Light and lighting -- Maintenance factor determination -- Way of working

This document specifies a standardized way of working for determining the maintenance factor for both outdoor and indoor lighting installations using the methodology as described in CIE 154:2003 and CIE 097:2005.

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TECHNICAL ISO/CIE TS
SPECIFICATION 22012
First edition
2019-02
Light and lighting — Maintenance
factor determination — Way of
working
Reference number
ISO/CIE TS 22012:2019(E)
ISO/CIE 2019
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ISO/CIE TS 22012:2019(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO/CIE 2019

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

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Published in Switzerland
ii © ISO/CIE 2019 – All rights reserved
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ISO/CIE TS 22012:2019(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols and units ............................................................................................................................................................................................... 3

5 Influencing factors .............................................................................................................................................................................................. 4

5.1 Luminaire and/or light source characteristics............................................................................................................ 4

5.2 Recoverable external factors ....................................................................................................................................................... 4

5.3 Non-recoverable external factors ........................................................................................................................................... 4

5.4 Maintenance period, cleaning, replacement and surface refurbishment interval ........................ 4

6 Maintenance factor determination ................................................................................................................................................... 5

6.1 Basic description of the method .............................................................................................................................................. 5

6.2 Luminous flux factor .......................................................................................................................................................................... 5

6.2.1 Luminous flux factor determination — General................................................................................... 5

6.2.2 Luminous flux factor determination — Special case: Constant light output (CLO) 6

6.3 Survival factor .......................................................................................................................................................................................... 8

6.3.1 Survival factor description ...................................................................................................................................... 8

6.3.2 Spot replacement regime ......................................................................................................................................... 8

6.3.3 Group replacement regime ..................................................................................................................................... 8

6.3.4 Regime combinations .................................................................................................................................................. 9

6.4 Luminaire maintenance factor .................................................................................................................................................. 9

6.4.1 Luminaire maintenance factor description .............................................................................................. 9

6.4.2 Indoor luminaires ........................................................................................................................................................10

6.4.3 Outdoor luminaires ....................................................................................................................................................10

6.5 Surface maintenance factor ......................................................................................................................................................10

7 Use of the maintenance factor .............................................................................................................................................................10

7.1 Lighting design using the maintenance factor ..........................................................................................................10

7.2 Documentation ....................................................................................................................................................................................11

7.2.1 Documentation of maintenance factor determination ................................................................11

7.2.2 Documentation of maintenance schedules ............................................................................................11

7.3 Lighting verification using the maintenance factor .............................................................................................11

Annex A (informative) Maintenance factor determination examples ............................................................................13

Annex B (informative) Luminous flux factor f tables (Typical examples) .............................................................17

Annex C (informative) Luminaire maintenance factor f determination examples .....................................19

Annex D (informative) Surface maintenance factor f examples .....................................................................................24

Bibliography .............................................................................................................................................................................................................................28

© ISO/CIE 2019 – All rights reserved iii
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ISO/CIE TS 22012:2019(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see

www .iso .org/iso/foreword .html.

ISO collaborates closely with the International Commission on Illumination (CIE) on all matters of

standardization for light and lighting.

This document was prepared by Technical Committee ISO/TC 274, Light and lighting. The document has

been jointly prepared with CIE JTC 11, Light and Lighting — Maintenance factor — Way of working.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO/CIE 2019 – All rights reserved
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ISO/CIE TS 22012:2019(E)
Introduction

Continuous maintenance of lighting installations is essential as it ensures that the performance

of a system stays within the design limits and promotes safety and efficient use of energy. In the

design phase this is taken into account through the use of the maintenance factor. The maintenance

factor combines several different factors such as the assumed product/installation behaviour, the

environmental parameters and maintenance and cleaning schedules.

The methodology of determining the maintenance factor has been extensively documented by CIE

(see Clause 2 and bibliography). However, as the focus of these technical reports was predominantly

on incandescent and gas discharge light sources, more clarity is needed to ensure the proper use/

translation of the existing methodology towards technologies such as light emitting diodes (LED).

Technologies such as LED distinguish themselves from other technologies by their long lifetime, low

failure rate and their integration of components which were previously seen as separate components.

As such the previous methods used to determine the depreciation and survival of luminaires might

seem unusable and cause uncertainty. However, based on work by IEC (see Clause 2) the luminous flux

depreciation and light source failure parameters have now been (re)established for LED-based light

sources and allow for translation into an updated way of working to determine the maintenance factor

using the existing CIE methodology and data for luminaire and surface dirt depreciation.

This document combines insights from IEC standards with regard to product performance of luminaires

and light sources currently in the market with the existing determination methodology from CIE

Technical Reports. Furthermore, it references the data in the CIE Technical Reports with regard to the

impact of the environment on luminaires (accumulation of dirt on surfaces and luminaires).

This document provides the following:

— 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.
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TECHNICAL SPECIFICATION ISO/CIE TS 22012:2019(E)
Light and lighting — Maintenance factor determination —
Way of working
1 Scope

This document specifies a standardized way of working for determining the maintenance factor for

both outdoor and indoor lighting installations using the methodology as described in CIE 154:2003 and

CIE 097:2005.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

CIE 097:2005, Maintenance of Indoor Electric Lighting Systems
CIE 154:2003, Maintenance of Outdoor Lighting Systems
CIE S 017, ILV International Lighting Vocabulary

IEC 62722-2-1, Luminaire performance — Part 2-1: Particular requirements for LED luminaires

3 Terms and definitions

For the purposes of this document, the terms and definitions given in CIE S 017 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
abrupt failure value
AFV
percentage of LED based products failing to operate at median useful life (L )
[SOURCE: IEC 62717:2014+AMD1: 2015, modified — generalized to products]
3.2
cleaning interval
planned time between cleaning of (parts of) the products and/or components
3.3
CLO lifetime
time over which the CLO (3.5) feature ensures a constant luminous flux
3.4
component replacement interval
planned time between replacement of one or more specified luminaire component(s)
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ISO/CIE TS 22012:2019(E)
3.5
CLO
constant light output

functionality to constantly adjust the luminous flux of the light source based on the known or predicted

depreciation behaviour of the light source to enable a constant luminous flux over time

3.6
failure probability

probability that the component (e.g. light source, luminaire) catastrophically fails

Note 1 to entry: Failure probability is expressed as a factor.
3.7
installation lifetime
time over which the installation is expected to function as designed
3.8
maintenance period
total time over which the maintenance is planned

Note 1 to entry: Within a single maintenance period different maintenance cycles can be planned for different

activities (e.g. cleaning, light source replacement).
Note 2 to entry: The maintenance period is often expressed in years.
3.9
median useful life

length of time until 50 % of a population of operating LED products reaches gradual light output

degradation of a percentage x
3.10
surface refurbishment interval

planned time between surface refurbishment instances where the reflecting properties of the room

or area surfaces are restored to their original state, including cleaning or painting of interior surfaces

such as walls and ceilings

Note 1 to entry: The concept ‘surface refurbishment interval’ does not refer to surfaces which are an integral

part of the luminaire.
3.11
survival probability
probability that a component continues to operate at a certain point in time
Note 1 to entry: Survival probability is expressed as a factor.
Note 2 to entry: The component can be e.g. a light source, a luminaire.

Note 3 to entry: There is a distinct difference between the survival factor (see 6.3) and the survival probability.

The survival probability describes the performance of an individual component whereas the survival factor

describes the outcome of the determination process as described in 6.3.
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ISO/CIE TS 22012:2019(E)
3.12
useful life
x,By

length of time until a percentage y of a population of operating LED luminaires

reaches gradual light output degradation of a percentage x, expressed in general in the ‘L ’ format

x,By

Note 1 to entry: Useful life can be specified on different product levels such as on individual LED, LED module or

LED luminaire level. As for example luminaire design impacts thermal design, the useful life of the LED module

might be different from the useful life of the luminaire.

[SOURCE: IEC 62717:2014+AMD1: 2015, modified — specifier and quantity symbol

added to the term]
4 Symbols and units
The symbols and units in Table 1 apply.
Table 1 — Symbols and units
Symbol Term Unit
E measured illuminance lx
E corrected measured illuminance lx
A,c
E maintained illuminance lx
E initial illuminance lx
f luminous flux factor (see 6.2) 1
f lamp luminous flux maintenance factor 1
LLM
f luminaire maintenance factor (see 6.4) 1
f maintenance factor (see 6.1) 1
NOTE In this document the term "maintenance factor" is used
for luminaires either with integrated or separate light sources, in
contrast to CIE 97 and CIE 154 where the light source is generally
seen as separate from the luminaire.
f survival factor (see 6.3) 1
f surface maintenance factor (see 6.5) 1
Φ luminaire luminous flux lm
Φ CLO-corrected luminaire luminous flux lm
CLO
Φ standard luminaire luminous flux lm
Φ end-of-life luminaire luminous flux lm
Φ initial luminaire luminous flux lm
L median useful life (see 3.8) for x % remaining luminous flux h
L useful life h
x,By
p failure probability 1
p survival probability 1

1) Note that in the source IEC 62717 the expression "L B " is incorrectly presented as a quantity symbol for

x y

the term "useful life". As such, this document introduces the symbol L for the term “useful life” for use in this

x,By
document and further usage.
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ISO/CIE TS 22012:2019(E)
5 Influencing factors
5.1 Luminaire and/or light source characteristics

Depreciation of the luminaire and/or light source due to regular ageing and/or product-related

characteristics shall be taken into account. This includes the following components:

— luminous flux depreciation (either of the light source or the luminaire, depending on the luminaire

design) (see 6.2);

— light source and/or luminaire catastrophic failure (depending on luminaire design) (see 6.3).

5.2 Recoverable external factors

Recoverable factors concern those external factors, causing depreciation of the lighting installation

performance, of which the effects can be economically reversed or mitigated during service and/or

routine maintenance. The following factors shall be taken into account:
— removable pollution in/on the luminaire (see 6.4);

— depreciation of room or area surface characteristics relevant to the lighting installation (i.e.

reduction of reflectance due to degradation of walls or ceiling finishes) (see 6.5).

5.3 Non-recoverable external factors

Influencing external factors are classified as non-recoverable when they are caused by external

(environmental) factors and cannot be reversed during normal maintenance or are uneconomical

to restore. These factors include the ageing/fading of (non-replaceable) components due to the

environmental conditions and/or the irreversible soiling of components in applications due to specific

(aggressive) substances.

Although these factors should be taken into account during the design and maintenance planning phase,

they are not included in the maintenance factor as described in this document.
5.4 Maintenance period, cleaning, replacement and surface refurbishment interval

The choice of maintenance period, cleaning and replacement interval has a large impact on the

maintenance factor. Prior to determination of the maintenance factor, the following information shall

be determined:
— maintenance period (often expressed in years);
— cleaning interval of luminaires (often expressed in years);
— component replacement interval (often expressed in burning hours) and
— surface refurbishment interval (often expressed in years).
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ISO/CIE TS 22012:2019(E)
6 Maintenance factor determination
6.1 Basic description of the method
The maintenance factor f is determined using the Formula (1).
ff=⋅ ff⋅⋅ f (1)
m LF SLMSM
where
f is the luminous flux factor (see 6.2);
f is the survival factor (see 6.3);
f is the luminaire maintenance factor (see 6.4);
f is the surface maintenance factor (see 6.5).
Annex A provides examples demonstrating the determination of these factors.

NOTE The methodology described in this document is a replacement of the methodology as described

in CIE 097:2005 and CIE 154:2003. Terminology has been changed to suit a more generalized approach for

luminaires either with integrated or separate light sources. Terminology changes are further specified in the

relevant paragraphs.
6.2 Luminous flux factor
6.2.1 Luminous flux factor determination — General

The luminous flux factor, f , expresses the depreciation of the luminous flux over time due to ageing of

the light source or luminaire during regular operation (this excludes external factors). This is defined

as the ratio of depreciated luminous flux to the initial luminous flux.

For luminaires with an integrated light source the luminous flux factor, f , shall be determined for the

(full) luminaire. For luminaires with a non-integrated light source the luminous flux factor, f , shall be

determined for the light source (i.e. lamp).

NOTE 1 In CIE 097:2005 and CIE 154:2003 the equivalent of the luminous flux factor, f , is the lamp luminous

flux maintenance factor ( f , abbreviation: LLMF). See Note in 6.1 for further information.

LLM

NOTE 2 The luminous flux factor, f , determined at luminaire level will better reflect reality as this includes

all components and operating conditions. Therefore, this is the default method for all types of luminaires.

However, for luminaires with non-integrated light sources it is often not possible to determine this for the full

luminaire as data is only available for the light source and as such the luminous flux factor, f , on light source

level is accepted for luminaires with non-integrated light sources.

For LED-based luminaires the luminous flux factor, f , shall be determined based upon the light source

or luminaire replacement interval and shall be provided by the luminaire supplier according to the

definitions in IEC 62722-2-1.

The replacement interval can correspond to the median useful life, L . In this case the luminous flux

factor, f , equals x/100.

EXAMPLE 1 L = 50 000 h translates to 80 % remaining luminous flux at 50 000 h. If the luminaire or light

source is also planned to be replaced at 50 000 h this would result in a luminous flux factor f = 0,80.

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ISO/CIE TS 22012:2019(E)

If the replacement interval is different from the published values, the correct luminous flux factor, f ,

needs to be supplied by the manufacturer. Alternatively, the tables with example values provided in

Annex B may be used as an approximation.

NOTE 3 In some cases the depreciation values are not individually stated, but can be obtained from the

lifetime values which will be presented as the median useful life, L , or the useful life ‘L ’ value. In both cases,

x x,By

only the x value of the L value is relevant for the luminous flux factor determination, the B element of ‘L ’ is

x y x,By

not taken into account in the f and consequently the f determination (e.g. the luminous flux factor f = 0,80

LF m LF
after 50 000 h for both L = 50 000 h and L = 50 000 h specifications).
80,B50 80,B10

NOTE 4 In some cases the depreciation values will be presented as ‘L F ’ values. The ‘L F ’ is a (no longer in

x y x y

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, f ,

and the survival factor, f .

For light sources such as halogen lamps, high pressure sodium lamps, metal halide lamps or fluorescent

lamps, the depreciation of the luminous flux is often provided as a separate characteristic for given

lifetimes.

EXAMPLE 2 If the planned maintenance period is at 16 000 h and the rated lamp luminous flux maintenance

factor f provided by the manufacturer at 16 000 h is 0,90, then the luminous flux factor f is 0,90.

LLM LF

NOTE 5 Dimming and/or switching behaviour can have a positive or negative effect on the depreciation of the

light source, but this depends upon the luminaire and/or light source design. Information on these effects can be

requested from the manufacturer of the light source or luminaire.

6.2.2 Luminous flux factor determination — Special 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, f .

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 1 The 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, f . Other systems using external input to correct for depreciation exist but are not a part of this document.

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ISO/CIE TS 22012:2019(E)
EXAMPLE

a) Standard, non-CLO luminaire behaviour b) CLO luminaire behaviour (simplified)

(simplified)
Key
1 Relative power
2 Relative luminous flux
X time in 1 000 h
Y relative output in %
A rated power and luminaire luminous flux for luminaires without CLO, 100 %
B end of useful life power for luminaires without CLO

C end of useful life luminous flux for luminaires without CLO (e.g. for L = 80 %)

D rated power and luminaire luminous flux for luminaires corrected for CLO (e.g. 80 % of maximum for L )

E end of useful life power for luminaires with CLO (100 %)

F end of useful life luminous flux for luminaires with CLO (e.g. 80 % of maximum for L )

Figure 1 — Illustration of CLO principle using simplified graph representations

Figure 1 a) shows a simplified representation of a standard product not using CLO, based on

L = 50 000 h (i.e. 20 % depreciation after 50 000 h). Both power and luminous flux are set to their

maximum value (point A). Over time, power remains the same (line between point A and B) whereas

the luminous flux for a luminaire without CLO depreciates to its end-of-life luminous flux (line between

point A and C, 80 % of luminous flux).

Figure 1 b) 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).

Figure 1 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, f , shall be determined differently. The current known

options are:

1. 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 below);

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ISO/CIE TS 22012:2019(E)
2. the corrected luminous flux is given (in which
...

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