response functions, models and procedures
of specification relevant to photometry, colorimetry, colour rendering, visual performance and visual
assessment of light and lighting.
Division 2: Physical Measurement of Light and Radiation
To study standard procedures for the evaluation of ultraviolet, visible and infrared radiation, global
radiation, and optical properties of materials and luminaires, as well as the optical properties and
performance of physical detectors and other devices required for their evaluation.
Division 3: Interior Environment and Lighting Design
To study and evaluate visual factors which influence the satisfaction of the occupants of a building with
their environment, and their interaction with thermal and acoustical aspects, and to provide guidance on
relevant design criteria for both natural and man-made lighting; as well as to study design techniques,
including relevant calculations, for the interior lighting of buildings; incorporating these findings and those
of other CIE Divisions into lighting guides for interiors in general, for particular types of interiors and for
specific problems in interior lighting practice.
Division 4: Transportation and Exterior Applications
To study and prepare guides for the design of exterior lighting and light signalling.
Division 6: Photobiology and Photochemistry
To study and evaluate the effects of optical radiation on biological and photochemical systems (exclusive of
vision).
Division 8: Image Technology
To study procedures and prepare guides and standards for the optical, visual and metrological aspects of
the communication, processing and reproduction of images, using all types of analogue and digital imaging
devices, storage media and imaging media.

DIVISION 4: TRANSPORTATION AND EXTERIOR APPLICATIONSDIVISION 4: TRANSPORTATION AND EXTERIOR APPLICATIONSDIVISION 4: TRANSPORTATION AND EXTERIOR APPLICATIONSDIVISION 4: TRANSPORTATION AND EXTERIOR APPLICATIONS
CIE Division 4, one of the six Technical Divisions of the International Commission on Illumination (CIE).
Division
Director
Dionyz
Gasparovsky
Division
Secretary
Maurice
Donners
Division
Editor
Nigel
Parry
Associate
Director
Steve
Fotios
Associate
Director
Sermin
Onaygil
Associate
Director
Raoul
Lorphevre
4-33 Discomfort Glare in Road Lighting
4-45 Performance Assessment Method for Vehicle Headlamps
4-47 Application of LED's in Transport Lighting and Signalling
4-50 Road Surface Characterization for Lighting Applications
4-51 Optimization of Road Lighting
4-52 Lighting for Pedestrians: New Empirical Data
4-53 Tunnel Lighting Evolution
4-54 Road Lighting for Ageing Drivers
4-55 Guide for the Lighting of Sport Events for Colour Television and Film Systems
4-56 Masterplanning Urban Lighting
4-57 Guide for Sports Lighting
4-58 Obtrusive Light from Colourful and Dynamic Lighting and its Limitation
4-59 Guide for Lighting Urban Elements
JTC 11 (CIE-ISO) Light and Lighting – Maintenance factor –
Way of working
JTC 13 (D4/D3) Depreciation and Maintenance of Lighting Systems

Maintenance Factors
13 June 2019
High Intensity Discharge (HID) Lamps

Luminaire Maintenance Factors HID Lamps
For lighting design, the overall maintenance factor
for all Luminaires is derived from:
• the lamp lumen maintenance factor (LLMF),
• the lamp survival factor (LSF) and
• the luminaire maintenance factor (LMF)

Lumen Depreciation
~20-50%
Lamp Mortality
~50%
Typical Rated Life
8,000-24,000 hours

Lamp CCt Watts Lm/w Ra Lamp Life
70wSon 84 100 <25 20,000
35w SOX 45 140 0 12,000
70w MBI 84 76 60 8,000
36w CFL 38 80 80 12,000
100w T 100 12 99 1,000

Maintenance Factors
13 June 2019
Light Emitting Diodes (LED) light sources

Initial/Early guidance was risk adverse and proposed for LED luminaires we need to use different
parameters to establish a meaningful Maintenance Factor for Road Lighting designs.
Thus LLMF and LSF shall be replaced with Lx, By, Cy and Fy where:
Luminaire Maintenance Factors
• Lx = lumen depreciation for a set period or ‘rated/useful life’ (50,000,84,000,
100,000 hours)
• By = the number of burning hours at which a given percentile of LED luminaires
cannot meet the lumen maintenance factor x.
• Cy = The abrupt light output degradation of a LED luminaire Cy (equivalent to a lamp
failure
• Fy = Failure Fraction - 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.

• To allow comparison between manufacturers the same useful life should
be provided for each luminaire. This useful life could be at 84,000hours
• A manufacturer will declare values for Useful Life and the maintenance
factor x at a specified ambient temperature.
• For example, L80B10 (50 000 h) at 25 °C indicates that after an operating
time of 50 000 h, 80% of the initial luminous flux will be emitted for a
luminaire operating in an ambient of 25 °C. Using this example, the LED
lumen maintenance factor is 0.8 at 50 000 h. The gradual loss of light is a
specific characteristic of a luminaire and cannot be assumed from a
knowledge of the performance of its components.
Design Example:

Design Example:

Maintenance Factors
13 June 2019
New Guidance
CIE

TS22012:2018
• Background information with respect to the principles of the
maintenance factor and the relevant parameters for indoor and
outdoor applications.
• A detailed way of working on how to apply the maintenance factor
determination method (as described in CIE 154:2003 and CIE
097:2005) for outdoor and indoor lighting designs using the
technologies available in the market.
• Explanation and examples on how to apply the maintenance factor
and how to ensure proper operation over time corresponding to the
determined values.

Maintenance factor determinationMaintenance factor determinationMaintenance factor determinationMaintenance factor determination
Basic description of the methodBasic description of the methodBasic description of the methodBasic description of the method
The maintenance factor fm is determined using the formula:
fm =fLF∙fS∙fLM∙fSM
where
fLF is the luminous flux factor
fS is the survival factor
fLM is the luminaire maintenance factor
fSM is the surface maintenance factor

To Note:
In some cases the depreciation values will be presented as the median useful life,
Lx, or the useful life ‘Lx,By’ value.
• In both cases, only the x value of the Lx value is relevant for the luminous
flux factor determination, the By element of ‘Lx,By’ is not taken into account in
the fLF and consequently the fm determination (e.g. the luminous flux factor
݂୐୊ ൌ 0,80 after 50 000 h for both tL80,B50 =50 000 h and tL80,B10 = 50 000 h
specifications).
In some cases the depreciation values will be presented as ‘LxFy’ values.
• The ‘LxFy’ is a (no longer in use) indication of lifetime not just taking into
account depreciation, but takes into account multiple maintenance factor
parameters (namely luminous flux depreciation and survival factor). As such,
this value is not appropriate for the determination of the maintenance factor
as it does not allow for separation of the luminous flux factor, fLF, and the
survival factor, fS. .

Maintenance Factors
13 June 2019
New Guidance
ILP

Maintenance factors are applied to
luminaire photometric data to ensure
that at the end of scheme’s design life,
in the worst-case scenario, the
specified lighting level is still
maintained.
The maintenance factor applied for a
luminaire should reflect how the light
output reduces over time due to a
variety of factors including lumen
depreciation of the light source and the
build-up of dirt on a luminaire. BS
5489-1: 2013 Annex C has long
provided the recommended method
for calculating maintenance factors in
the UK.
BS PD ISO/CIE TS 22012:2018 Light and
lighting. Maintenance factor determination.
Way of working is the latest best practice
guidance on the determination of
maintenance factors and provides much
needed clarity on the methods of calculation
and the reader is recommended to read that
document in detail for further guidance.
• TS 22012 recognises the weaknesses of the
guidance in BS EN 62717/62722 relating to
the LxBy parameter and provides a defines a
new slightly revised parameter for
determining maintenance factors, Lx,By
making it clear that the median useful life,
Lx (LxB50) should be used for determining
maintenance factors.
BS5489BS5489BS5489BS5489----1: 20131: 20131: 20131: 2013

Annex C sets out Informative guidance on calculating the
Overall Maintenance Factor (OMF) as:
OMF = LLMF x LSF x LMF where
LLMF is Lamp [or LED] Lumen Maintenance Factor
• representing the proportion of initial light output
remaining at the median useful life;
LSF is Lamp [or LED] Survival Factor
• representing the proportion of LEDs in a luminaire
that are expected to remain working at the median
useful life;
LMF is Luminaire Maintenance Factor
• representing the dirt build-up and other deterioration
of the optic surfaces/materials as BS 5489-1: 2013
Annex B, Table B1.
BS5489BS5489BS5489BS5489----1: 20131: 20131: 20131: 2013
IMPORTANT: For tenders and
lighting scheme comparisons,
the overall maintenance factor
for each luminaire make and
model should be determined
separately using manufacturers
published LLMF and LSF value.
The use of a “one size fits all”
maintenance factor can
underestimate the performance
of well-designed lanterns and
overstate the performance of
luminaires using low quality
components, skewing the
results

Maintenance factors have an impact
on the apparent efficiency of
luminaires in a lighting scheme and
particularly if assumptions are not
applied consistently across all
parameters.
If using CLO, to ensure performance is
as expected, the overall maintenance
factor should be matched with the
CLO factor to ensure that light levels
are maintained at or above the
required minimums and that power
consumption at any time during the
life of the product is sufficient to
achieve the light levels.
Finally, a single universal parameter for
Overall Efficiency is proposed here for
inclusion in Tender Specifications. This
parameter allows direct comparison of
the Overall Efficiency of different
manufacturers’ luminaires at the end of
scheme life including the effects of TM-
21 expected lumen depreciation, applied
maintenance factors and the impact of
Constant Light Output (CLO) on power
consumption. This parameter bridges
the gap between lighting standards, CLO
and power consumption over life,
improving the reliability of luminaire
performance comparisons.
MFMFMFMF –––– Constant Light Output (CLO)Constant Light Output (CLO)Constant Light Output (CLO)Constant Light Output (CLO)

Report includes useful
information on LED module
circuit architecture and testing
flow chart

Maintenance Factors
13 June 2019
LM80
TM21

Maintenance Factors
13 June 2019
Constant Light Output (CLO).

Luminous flux factor determinationLuminous flux factor determinationLuminous flux factor determinationLuminous flux factor determination –––– SpecialSpecialSpecialSpecial
case: Constant light output (CLO)case: Constant light output (CLO)case: Constant light output (CLO)case: Constant light output (CLO)
Luminaires utilizing constant light output techniques constantly adjust the luminous
flux based on the known or predicted depreciation behaviour of the light source to
enable a constant luminous flux over time. This functionality needs to be captured in
the determination of the luminous flux factor, fLF.
The CLO feature is realized by initially dimming the light source to the predicted end-of-
life luminous flux and steadily increasing the current (and as such the power
consumption) over time to compensate for the depreciation in luminous flux due to
ageing of the light source.
• NOTE 1The increasing power consumption over time also has an effect on the
electrical design and energy calculations for the installation, but is also a factor when
comparing different CLO and non-CLO luminaires.
• NOTE 2 In the context of this TS, CLO refers to the stand-alone feature based on
known or predicted depreciation and does not include external input such as sensors.
As such, it only applies to the luminous flux factor, fLF.
• .

Next Slide illustrates the behaviour of a CLO luminaire during operation,
however in practice, there are two ways CLO luminaires specifications are
provided by manufacturers. Depending on which of the two options is used,
the luminous flux factor, fLF, shall be determined differently. The current
known options are:
• The standard (non-CLO) specifications are specified (in which case the CLO
correction needs to be done in the maintenance factor using the luminous
flux factor as specified);
• The corrected luminous flux is given (in which case no CLO correction is
needed as this is already represented in the corrected luminous flux, fLF =
1,00).
If the replacement interval is longer than the given CLO lifetime, the manufacturer shall
be consulted for the luminous flux factor, fLF, at the time of replacement.
• .

0
0
1 0 2 0 3 0 4 0 5 0 6 0
2 0
4 0
6 0
8 0
1 0 0
1 2 0
0
0
1 0 2 0 3 0 4 0 5 0 6 0
2 0
4 0
6 0
8 0
1 0 0
1 2 0
Y
X
Y
B
C
A
E
FD
1
2
1
2
X
a) Standard, non-CLO luminaire behaviour (simplified) b) CLO luminaire behaviour (simplified)
Figure 1b) shows a simplified representation of the same luminaire as on left side,
but with CLO functionality. Both power and luminous flux start at 20 % below their
maximum output at 0 h (based on standard operation where total luminous flux
depreciation is 20 % at the end of life - point D). Over time, the luminous flux is kept
constant (line between point D and F), by increasing the power (line between point
D and E). Note that at the end of life, both the standard and the CLO product have
the same power consumption (B versus E) and same luminous flux (C versus F).

Does our Lighting
industry have its
own version
VW
DieselGate

IES files
SP Ratio values
Absolute Photometry
= -1

Design using “Absolute” Photometry
[TESTLAB] ORANGETEK TAIWAN BRANCH
[ISSUEDATE]
[MANUFAC] ORANGETEK
[LUMINAIRE] 36S1x0571N2xxx
[LAMP] OSRAM SQUARE CRI70
[SPR]1.78
TILT=NONE
1 -1 1.80197 181 37 1 2 0.19 0.19 0

Design using “Relative” Photometry
[TESTLAB] ORANGETEK TAIWAN BRANCH
[ISSUEDATE]
[MANUFAC] ORANGETEK
[LUMINAIRE] 36S1x0487N2xxx
[LAMP] OSRAM SQUARE CRI70
[SPR]1.78
TILT=NONE
1 8810 1.804967 181 37 1 2 0.19 0.19 0

ILP - Overall Efficiency
The Overall Efficiency will allow the typical performance of
two luminaires to be compared including all relevant factors
including initial LED flux, LED lumen depreciation, LED survival
rates thermal management and optical efficiency.
The Overall Efficiency shall be the Maintained Luminous Flux
divided by the Average CLO Power Consumption of the
complete luminaire determined as follows:

Overall Efficiency
The maintained luminous flux and average CLO power consumption
of the luminaire measured with the luminaire drive current greater
than or equal to 700mA to each high-power LED or 100mA drive
current to each mid-power LED regardless of the circuit architecture
being series, parallel, ladder, or series parallel.
The Average CLO Power consumption of the complete luminaire
using the Elexon guidance on determining the CLO power, using a
straight-line power increase between the initial power and end of life
power, including driver losses.

Overall Efficiency
Maintained luminaire flux shall be measured using the following procedure:
• Initial Luminous Flux of the complete luminaire (including optics and any diffuser,
bowl or glass front) shall be measured on a goniophotometer or an integrating sphere
with the drive current set at the designated nominal value and the CLO factor set at
100% representing the end of life power consumption condition.
• Testing shall be completed at ambient air temperature, Ta = 25˚C.
• The Initial Luminous Flux multiplied by the BS 5489-1 (LLMF x LSF) elements of the
maintenance factor to give the Maintained Luminous Flux at end of life.
• LLMF based on IES TM-21 prediction using the nearest higher temperature curve to
the LED reference (solder point or junction) temperature taken from the In-Situ
Temperature Measurement Test at ambient air temperature, Ta=25˚C.
• LSF taking account of both the number of LED failures expected during the life of the
luminaire (use actual figures where available but no less than the greater of 3% of
LEDs or one LED failure per LED module).
• The effects of the LED module circuit architecture taken into account when assessing
the impact of a single LED failure on the performance of a luminaire. This may result
in adverse drive current distribution around the circuit, leading to sequential failure of
further LEDs or in the worst case, the whole circuit board going out of light.

If not, then we need a WatchDog

13 June 2019
Recommendations:
The methodology in BS PD ISO/CIE TS 22012: 2019 is the best practice approach for
calculation of maintenance factors for LED luminaires.
The guidance in BS EN 62717 and BS EN 62722 is not suitable for the calculation of
maintenance factors for any luminaires.
Lx By should not be specified for the performance over the rated life of a luminaire as the
methods in BS EN 62717 and BS EN 62722 relate to the performance at the end of the test
period not the end of the rated luminaire life. The average/median useful life, Lx (Lx B50)
shall be used for calculating maintenance factors.
A standard method is presented for calculating the Overall Efficiency of the luminaire.
This method outlines a testing and calculation method using standardised methods and
co-ordinated operating parameters to ensure performance and overall efficiency claims
for luminaires are reliable and should be adopted.

Maintenance Factors
13 June 2019
Thanks for Listening

CLO 100,000hr rated life
50%
60%
70%
80%
90%
100%
110%
0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000 110000
CLO L80 100k rated life
power lumen
50%
60%
70%
80%
90%
100%
110%
0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000 110000
CLO L92 100k rated life
power lumen

Non CLO 100,000 hours
50%
60%
70%
80%
90%
100%
110%
0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000 110000
Non CLO L92
power lumen
50%
60%
70%
80%
90%
100%
110%
0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000 110000
Non -CLO L80
power lumen

PLS 2019: Maintenance factors update – review of the new ILP Guidance Note and the ISO/CIE recent report

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PLS 2019: Maintenance factors update – review of the new ILP Guidance Note and the ISO/CIE recent report