CIE 97：2005

5/23/2018 CIE 97 2005

1/36

ISBN 3 901 906 45 2

GUIDE ON THE MAINTENANCE OFINDOOR ELECTRIC LIGHTINGSYSTEMS

CIE 97:20052nd Edition

UDC: 628.972 Descriptor: Interior lighting628.987 Evaluation of lighting installations

Copyright International Commission on IlluminationProvided by IHS under license with CIE

Not for ResaleNo reproduction or networking permitted without license from IHS

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THE INTERNATIONAL COMMISSION ON ILLUMINATION

The International Commission on Illumination (CIE) is an organisation devoted to international co-operation and exchange ofinformation among its member countries on all matters relating to the art and science of lighting. Its membership consists ofthe National Committees in about 40 countries.

The objectives of the CIE are :1. To provide an international forum for the discussion of all matters relating to the science, technology and art in the

fields of light and lighting and for the interchange of information in these fields between countries.

2. To develop basic standards and procedures of metrology in the fields of light and lighting.3. To provide guidance in the application of principles and procedures in the development of international and national

standards in the fields of light and lighting.4. To prepare and publish standards, reports and other publications concerned with all matters relating to the science,

technology and art in the fields of light and lighting.5. To maintain liaison and technical interaction with other international organisations concerned with matters related to

the science, technology, standardisation and art in the fields of light and lighting.The work of the CIE is carried on by seven Divisions each with about 20 Technical Committees. This work covers subjectsranging from fundamental matters to all types of lighting applications. The standards and technical reports developed bythese international Divisions of the CIE are accepted throughout the world.

A plenary session is held every four years at which the work of the Divisions and Technical Committees is reviewed,reported and plans are made for the future. The CIE is recognised as the authority on all aspects of light and lighting. Assuch it occupies an important position among international organisations.

LA COMMISSION INTERNATIONALE DE L'ECLAIRAGE

La Commission Internationale de l'Eclairage (CIE) est une organisation qui se donne pour but la coopration internationaleet l'change d'informations entre les Pays membres sur toutes les questions relatives l'art et la science de l'clairage.Elle est compose de Comits Nationaux reprsentant environ 40 pays.

Les objectifs de la CIE sont :1. De constituer un centre d'tude international pour toute matire relevant de la science, de la technologie et de l'art de

la lumire et de l'clairage et pour l'change entre pays d'informations dans ces domaines.2. D'laborer des normes et des mthodes de base pour la mtrologie dans les domaines de la lumire et de l'clairage.3. De donner des directives pour l'application des principes et des mthodes d'laboration de normes internationales et

nationales dans les domaines de la lumire et de l'clairage.4. De prparer et publier des normes, rapports et autres textes, concernant toutes matires relatives la science, la

technologie et l'art dans les domaines de la lumire et de l'clairage.5. De maintenir une liaison et une collaboration technique avec les autres organisations internationales concernes par

des sujets relatifs la science, la technologie, la normalisation et l'art dans les domaines de la lumire et del'clairage.

Les travaux de la CIE sont effectus par 7 Divisions, ayant chacune environ 20 Comits Techniques. Les sujets d'tudess'tendent des questions fondamentales, tous les types d'applications de l'clairage. Les normes et les rapportstechniques labors par ces Divisions Internationales de la CIE sont reconnus dans le monde entier.

Tous les quatre ans, une Session plnire passe en revue le travail des Divisions et des Comits Techniques, en faitrapport et tablit les projets de travaux pour l'avenir. La CIE est reconnue comme la plus haute autorit en ce qui concernetous les aspects de la lumire et de l'clairage. Elle occupe comme telle une position importante parmi les organisationsinternationales.

DIE INTERNATIONALE BELEUCHTUNGSKOMMISSION

Die Internationale Beleuchtungskommission (CIE) ist eine Organisation, die sich der internationalen Zusammenarbeit unddem Austausch von Informationen zwischen ihren Mitgliedslndern bezglich der Kunst und Wissenschaft der Lichttechnikwidmet. Die Mitgliedschaft besteht aus den Nationalen Komitees in rund 40 Lndern.

Die Ziele der CIE sind :1. Ein internationaler Mittelpunkt fr Diskussionen aller Fragen auf dem Gebiet der Wissenschaft, Technik und Kunst der

Lichttechnik und fr den Informationsaustausch auf diesen Gebieten zwischen den einzelnen Lndern zu sein.2. Grundnormen und Verfahren der Metechnik auf dem Gebiet der Lichttechnik zu entwickeln.3. Richtlinien fr die Anwendung von Prinzipien und Vorgngen in der Entwicklung internationaler und nationaler Normen

auf dem Gebiet der Lichttechnik zu erstellen.4. Normen, Berichte und andere Publikationen zu erstellen und zu verffentlichen, die alle Fragen auf dem Gebiet der

Wissenschaft, Technik und Kunst der Lichttechnik betreffen.5. Liaison und technische Zusammenarbeit mit anderen internationalen Organisationen zu unterhalten, die mit Fragen

der Wissenschaft, Technik, Normung und Kunst auf dem Gebiet der Lichttechnik zu tun haben.Die Arbeit der CIE wird in 7 Divisionen, jede mit etwa 20 Technischen Komitees, geleistet. Diese Arbeit betrifft Gebiete mitgrundlegendem Inhalt bis zu allen Arten der Lichtanwendung. Die Normen und Technischen Berichte, die von dieseninternational zusammengesetzten Divisionen ausgearbeitet werden, sind von der ganzen Welt anerkannt.Tagungen werden alle vier Jahre abgehalten, in der die Arbeiten der Divisionen berprft und berichtet und neue Plne frdie Zukunft ausgearbeitet werden. Die CIE wird als hchste Autoritt fr alle Aspekte des Lichtes und der Beleuchtungangesehen. Auf diese Weise unterhlt sie eine bedeutende Stellung unter den internationalen Organisationen.

Published by theCOMMISSION INTERNATIONALE DE L'ECLAIRAGE

CIE Central BureauKegelgasse 27, A-1030 Vienna, AUSTRIA

Tel: +43(1)714 31 87 0, Fax: +43(1) 714 31 87 18e-mail: [email protected]

WWW: http://www.cie.co.at/CIE 2005 All rights reserved



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GUIDE ON THE MAINTENANCE OFINDOOR ELECTRIC LIGHTINGSYSTEMS

CIE 97:20052nd Edition

UDC: 628.972 Descriptor: Interior lighting628.987 Evaluation of lighting installations



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This Technical Report has been prepared by CIE Technical Committee 3-40 of Division 3"Interior Environment and Lighting Design" and has been approved by the Board ofAdministration of the Commission Internationale de l'Eclairage for study and application. Thedocument reports on current knowledge and experience within the specific field of light andlighting described, and is intended to be used by the CIE membership and other interestedparties. It should be noted, however, that the status of this document is advisory and not

mandatory. The latest CIE proceedings or CIE NEWS should be consulted regarding possiblesubsequent amendments.

Ce rapport technique a t labor par le Comit Technique CIE 3-40 de la Division 3"Environnement interur et tude de l'clairage" et a t approuv par le Bureau de laCommission Internationale de l'Eclairage, pour tude et emploi. Le document expose lesconnaissances et l'exprience actuelles dans le domaine particulier de la lumire et del'clairage dcrit ici. Il est destin tre utilis par les membres de la CIE et par tous lesintresss. Il faut cependant noter que ce document est indicatif et non obligatoire. Il fautconsulter les plus rcents comptes rendus de la CIE, ou le CIE NEWS, en ce qui concernedes amendements nouveaux ventuels.

Dieser Technische Bericht ist vom CIE Technischen Komitee 3-40 der Division 3 "Innenraumund Beleuchtungsentwurf" ausgearbeitet und vom Vorstand der Commission Internationalede l'Eclairage gebilligt worden. Das Dokument berichtet ber den derzeitigen Stand desWissens und Erfahrung in dem behandelten Gebiet von Licht und Beleuchtung; es ist zurVerwendung durch CIE-Mitglieder und durch andere Interessierte bestimmt. Es sollte jedochbeachtet werden, da das Dokument eine Empfehlung und keine Vorschrift ist. Die neuestenCIE-Tagungsberichte oder das CIE NEWS sollten im Hinblick auf mgliche spterenderungen zu Rate gezogen werden.

Any mention of organisations or products does not imply endorsement by the CIE. Whilstevery care has been taken in the compilation of any lists, up to the time of going to press,these may not be comprehensive.

Toute mention d'organisme ou de produit n'implique pas une prfrence de la CIE. Malgr lesoin apport la compilation de tous les documents jusqu' la mise sous presse, ce travailne saurait tre exhaustif.

Die Erwhnung von Organisationen oder Erzeugnissen bedeutet keine Billigung durch dieCIE. Obgleich groe Sorgfalt bei der Erstellung von Verzeichnissen bis zum Zeitpunkt derDrucklegung angewendet wurde, ist es mglich, da diese nicht vollstndig sind.

CIE 2005 All rights reserved

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The following members of TC 3-40, "Maintenance of indoor electric lighting systems" tookpart in the preparation of this technical report. The committee comes under Division 3 "InteriorEnvironment and Lighting Design". This guide replaces CIE 97-1992 "Maintenance of indoorelectric lighting systems".

Members of the Technical Committee were:

Bedocs, L. UK, chairDehoff, P. Austria

Di Fraia, L. Italy

Henderson, R. Republic of South Africa

Julian, W. Australia

Juslen, H. Finland

Kaplan, H. USA

Katayama, S. Japan

Lillelien, E. Norway

Schierz, C. Switzerland

Stockmar, A. Germany

Vonnak, I. Hungary

Wisniewski, A. Poland

Zonneveldt, L. The Netherlands

The CIE acknowledges the contribution from the following for the supply of lamp data:

GE Osram Philips SLI

III



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CONTENTS

SUMMARY VRESUME VZUSAMMENFASSUNG V1. INTRODUCTION 12. NEED FOR MAINTENANCE 1

2.1 Influencing factors 22.1.1 Non-recoverable factors 22.1.2 Recoverable factors 3

2.2 Inspection intervals and cleanliness category 32.3 Cleaning schedule 4

3.ANALYSIS OF DEPRECIATION 53.1 Lamp lumen maintenance factor 53.2 Lamp survival 6

3.2.1 Differences between lamp types 73.2.2 Differences within one lamp type 83.2.3 Differences by external influence on lamp 8

3.3 Circuits and controls 83.4 Luminaire maintenance factor 93.5 Room surface maintenance factor (RSMF) 11

4. MAINTENANCE FACTOR 174.1 Determination of maintenance factor 174.2 Use of maintenance factor (MF) 174.3 Designing out maintenance 184.4 Sustainability 19

5. ECONOMICS OF SERVICING 195.1 Lamp replacement 195.2 Cleaning of luminaires 205.3 Maintenance programmes 215.4 Equipment and installation 21

6. SERVICING LIGHTING SYSTEMS 226.1 Access 226.2 Cleaning luminaires 226.3 Cleaning agents 226.4 Re-lamping 23

7. REFERENCES 238.APPENDICES 24

8.1 Example of maintenance factor estimation 248.2

Example of luminaire cleaning interval estimation 24

8.3 Equipment for maintenance 25

8.3.1 Ladders 258.3.2 Scaffolding 258.3.3 Telescopic scaffolding 268.3.4 Lift truck or hoist 268.3.5 Disconnecting hangers (raising and lowering devices) 268.3.6 Lamp changers 268.3.7 Catwalks, cranes, cages, etc. 268.3.8 Vacuum cleaners and blowers 268.3.9 Wash tanks 268.3.10 Ultrasonic cleaning 26

8.4 Terminology 278.5 Bibliography 27

IV



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GUIDE ON THE MAINTENANCE OF INDOOR ELECTRIC LIGHTING SYSTEMS

SUMMARY

During the life of a lighting installation, the light available for the task progressively decreasesdue to accumulation of dirt on surface and aging of equipment. The rate of reduction isinfluenced by the equipment choice and the environmental and operating conditions. Inlighting scheme design we must take account of this fall by the use of a maintenance factorand plan suitable maintenance schedules to limit the decay. Lighting standard "ISO 8995/CIES 008-2001 Lighting of Indoor Workplaces" in Section 4.8, recommends a minimummaintenance factor. It states that "The lighting scheme should be designed with overallmaintenance factor calculated for the selected lighting equipment, space environment andspecified maintenance schedule". A high maintenance factor together with an effectivemaintenance programme promotes energy efficient design of lighting schemes and limits theinstalled lighting power requirements.

This revision of the guide describes the parameters influencing the depreciationprocess and develops the procedure for estimating the maintenance factor for indoor electriclighting systems. It provides information on the selection of equipment and the estimation ofeconomic maintenance cycles and gives advice on servicing techniques. It shows some

examples of data but for accurate data it recommends that data should be obtained from themanufacturers.

GUIDE SUR LA MAINTENANCE DES INSTALLATIONS DECLAIRAGE INTERIEUR

RESUME

Pendant la dure de vie dune installation dclairage, la lumire disponible sur la tchevisuelle dcrot de manire progressive en raison de laccumulation de poussires sur lessurfaces et du vieillissement de linstallation. Cest le choix des quipements, les conditionsde fonctionnement et la nature de lenvironnement qui ont une incidence sur le taux derduction de lclairage. La prise en compte de cette dprciation est faite au moyen du

facteur de maintenance et du plan de maintenance programm pour en limiter leffet. Lanorme dclairage ISO 8995/CIE S 008-2001 - Eclairage intrieur pour des lieux de travailrecommande, au paragraphe 4.8, une valeur minimale du facteur de maintenance; le projetdclairage doit tre conu sur la base dun facteur de maintenance global dfini suivantlquipement dclairage choisi, les conditions environnementales et le programme demaintenance retenu. Un facteur de maintenance lev, associ un programme demaintenance spcifique, contribue raliser des projets dclairage efficaces sur le plannergtique et rduire les exigences de la puissance installe en clairage.

La rvision de ce guide dcrit les paramtres qui ont une incidence sur le processus dedprciation et dvelope les mthodes dvaluation du facteur de maintenance desinstallations dclairage intrieur. Il fournit des informations pour la slection desquipements, lvaluation conomique des cycles de maintenance et les indications sur les

techniques dentretien. Des exemples sont cits, avec la recommandation de consulter lesfabricants pour des applications particulires.

LEITFADEN ZUR WARTUNG VON ELEKTRISCHEN BELEUCHTUNGSANLAGEN IMINNENRAUM

ZUSAMMENFASSUNG

Wegen Verschmutzung und Alterung nimmt die fr die jeweilige Aufgabe verfgbareLichtmenge whrend der Lebensdauer einer Beleuchtungsanlage stndig ab. DieAbnahmerate wird sowohl durch die Wahl der Anlage als auch durch Umwelt- undBetriebsbedingungen beeinflusst. Um diesen Lichtabfall zu begrenzen, ist er bei derBeleuchtungsplanung mittels eines Wartungsfaktors zu bercksichtigen und es mssengeeignete Wartungsplne festgelegt werden. Die Beleuchtungsnorm "ISO 8995/CIE S 008-2001 Beleuchtung von Arbeitspltzen in Innenrumen" empfiehlt in Abschnitt 4.8 einenminimalen Wartungsfaktor. Es heit dort: Die Beleuchtungsanlage sollte mit einem alle

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Einflsse bercksichtigenden Wartungsfaktor geplant werden, der fr die vorgeseheneBeleuchtungseinrichtung, die rumliche Umgebung und den festgelegten Wartungsplanerrechnet wurde. Ein hoher Wartungsfaktor zusammen mit einem wirksamenWartungsprogramm frdert die Planung von energieeffizienten Beleuchtungsanlagen undbegrenzt den Bedarf an installierter elektrischer Energie.

Dieser berarbeitete Leitfaden beschreibt die Parameter, welche denWertminderungsprozess beeinflussen und erschliet das Verfahren zur Schtzung desWartungsfaktors fr elektrische Beleuchtungsanlagen im Innenraum. Er bietet Hilfe bei derWahl von Gerten und beim Ausarbeiten von wirtschaftlichen Wartungszyklen und gibtAuskunft ber Wartungstechniken. Der Leitfaden zeigt zwar einige beispielhafte Daten,empfiehlt aber, fr genauere Werte die Herstellerangaben zu verwenden.

VI



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1. INTRODUCTION

Maintenance of all lighting installations is essential as it keeps the performance of the systemwithin the design limits and promotes safety and efficient use of energy. It is a fact that thelighting level provided by a lighting installation will decrease gradually throughout the life ofthe installation. Several terms have been used to describe the factor that accounts for thisreduction but in this guide throughout the term Maintenance Factor is used. The equivalentterm in French is "Facteur de dprciation".

Maintenance factor is defined as the "ratio of the average illuminance on the workingplane after a certain period of use of a lighting installation to the initial average illuminanceobtained under the same conditions for the installation therefore taking account of all lossesincluding lamp lumen maintenance.

Notes:

1. The term "light loss factor", having the same definition as maintenance factor, hasbeen used in the past.

2. The term "depreciation factor" has been formerly used to designate the reciprocal ofthe above ratio.

3. The light losses take into account the depreciation caused by dirt accumulation onlamps, luminaires and room surfaces.

4. The CIE S 0082001 Standard on "Lighting of Indoor Workplaces" recommendsthat the designer of the lighting scheme states the maintenance factor, assumptionsand the required maintenance schedule.

The recommended illuminance for lighting design is now based on "maintainedilluminance" which is the average illuminance at a "certain period" of use when maintenancehas to be carried out and is given by,

Emaintained = Einitial Maintenance Factor

Lighting systems have different maintenance characteristics and this should be one ofthe important assessments made in the early stages of project design.

This guide discusses the various influencing factors and gives data based on practicalsolutions that enable the maintenance factor for types of systems, buildings and locations tobe derived. The derived maintenance factor should be applied to all formulae used for lightingscheme calculations, such as illuminance, luminance on areas or at points. Methods forestimating economic maintenance periods and advice on cleaning techniques are also given.

The guide also provides a limited selection of typical current data to allow thecalculation methods to be explained. The examples of data have been updated with newlamp types, luminaire types and improvements in the interior cleanliness. A "very clean"environment category has been added and a new method with data extending to 6 years isproposed for the room surface maintenance factor. However, to take advantage of thecontinuing developments of lighting products and techniques, "up-to-date" data should be

obtained from manufacturers.The bibliography contains a short list of publications used as the basis for this guide

where further information may be obtained.

2. NEED FOR MAINTENANCE

All lighting schemes within a building will deteriorate progressively from the moment they areput into use. The losses are due to the accumulation of dust and dirt on all exposed surfacesof lamps, luminaires and room surfaces - reducing the transmittance or reflectance - and tothe decay in lamp lumen output, failing lamps and aging of surfaces. If this process isunchecked, it will result in the illuminance falling to very low values as shown in Figure 2.1,and the scheme could become very energy inefficient, unsightly and dangerous. As the decayin illuminance is gradual, the workers may not notice the loss immediately. But over a periodthis gradual reduction will cause increased visual strain, more errors and mistakes in thework; the task will take longer to complete and accidents may occur.

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Regular maintenance is, therefore, most important for an effective lighting installation.The lighting system should not only be cleaned correctly and thoroughly but the cleaningshould be carried out at regular intervals. A well-designed maintenance schedule andprogramme will yield a higher maintenance factor and will maintain the required illuminance,reduce capital and operating costs, reduce the installed power requirements and run thesystem safely. It will ensure satisfactory appearance and comfort for the occupants.

However, even with a well-designed and operated maintenance programme some lossof illuminance is inevitable. This loss has to be estimated, at the time the lighting scheme isplanned, and an allowance in the form of maintenance factor should be included in thescheme design calculations.

RelativeIllum

inance(%)

kHours2.5 5.0 7.5 10.0 12.5 15.0 17.5

100

80

60

40

20

100

80

60

40

20Relativeilluminance(%)

A

B

C

D

7654321 Years

MF Scheme

1stluminaireclean

2ndluminaireclean

3rdluminaireclean

1strelam

1stroom

p surfaceclean

AB

non-recoverable

lossesnon-recoverablelosses

MFschemeC

D

1stroomsurfaceclean

2ndluminaireclean

1stluminaireclean

3rdluminaireclean

1strelamp

2,5 5,0 7,5 10,0 12,5 15,0 17,5 khours1 2 3 4 5 6 7 years

Fig. 2.1.Variation of illuminance through life (Linear fluorescent lamp in industrial reflectorluminaire operated with spot lamp replacement programme).

A room surface maintenance curve (reflectance 70/50/20, DFF0,0 in cleanenvironment);

B lamp lumen maintenance curve (HF linear tri-phosphor fluorescent lamp) ;

C luminaire maintenance curve (type C luminaire in clean environment) ;

D un-maintained system output;

MFscheme is the design maintenance factor and indicates the relative maintainedilluminance.

Note: The lamp survival rate is not included as in this case between bulk re-lamping spot

replacement is assumed.

2.1 Influencing factors

There are several factors that can reduce the light output. These are grouped under non-recoverable and recoverable depreciations.

2.1.1 Non-recoverable factors

Non-recoverable factors (NRF), such as ageing/fading of materials, operating temperatureand voltage are inherent in the installation and its environment and cannot be improvedduring normal maintenance or are uneconomical to overcome. These factors in general aresmall (

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Once the non-recoverable reductions, by ageing or soiling, have occurred they cannotbe brought back to their original condition and replacement of the luminaire may benecessary. This is the case with luminaires if they are in, say, dusty or oily atmospheres sothat dust or oil particles become burnt onto the reflector. In such cases it is not economicallyviable to bring the reflector back to its original condition and, therefore, it is advisable(sometimes essential) to replace the reflector. If this is not done the lighting installation will

not provide the maintained illuminance.If the influence of other factors such as voltage, frequency, temperature and ballast,

are permanent and significant then at the design stage the magnitude of these effects shouldbe estimated and an allowance similar to the maintenance factor should be made in thecalculations. These factors although important are not part of this publication and are notused in the described methods. However, it is worth stating that the influence of randomoccurrences may be ignored, provided they do not harm the operation of the lighting system.

2.1.2 Recoverable factors

Recoverable factors, of lamp lumen maintenance, lamp survival, luminaire maintenance,room surface maintenance can be made good during service and routine maintenance.These should be defined in the maintenance schedule and implemented by re-lamping,

cleaning, replacing failed components or painting of the surfaces.

The value of such maintenance programme is indicated by an example in Figure 2.1.This clearly shows that the illuminance in the un-serviced scheme will fall to 50 % of the initialvalue within 6 years and will continue to decline albeit at reduced rate. But by implementing aprogramme of bi-annual luminaire cleaning and 6 yearly bulk re-lamping and room surfacecleaning the decline is checked and can be restored to over 98 % of the initial value. At thistime the maintained scheme provides double of the illuminance of that given by theunmaintained system. The maintenance programme will yield a Maintenance Factor of 0,70for the scheme.

2.2 Inspection intervals and cleanliness category

Regular inspection of lighting installations is advisable. In some countries the provision ofadequate illuminance for working is required by law. Independent inspectors enforce the taskilluminance.

As a guide for those who have their lighting inspected and/or measured, Table 2.1shows maximum time intervals between inspections of various areas. Table 2.1 also indicatesthe cleanliness category of typical places of work.

Note: There may be cases, particularly in certain industrial processes area, where theenvironment is exceedingly dirty which are outside the scope of the aboveclassification.

Table 2.1. Recommended inspection intervals of lighting systems in different workingenvironments.

Inspection interval Environment Activity or task area

Very Clean (VC)Clean rooms, semi conductor plants,hospital clinical areas*, computercentres3 years

Clean (C) Offices, schools, hospital wards

2 years Normal (N)Shops, laboratories, restaurants,warehouses, assembly areas,workshops

1 year Dirty (D)Steelworks, chemical works,foundries, welding, polishing,

woodwork

* For reason of hygiene control, more frequent inspection may be required.

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2.3 Cleaning schedule

To assist operators of maintenance schedules Table 2.2 gives a quick indication of thecleaning intervals for different luminaire types used in the various environments. As far asmaintenance is concerned Table 2.2 and Table 2.3 can also be used as a guide for theselection of luminaires for the particular environments. The data are typical for the luminairesusing any lamp types with the exception of those using high-pressure discharge reflectorlamps. These reflector lamp luminaires will have characteristics similar to type B luminaire.

Table 2.2. Approximate cleaning intervals (marked by X) for luminaires used in variousenvironments.

Cleaning Intervals 3 years 2 years 1 year

Environment

Luminaire type

VCC

N DVCC

N DVCC

N D

A, Bare batten

X X X

B, Open top housing (naturalventilated)

X X X

C, Closed top housing (unventilated)X (X) X

D, Enclosed IP2XX (X) X

E, Dust proof IP5XX X X

F, Enclosed indirect (uplight)

X (X) X

G, Airhandling, forced ventilatedX X X

where VC is very clean, C is clean, N is normal and D is dirty atmosphere in the environment(see Table 2.1).

The selection of intervals is based on having a luminaire maintenance factor (LMF) ofover 0,80.

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Table 2.3. Examples of luminaire types.

Type Luminare types in Table 2.2 Luminaire descriptions

A Bare batten bare lamp luminaires

B

Open top housing(natural ventilated andso called "self cleaning"types)

Direct-indirect luminaires without cover

Direct-indirect luminaires with indirect reflector andclosed optical device

Wallwashing luminaires (vertical opening)

Wall mounted luminaires open top and base

Downlights with open top

CClosed top housing(unventilated)

Recessed and surface mounted luminaires (e.g.with louvers)

Downlights, spotlights

D Enclosed IP2X

General purpose luminaires with closed covers and

optics

E Dust proof IP5X Dust proof IP5X (protected, clean room luminaires)

F Indirect lighting and uplightFree standing, pendent, wall mounted uplighterswith closed base, cove lights

GAir handling and forcedventilated

Air handling body and optic used with air-conditioning or ventilation systems

Luminaires C, D and F are not recommended for dirty environments.

3. ANALYSIS OF DEPRECIATION

Several factors contribute to light losses and the effect and magnitude vary with the type ofactivity and the location. For example, areas vary as to the amount and type of dirt in the air;the amount of dirt in a foundry is greater than that found in an air-conditioned office. But theamount and type of dirt in an office located near an industrial area is different to that for anoffice located in the country. The black dirt found in steel mills is most unlike the relativelylight coloured dust in bakeries. It is important to be able to recognise these variations whenassessing light losses.

3.1 Lamp lumen maintenance factor

Lamp lumen maintenance factor is the relative light output during the lifetime of a burninglamp to the initial output. The light output of all lamp types decreases with burning hours.Table 3.1 gives examples of lamp operating hours (burning hours) for a range of activityareas. The exact rate, however, depends on the specific lamp type and for discharge lampsalso on the ballasting system. The losses due to this effect can be reduced by more frequentlamp replacement, perhaps by group replacement. Table 3.2 shows typical examples of lamplumen maintenance factors. It is therefore very important to obtain up-to-date data from themanufacturers for estimating the maintenance factor and the maintenance programme,particularly when using a new type of lamp.

For accurate data always consult the manufacturer.

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Table 3.1. Typical annual operating hours (burning hours).

Activity Period of occupancyDaylight link

controlsOperating

hours

Include shifts No. of days Hours/day Yes/No * Hours/year

Industrial

Continuous 365 24 no 8760

Process 365 24 yes 7300

Two shifts 310 16 no 4960

Six days/week 310 16 yes 3720

Single shift 310 10 no 3100

Six days/week 310 10 yes 1760

Single shift 258 10 no 2580

Fivedays/week

258 10 yes 1550

Retail

Six days/week 310 10 no 3100

Offices

258 10 no 2580Fivedays/week 258 10 yes 1550

Schools

190 10 no 1900Fivedays/week 190 10 yes 1140

Hospital

365 16 no 58407days/week

365 16 yes 3504

*Assuming adequate daylight is available during daytime for about half the working days. Asdaylight penetration varies across the areas the switching or dimming arrangements will needto be organised accordingly.

Note: Frequent switching of the lamps will reduce the lamp life, see Figure 3.2.

3.2 Lamp survival

Lamp survival factor is the probability of lamps continuing to operate for a given time. Itindicates the percentage of a large representative group of a type of lamp remainingoperational after a certain period. The survival rate depends on lamp type and particularly, inthe case of discharge lamps, the frequency of switching and the ballasting system.Traditionally the lamp life is the declared time in hours when 50% of the lamps in test batchhave survived (see Figure 3.1). Failed lamps in schemes will cause reduction in illuminanceand uniformity, but the effect can be minimised by spot replacement of lamps. Table 3.2shows typical examples of lamp survival data. The LSFvalue should be used in conjunctionwith the LLMFvalue to establish an economic working life for the lamp as the declared life isoften much longer than the economic light output lamp life.

For accurate data consult the manufacturer.

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50% survival (claimed life)

Survivinglamps(%)

% of average life

010

80

60

40

20

10020 40 80 120 140 1660 0

100

80

60

40

20

Survivinglamps(%)

50% survival (claimed life)

20 40 60 80 100 120 140 160

% of average life

Fig. 3.1.Typical lamp mortality curves (statistical group of linear fluorescent lamps on 8switch cycles per 24 hours).

Table 3.2. Typical examples of the lamp lumen maintenance factor (LLMF) and the lampsurvival factor (LSF) data.

It is always advisable to consult manufacturers for detailed and up-to date lamp data.

differences1 0,1 0,5 1 2 4 6 8 10 12 15 20 30

LLMF moderate 1,00 0,97 0,93LSF big 1,00 0,98 0,50LLMF big 1,00 0,99 0,97 0,95

LSF big 1,00 1,00 0,78 0,50LLMF moderate 1,00 0,99 0,98 0,97 0,93 0,92 0,90 0,90 0,90 0,90 0,90LSF moderate 1,00 1,00 1,00 1,00 1,00 0,99 0,98 0,98 0,97 0,94 0,50LLMF moderate 1,00 0,99 0,98 0,97 0,93 0,92 0,90 0,90 0,90 0,90LSF moderate 1,00 1,00 1,00 1,00 1,00 0,99 0,98 0,98 0,92 0,50LLMF moderate 1,00 0,98 0,96 0,95 0,87 0,84 0,81 0,79 0,77 0,75LSF moderate 1,00 1,00 1,00 1,00 1,00 0,99 0,98 0,98 0,92 0,50LLMF big 1,00 0,98 0,97 0,94 0,91 0,89 0,87 0,85LSF big 1,00 0,99 0,99 0,98 0,97 0,94 0,86 0,50LLMF moderate 1,00 0,99 0,97 0,93 0,85 0,82 0,80 0,79 0,78 0,77 0,76LSF moderate 1,00 1,00 0,99 0,98 0,97 0,94 0,90 0,86 0,79 0,69 0,50LLMF big 1,00 0,98 0,95 0,90 0,87 0,83 0,79 0,65 0,63 0,58 0,50LSF big 1,00 0,99 0,99 0,98 0,97 0,92 0,86 0,80 0,73 0,66 0,50LLMF big 1,00 0,95 0,87 0,75 0,72 0,68 0,64 0,60 0,56LSF big 1,00 0,99 0,99 0,98 0,98 0,98 0,95 0,80 0,50LLMF moderate 1,00 1,00 0,98 0,98 0,98 0,97 0,97 0,97 0,97 0,96 0,94 0,90LSF moderate 1,00 1,00 1,00 1,00 0,99 0,99 0,99 0,99 0,97 0,95 0,92 0,50

LLMF bigLSF big

Indicates differences in LLMFand LSFamong lamps, which belong to the same lamp type category2Differences in group of metal halides are extremely remarkable. Very high and very low wattage lamps live

significantly shorter than values given here.3Data of LED's is changing rapidly and no values can be given.

LED3

Burning hours in thousand hours

Flourescent tri-

phosphorFlourescent

halophosphate

Compact fluorescent

Incandescent

HalogenFluorescent tri-

phosphor

Mercury

Data is changing too rapidly.Data is changing too rapidly.

Metal halide (250/400

W)2

Ceramic metal halide

(50/150 W)High pressure sodium

(250/400 W)

Many factors influence the lamp lumen maintenance factor and the lamp survival factor.

3.2.1 Differences between lamp types

Different lamp types behave differently. For example the working principles of anincandescent lamp is a glowing filament whilst a fluorescent lamp is by arc discharge

combined with phosphor emission.

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3.2.2 Differences within one lamp type

Even if the principle working of the lamp type is identical this does not mean that the lampmaintenance characteristics are the same. For example, manufacturers produce severaltypes of halogen lamps for different purposes and the 50% survival rate varies between1000 h and 5000 h.

3.2.3 Differences by external influence on lamp

Many external issues like burning position, environmental conditions, ballasting system,frequency of switching, etc. significantly influence the maintenance characteristics of lamps.

3.3 Circuits and controls

Except the mains voltage rated incandescent lamps all other lamp types require some form ofcontrol gear (ballast or transformer) to provide for voltage match or limiting lamp current.Some lamps particularly compact fluorescent types have this control gear integral (built in)and are disposed at the end of lamp life. However, the majority of lamps use remote controlgear that last several lamp changes. For safe and reliable operation during lamp change it isimportant to ensure that the replacement lamp is compatible with the control gear. The

manufacturers of luminaires use both magnetic and electronic control gear and they shouldbe consulted on the choice. The control gear may be fixed or variable (dim) output and can becoupled with lighting management systems. These systems can be linked to timed control orpeople presence detection and/or daylight sensing to switch or dim the lamps accordingly. Asmentioned in Section 3.2 the lamp life is based on defined frequency of switching within a24 hour period. Frequent switching will reduce lamp life (see Figure 3.2). Studies have shownthat correct dimming of lamps has no adverse effect on lamp life, in fact incandescent lampscan benefit. Fig 3.2 and Table 3.3 give examples of how ballasting system and switchingfrequency influence the lifetime of linear fluorescent lamps.

The effect of switching on lamp life

0

50

100

150

200

250

300

0 1 2 4 6 8 10 12 18 24 36 48

Nu

The effect of switching on lamp life

Percentageofratedlife%

Percentageofratedlife%

mber of switching in 24 hrsNumber of switching in 24 hrs

Fig. 3.2.Example of the effect of switching on lamp life for fluorescent lampon lagging switch start circuit.

Note: The glow switch in a switch start circuit should be changed with each lamp change.

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Table 3.3.Examples of switching frequency and ballast influence on lamp life (50% survivor)of the TLD and T5 linear fluorescent lamps. (Note: T5 lamps use only electronicballasts.)

High frequencyelectronic ballast

Conventional(magnetic) ballast

Switchingcycle

Programmedstart (preheat)

Instant start(non-preheat)

Inductivecircuit

Lead lag circuit(50% capacitive,50% inductive)

12 h 23 000 h 19 000 h 18 000 h 15 000 h

8 h 22 000 h 17 000 h 16 000 h 14 000 h

3 h 20 000 h Not available 15 000 h 12 000 h

1 h 16 000 h Not available 12 000 h 9 000 h

For accurate data always consult the manufacturer.

3.4 Luminaire maintenance factor

Luminaire maintenance factor is the relative output of the luminaire due to dirt deposited onlamps and on or in the luminaires over a period. The rate of reduction depends on theconstruction of the luminaire and on the nature and density of airborne dirt present in theatmosphere. Black dirt or dust will generally cause the greatest loss of light. It is notuncommon to find 50% loss, due to dirt, from industrial lighting systems between longcleaning intervals. The amount of light loss depends on the nature and density of airbornedirt, luminaire design, luminaire material and finish and lamp type. Ventilated luminairescollect less dirt if the location of openings is arranged so that convection air currents can carrydust and dirt, pass the optic and lamp (sometimes referred to as self cleaning action) ratherthan allow it to deposit and accumulate on the reflecting or emitting surfaces. Dirtaccumulation on reflecting surfaces can be minimised by sealing the lamp compartmentagainst entry of dust and moisture. Significant benefits can be obtained with the luminairehousing and optic sealed to at least IP54 protection. Luminaire finishes differ in theirresistance to dirt accumulation. For example anodised aluminium will stay clean longer thanwhite enamel, but the former will have slightly lower initial reflectance whilst the latter can becleaned easily. Also the dirt deposit can affect the intensity distribution of the luminaire. It canturn a specular surface reflector into a matt finish or a prismatic controller into a diffuser.Table 3.4 shows typical data for a range of luminaires.

For more accurate data consult the luminaire manufacturer.

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D0,73

0,68

0,52

0,65

0,79

0,45

0,85

N0,79

0,74

0,61

0,73

0,84

0,55

0,90

C0,85

0,79

0,74

0,79

0,90

0,70

0,95

3,0

VC

0,92

0,89

0,87

0,89

0,92

0,85

0,98

D0,75

0,71

0,54

0,68

0,80

0,51

0,86

N0,82

0,76

0,64

0,75

0,85

0,60

0,91

C0,87

0,82

0,77

0,81

0,90

0,73

0,952

,5

VC

0,93

0,91

0,89

0,90

0,92

0,86

0,98

D 0,7

8

0,7

5

0,5

9

0,7

1

0,8

1

0,5

7

0,8

7

N0,84

0,80

0,69

0,77

0,86

0,66

0,92

C0,89

0,84

0,80

0,83

0,91

0,77

0,962

,0

VC

0,94

0,92

0,91

0,91

0,93

0,88

0,99

D0,80

0,79

0,66

0,73

0,83

0,65

0,89

N0,87

0,83

0,74

0,79

0,88

0,73

0,94

C 0,91

0,87

0,84

0,85

0,92

0,81

0,971

,5

VC

0,95

0,94

0,93

0,93

0,92

0,91

0,99

D0,83

0,83

0,75

0,77

0,86

0,74

0,93

N0,89

0,86

0,81

0,82

090

0,81

0,96

C0,93

0,90

0,89

0,88

0,94

0,86

0,991

,0

VC

0,96

0,95

0,94

0,94

0,96

0,93

1,00

D0,88

0,88

0,85

0,83

0,91

0,85

0,98

N0,92

0,91

0,89

0,87

0,93

0,89

0,99

C0,95

0,95

0,93

0,92

0,96

0,92

1,000

,5

VC

0,98

0,96

0,95

0,94

0,94

0,94

1,00

0

Environment

Any

1 1 1 1 1 1 1

Table3.4.Examplesofluminairem

aintenancefactors(LMF).

Ela

psedtime

between

c

leanings

inyears

L

uminaire

type

(s

eeTable

2.2)

A B C D E F G

Foraccuratedataalwaysconsultth

emanufacturer.

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3.5 Room surface maintenance factor (RSMF)

Room surface maintenance factor (RSMF) is the relative proportion of the initial inter-reflectedcomponent of illuminance from the installation after a certain period due to dirt on roomsurfaces. Tables 3.6 - 3.8 provide examples of RSMFdata. The room surface maintenancefactor can also be regarded as the ratio of the utilance of a given installation after a specifiedtime to the utilance of the same installation (without a change of the relative distribution of thedirect fluxes onto all reflecting surfaces) when new or after the last cleaning. The roomsurface maintenance factor depends on the room proportion, on the reflectance of allsurfaces and on the direct flux distribution of the installed luminaires. The room surfacemaintenance factor also depends on the nature and density of dust present or generated inthe room. This build up of dirt on the room surfaces over a period of time will reduce theavailable amount of inter-reflected light. While periodic cleaning and painting of walls andceilings is advisable in all installations it should be done more frequently in areas where alarge proportion of light arrives on the task by reflection from the room surfaces or curtains,pictures and furniture. Clean room surfaces will help the luminance balance in theenvironment. In some countries redecoration of the room surfaces is required at regularintervals set out in hygiene regulations.

Under the assumption that the decrease of the reflectance of any particular room

surface over time can be expressed by using the formula shown below (Wittig et al., 1965)the room surface maintenance factor can be evaluated for any maintenance interval. For aset of realistic values of c and the room surface maintenance factor values can becalculated for very clean, clean, normal and dirty environment conditions and the resultspresented for different reflectance conditions in tables just like utilisation factors. For practicalreasons it is sufficient to generate tables for only one medium proportion room size (k = 2,5)but for at least 3 flux distributions [Downward Flux Fraction (DFF) of 0,0, 0,5 and 1,0] formaintenance intervals of up to 6 years. Table 3.5 provides values for the constants c and and Tables 3.6, 3.7 and 3.8 give RSMFvalues for cosine distribution type luminaire havingflux fraction of 0,0 or 0,5 or 1,0 for a set of reflectance and environment. Clearly RSMFvaluescan be generated for other luminous intensity and flux distribution type luminaires.

Note: the Downward Flux Fraction (DFF) is the ratio of the Downward Light Output Ratio

(DLOR) and the Light Output Ratio (LOR) of the luminaire.DFF= DLOR/LOR

(t) = o[ c + ( 1 c ) et/]

where (t) is the reflectance at a specified time tin years;o is the initial reflectance;c, are constants of the dust accumulation process.

Table 3.5.Table of values for constants c and .

Environment Ceiling cc

Walls cw

Floor cf

(applied to

time in years)

Very clean 0,96 0,92 0,85 6/12

Clean 0,92 0,84 0,70 5/12

Normal 0,83 0,70 0,50 4/12

Dirty 0,70 0,45 0,30 3/12

Note: Maintenance data is usually provided in tabular form. However, it is often convenient topresent the data in graphical forms.

Some examples for fluorescent lamps/luminaires and room surface are shown inFigure 3.3.

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Table 3.6. Table of Room Surface Maintenance Factor (RSMF) for direct flux distribution(DFF= 0,0).

0,00 0,50 1,00 1,50 2,00 2,50 3,00 3,50 4,00 4,50 5,00 5,50 6,00Reflectances

ceiling/walls/floor

time/yrs

environment room surface maintenance factors utilisation plane

very clean 1,00 0,97 0,96 0,95 0,95 0,95 0,95 0,95 0,95 0,95 0,95 0,95 0,95

clean 1,00 0,93 0,92 0,91 0,91 0,91 0,91 0,91 0,91 0,91 0,91 0,91 0,91

normal 1,00 0,88 0,86 0,86 0,85 0,85 0,85 0,85 0,85 0,85 0,85 0,85 0,850,80/0,70/0,20

dirty 1,00 0,81 0,80 0,80 0,80 0,80 0,80 0,80 0,80 0,80 0,80 0,80 0,80

very clean 1,00 0,98 0,97 0,97 0,97 0,97 0,97 0,97 0,97 0,97 0,97 0,97 0,97

clean 1,00 0,95 0,94 0,94 0,94 0,94 0,94 0,94 0,94 0,94 0,94 0,94 0,94

normal 1,00 0,91 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,900,80/0,50/0,20

dirty 1,00 0,86 0,85 0,85 0,85 0,85 0,85 0,85 0,85 0,85 0,85 0,85 0,85

very clean 1,00 0,99 0,98 0,98 0,98 0,98 0,98 0,98 0,98 0,98 0,98 0,98 0,98

clean 1,00 0,97 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96

normal 1,00 0,94 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,930,80/0,30/0,20

dirty 1,00 0,91 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,90

very clean 1,00 0,97 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96

clean 1,00 0,94 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,92

normal 1,00 0,89 0,87 0,87 0,87 0,87 0,87 0,87 0,87 0,87 0,87 0,87 0,870,70/0,70/0,20

dirty 1,00 0,83 0,81 0,81 0,81 0,81 0,81 0,81 0,81 0,81 0,81 0,81 0,81

very clean 1,00 0,98 0,97 0,97 0,97 0,97 0,97 0,97 0,97 0,97 0,97 0,97 0,97

clean 1,00 0,96 0,95 0,94 0,94 0,94 0,94 0,94 0,94 0,94 0,94 0,94 0,94

normal 1,00 0,92 0,91 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,900,70/0,50/0,20

dirty 1,00 0,87 0,86 0,86 0,86 0,86 0,86 0,86 0,86 0,86 0,86 0,86 0,86

very clean 1,00 0,99 0,98 0,98 0,98 0,98 0,98 0,98 0,98 0,98 0,98 0,98 0,98

clean 1,00 0,97 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96

normal 1,00 0,95 0,94 0,94 0,94 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,930,70/0,30/0,20

dirty 1,00 0,92 0,91 0,91 0,91 0,91 0,91 0,91 0,91 0,91 0,91 0,91 0,91

very clean 1,00 0,98 0,97 0,97 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96

clean 1,00 0,95 0,94 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,93

normal 1,00 0,91 0,89 0,89 0,89 0,89 0,89 0,89 0,89 0,89 0,89 0,89 0,890,50/0,70/0,20

dirty 1,00 0,85 0,84 0,84 0,84 0,84 0,84 0,84 0,84 0,84 0,84 0,84 0,84very clean 1,00 0,98 0,98 0,98 0,98 0,97 0,97 0,97 0,97 0,97 0,97 0,97 0,97

clean 1,00 0,97 0,96 0,95 0,95 0,95 0,95 0,95 0,95 0,95 0,95 0,95 0,95

normal 1,00 0,94 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,920,50/0,50/0,20

dirty 1,00 0,89 0,89 0,88 0,88 0,88 0,88 0,88 0,88 0,88 0,88 0,88 0,88

very clean 1,00 0,99 0,99 0,98 0,98 0,98 0,98 0,98 0,98 0,98 0,98 0,98 0,98

clean 1,00 0,98 0,97 0,97 0,97 0,97 0,97 0,97 0,97 0,97 0,97 0,97 0,97

normal 1,00 0,96 0,95 0,95 0,95 0,95 0,95 0,95 0,95 0,95 0,95 0,95 0,950,50/0,30/0,20

dirty 1,00 0,93 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,92

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Table 3.7.Table of Room Surface Maintenance Factor (RSMF) for direct/indirect fluxdistribution (DFF= 0,5).

0,00 0,50 1,00 1,50 2,00 2,50 3,00 3,50 4,00 4,50 5,00 5,50 6,00Reflectances

ceiling/walls/floor

time/yrs


very clean 1,00 0,95 0,94 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,93

clean 1,00 0,90 0,88 0,87 0,87 0,87 0,87 0,87 0,87 0,87 0,87 0,87 0,87

normal 1,00 0,81 0,78 0,77 0,77 0,77 0,77 0,77 0,77 0,77 0,77 0,77 0,770,80/0,70/0,20

dir ty 1,00 0,70 0,67 0,67 0,67 0,67 0,67 0,67 0,67 0,67 0,67 0,67 0,67

very clean 1,00 0,96 0,95 0,95 0,95 0,95 0,95 0,95 0,95 0,95 0,95 0,95 0,95

clean 1,00 0,93 0,91 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,90

normal 1,00 0,85 0,83 0,82 0,82 0,82 0,82 0,82 0,82 0,82 0,82 0,82 0,820,80/0,50/0,20

dir ty 1,00 0,76 0,73 0,73 0,73 0,73 0,73 0,73 0,73 0,73 0,73 0,73 0,73

very clean 1,00 0,97 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96

clean 1,00 0,94 0,93 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,92

normal 1,00 0,89 0,87 0,86 0,86 0,86 0,86 0,86 0,86 0,86 0,86 0,86 0,860,80/0,30/0,20

dir ty 1,00 0,81 0,79 0,78 0,78 0,78 0,78 0,78 0,78 0,78 0,78 0,78 0,78

very clean 1,00 0,96 0,94 0,94 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,93

clean 1,00 0,91 0,89 0,88 0,88 0,88 0,88 0,88 0,88 0,88 0,88 0,88 0,88

normal 1,00 0,83 0,80 0,79 0,79 0,79 0,79 0,79 0,79 0,79 0,79 0,79 0,790,70/0,70/0,20

dir ty 1,00 0,72 0,69 0,69 0,69 0,69 0,69 0,69 0,69 0,69 0,69 0,69 0,69

very clean 1,00 0,97 0,96 0,95 0,95 0,95 0,95 0,95 0,95 0,95 0,95 0,95 0,95

clean 1,00 0,93 0,91 0,91 0,91 0,91 0,91 0,91 0,91 0,91 0,91 0,91 0,91

normal 1,00 0,87 0,84 0,84 0,83 0,83 0,83 0,83 0,83 0,83 0,83 0,83 0,830,70/0,50/0,20

dir ty 1,00 0,77 0,75 0,75 0,75 0,75 0,75 0,75 0,75 0,75 0,75 0,75 0,75

very clean 1,00 0,98 0,97 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96

clean 1,00 0,95 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,93

normal 1,00 0,90 0,88 0,87 0,87 0,87 0,87 0,87 0,87 0,87 0,87 0,87 0,870,70/0,30/0,20

dir ty 1,00 0,82 0,80 0,80 0,80 0,80 0,80 0,80 0,80 0,80 0,80 0,80 0,80

very clean 1,00 0,97 0,95 0,95 0,95 0,95 0,95 0,95 0,95 0,95 0,95 0,95 0,95

clean 1,00 0,93 0,91 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,90

normal 1,00 0,86 0,83 0,83 0,83 0,83 0,83 0,83 0,83 0,83 0,83 0,83 0,830,50/0,70/0,20

dir ty 1,00 0,76 0,74 0,74 0,74 0,74 0,74 0,74 0,74 0,74 0,74 0,74 0,74very clean 1,00 0,97 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96 0,96

clean 1,00 0,94 0,93 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,92

normal 1,00 0,89 0,87 0,86 0,86 0,86 0,86 0,86 0,86 0,86 0,86 0,86 0,860,50/0,50/0,20

dir ty 1,00 0,81 0,79 0,79 0,79 0,79 0,79 0,79 0,79 0,79 0,79 0,79 0,79

very clean 1,00 0,98 0,97 0,97 0,97 0,97 0,97 0,97 0,97 0,97 0,97 0,97 0,97

clean 1,00 0,96 0,95 0,94 0,94 0,94 0,94 0,94 0,94 0,94 0,94 0,94 0,94

normal 1,00 0,92 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,900,50/0,30/0,20

dir ty 1,00 0,85 0,84 0,84 0,84 0,84 0,84 0,84 0,84 0,84 0,84 0,84 0,84

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Table 3.8.Table of Room Surface Maintenance Factor (RSMF) for indirect flux distribution(DFF) = 1,0).

0,00 0,50 1,00 1,50 2,00 2,50 3,00 3,50 4,00 4,50 5,00 5,50 6,00Reflectances

ceiling/walls/floor

time/yrs


very clean 1,00 0,93 0,91 0,90 0,90 0,90 0,90 0,89 0,89 0,89 0,89 0,89 0,89

clean 1,00 0,86 0,82 0,81 0,81 0,81 0,81 0,81 0,81 0,81 0,81 0,81 0,81

normal 1,00 0,72 0,67 0,66 0,66 0,66 0,66 0,66 0,66 0,66 0,66 0,66 0,660,80/0,70/0,20

dirty 1,00 0,54 0,50 0,49 0,49 0,49 0,49 0,49 0,49 0,49 0,49 0,49 0,49

very clean 1,00 0,94 0,93 0,92 0,92 0,92 0,91 0,91 0,91 0,91 0,91 0,91 0,91

clean 1,00 0,88 0,85 0,84 0,84 0,84 0,84 0,84 0,84 0,84 0,84 0,84 0,84

normal 1,00 0,76 0,72 0,71 0,71 0,71 0,71 0,71 0,71 0,71 0,71 0,71 0,710,80/0,50/0,20

dirty 1,00 0,59 0,55 0,55 0,55 0,55 0,55 0,55 0,55 0,55 0,55 0,55 0,55

very clean 1,00 0,96 0,94 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,93

clean 1,00 0,90 0,88 0,87 0,87 0,87 0,87 0,87 0,87 0,87 0,87 0,87 0,87

normal 1,00 0,80 0,76 0,75 0,75 0,75 0,75 0,75 0,75 0,75 0,75 0,75 0,750,80/0,30/0,20

dirty 1,00 0,64 0,60 0,60 0,60 0,60 0,60 0,60 0,60 0,60 0,60 0,60 0,60

very clean 1,00 0,93 0,91 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,90 0,90

clean 1,00 0,86 0,83 0,82 0,81 0,81 0,81 0,81 0,81 0,81 0,81 0,81 0,81

normal 1,00 0,73 0,68 0,67 0,67 0,67 0,67 0,67 0,67 0,67 0,67 0,67 0,670,70/0,70/0,20

dirty 1,00 0,55 0,51 0,50 0,50 0,50 0,50 0,50 0,50 0,50 0,50 0,50 0,50

very clean 1,00 0,95 0,93 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,92

clean 1,00 0,89 0,86 0,85 0,85 0,84 0,84 0,84 0,84 0,84 0,84 0,84 0,84

normal 1,00 0,77 0,73 0,72 0,72 0,72 0,72 0,72 0,72 0,72 0,72 0,72 0,720,70/0,50/0,20

dirty 1,00 0,60 0,56 0,55 0,55 0,55 0,55 0,55 0,55 0,55 0,55 0,55 0,55

very clean 1,00 0,96 0,94 0,94 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,93 0,93

clean 1,00 0,91 0,88 0,87 0,87 0,87 0,87 0,87 0,87 0,87 0,87 0,87 0,87

normal 1,00 0,80 0,77 0,76 0,76 0,76 0,76 0,76 0,75 0,75 0,75 0,75 0,750,70/0,30/0,20

dirty 1,00 0,65 0,61 0,60 0,60 0,60 0,60 0,60 0,60 0,60 0,60 0,60 0,60

very clean 1,00 0,94 0,92 0,91 0,91 0,91 0,91 0,91 0,91 0,91 0,91 0,91 0,91

clean 1,00 0,87 0,84 0,83 0,83 0,83 0,83 0,83 0,83 0,83 0,83 0,83 0,83

normal 1,00 0,75 0,70 0,69 0,69 0,69 0,69 0,69 0,69 0,69 0,69 0,69 0,690,50/0,70/0,20

dirty 1,00 0,57 0,52 0,52 0,52 0,52 0,52 0,52 0,52 0,52 0,52 0,52 0,52very clean 1,00 0,95 0,93 0,93 0,93 0,92 0,92 0,92 0,92 0,92 0,92 0,92 0,92

clean 1,00 0,90 0,87 0,86 0,86 0,85 0,85 0,85 0,85 0,85 0,85 0,85 0,85

normal 1,00 0,78 0,74 0,73 0,73 0,73 0,73 0,73 0,73 0,73 0,73 0,73 0,730,50/0,50/0,20

dirty 1,00 0,61 0,57 0,57 0,57 0,57 0,57 0,57 0,57 0,57 0,57 0,57 0,57

very clean 1,00 0,96 0,95 0,94 0,94 0,94 0,94 0,94 0,94 0,94 0,94 0,94 0,94

clean 1,00 0,91 0,89 0,88 0,88 0,88 0,88 0,88 0,88 0,88 0,88 0,88 0,88

normal 1,00 0,81 0,78 0,77 0,77 0,77 0,77 0,77 0,77 0,77 0,77 0,77 0,770,50/0,30/0,20

dirty 1,00 0,66 0,62 0,61 0,61 0,61 0,61 0,61 0,61 0,61 0,61 0,61 0,61

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Lamp lumen maintenance of fluorescent lamps

0.2

0.4

0.6

0.8

1.0

Tri-phosphor

2 4 12 14 166 8 10

Halophosphate

Hours of use (kHours)

LLMF

L

LMF

1,0

0,8

0,6

0,4

0,2

Triphosphor

Halophosphate

2 4 6 8 10 12 14 16

Hours of use (khours)

Survival of fluorescent lamps

High frequencyMagnetic

2 4 12 14 16

H

18 26 8 10

0

ours of use (kHours)

0

0.2

0.4

0.6

0.8

1.

LSF

LSF

1,0

0,8

0,6

0,4

0,2

Magnetic High frequency

2 4 6 8 10 12 14 16 18 20

Hours of use (khours)

Luminaire maintenance, Type C

LMF

Years of use

Clean

1.0

0.8

0.6

0.4

0.2

321

Very clean

Normal

Dirty

1,0

0,8

0,6

0,4

0,2

Very clean

Clean

Normal

DirtyLMF

1 2 3

Years of use

Room surface maintenance, clean environment

50:30:20

80:70:20

1 2 3

0.2

0.4

0.6

0.8

1.0

Years of use

RSMF

1,0

0,8

0,6

0,4

0,2

50/30/2080/70/20

RSMF

1 2 3

Years of use

Fig. 3.3.Examples of recoverable maintenance factor data.

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D 0,59

0,59

0,60

0,62

0,70

0,38

0,75

N 0,69

0,67

0,69

0,69

0,76

0,55

0,81

C 0,80

0,77

0,79

0,78

0,83

0,68

0,87

Highpressuresodium

(250/40

0W)

VC

0,86

0,85

0,86

0,86

0,88

0,80

0,91

D 0,54

0,54

0,56

0,58

0,64

0,35

0,70

N 0,64

0,62

0,63

0,64

0,70

0,51

0,75

C 0,74

0,71

0,73

0,72

0,77

0,63

0,81

Metalhalide

(250/400W)

VC

0,79

0,79

0,79

0,79

0,81

0,74

0,84

D 0,56

0,56

0,58

0,60

0,67

0,37

0,72

N 0,66

0,64

0,66

0,66

0,73

0,52

0,78

C 0,76

0,74

0,75

0,74

0,80

0,65

0,84

HFwithpre-heat

fluorescent

lineartri-phosphor

VC

0,82

0,81

0,82

0,82

0,84

0,77

0,87

D 0,55

0,55

0,57

0,59

0,66

0,36

0,71

N 0,66

0,64

0,65

0,65

0,72

0,52

0,77

C 0,75

0,73

0,74

0,74

0,79

0,64

0,83

Compactfluorescent

VC

0,81

0,80

0,81

0,81

0,83

0,76

0,86

D 0,59

0,59

0,61

0,63

0,70

0,39

0,76

N 0,70

0,73

0,69

0,70

0,77

0,55

0,82

C 0,80

0,78

0,79

0,79

0,84

0,69

0,88

Incandescenthalogen

VC

0,87

0,86

0,87

0,87

0,88

0,81

0,92

DFF

0,5

0,5

0,0

0,0

0,0

1,0

0,0

Table4.1.TypicalsetofMFvaluesforamediumsizedroomand

thevariouslampandluminairetypecombinations.

Lamptype

Environment

Luminaire

Type

A B C D E F GThistableisbasedonthefollow

ingassumptions:

mediumsizedroom(k2,5)w

ithreflectance70/50/20forceiling

,wallsandfloorrespectively;

cleaningintervalsoflampsandluminaires1year;

cleaningintervalsofroomsurfaces6years;

failedlampsarespotreplace

d;

bulkre-lampingintervals(burninghours)incandescenthalogen2000hours

(LLMF0,95);

compactfluorescent

6000hours

(LLMF0,89);

HFfluorescentlinea

r15000hours

(LLMF0,90);

metalhalide

4000hours

(LLMF0,87);

highpressuresodium20000hours

(LLMF0,94).

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4. MAINTENANCE FACTOR

Maintenance factor is defined as the ratio of illuminance produced by the lighting system aftera certain period to the illuminance produced by the system when new.

Maintenance factorin

m

E

EMF = (4.1)

where Em= maintained illuminance;Ein= initial illuminance.

By calculating the maintenance factor for different times and taking into account theproposed maintenance schedule, it is possible to predict the pattern of illuminance in aninstallation over a period of time.

The maintenance factor is a multiple of factors.

Maintenance factor MF= LLMF LSF LMF RSMF (4.2)

where LLMF is the lamp lumen maintenance factor;LSF is the lamp survival factor (used only for group replacement programmes);LMF is the luminaire maintenance factor;RSMF is the room surface maintenance factor.

4.1 Determination of maintenance factor

The magnitude of each of these factors varies with lamp, luminaire, environment, interior andtime.

For accurate assessment the manufacturers data should be used. However, sometypical data are shown in Tables 3.2 and 3.4.

The maintenance factor can be determined by the following step-by-step procedure.

Step 1. Select lamp and luminaire for the interior application (see Table 2.2).

Step 2. Determine group replacement interval of lamps (if practical).

Step 3. Obtain LLMFand LSFfrom Table 3.2 for period established in Step 2.If spot lamp replacement procedure is followed then LSFwill be 1.

Step 4. Assess the cleanliness category of the interior (see Table 2.1).

Step 5. Determine cleaning interval of luminaires and room surfaces.

Step 6. Obtain LMF from Table 3.4 for period established in Step 5.

Step 7. Obtain RSMFfrom Table 3.6 3.8 for period established in Step 5.

Step 8. Calculate MF= LLMF LSF LMF RSMF( NRF).Calculate maintenance factor to not more than two significant figures.

Note: If there are significant non-recoverable losses (NRF) than these should

be included in the final MFvalue.Step 9. It is advisable to repeat Steps 1 to 8, by adjusting the various components, so

that a range of maintenance programme options are considered at the initialdesign stage.

4.2 Use of maintenance factor (MF)

In any lighting design calculations an appropriate maintenance factor has to be included toallow for depreciation. The magnitude of the maintenance factor significantly affects thenumber of luminaires needed to produce the specified illuminance. High maintenance factorsare beneficial and can be achieved by careful choice of equipment and electing to clean theinstallation more frequently. ISO 8995/CIE S 008-2001 recommends selecting solutions sothat the maintenance factor does not fall below 0,7. Typical values are shown in Table 4.1.

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The maintenance factor can be used in the lumen method of illuminance calculation toestimate the average illuminance of the installation at a particular stage in its life. This isachieved by using the following formula:

A

MFUFNnE

=

inm (4.3)

where Em = maintained illuminance (lux);in = initial luminous flux of the light source (lumen);n = the number of lamps per luminaire;N = the number of luminaires;A = area to be illuminated (m2);UF = utilization factor for the luminaire in the room;MF = maintenance factor.

Note: This expression does not allow for the depreciation caused by non-recoverable losses.

The maintenance factor can and should be applied to all formulae used for lightingscheme calculations, e.g. luminance patterns and point-by-point illuminance plots.

It should be noted that the maintenance factor discussed here and the variation of

illuminance shown in Figure 2.1 and Figure 5.1 are from fixed power schemes. There isincreasing use of controllable electronic ballasts that allows a lighting scheme to provideconstant illuminance. In these schemes the depreciation is compensated for by increasedpower supply to the lamps and thereby increasing the light output. Experience onmaintenance of these recently introduced controllable installations is still being gathered andprecise advice cannot be offered. It is recommended that maintenance be carried out whenabout 50% of the lamps are operating at full power.

4.3 Designing out maintenance

During the design of lighting installations it is often possible to choose components, systemsand finishes that will result in the maintenance being kept to a minimum:

- choosing luminaires in which the lamp is in a dust-proof enclosure having a suitablegasket to allow the luminaire to breathe without sucking in dust;

- adopting open luminaires (self-cleaning type) where the convection currents fromthe heat produced by the lamp are directed to flow over the reflecting surfaces toprevent airborne dry dust settling;

- using air-handling luminaires where the forced ventilation assists in the removal ofdust and dirt;

- only recommending optical systems that are fit for the prevailing environmentalconditions, e.g. plastic louvres not suitable for dusty locations;

- reducing the number of variants on a scheme;

- using luminaires having few components, which, when requiring service, can be

easily handled or removed for off-site servicing;- recommending surface finishes that remain clean for long periods and are easily

cleanable;

- using reflector lamp or bare batten luminaires where the dirt is oily or "sticky".

Other ways the designer can help the maintenance and thus improve the effectivenessof maintenance are:

- planning for ease of maintenance - consider access, types of tools needed forservicing, ensuring availability of spare lamps, optics or even luminaires. Earlyliaison with maintainer to ensure understanding of requirements and procedures isalso advantageous.

- preparing a comprehensive maintenance schedule with instructions;

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- organising effective information feed back of mistakes, failures or difficulties anduse these to avoid a repetition in future projects.

4.4 Sustainability

More and more nations in the world are introducing legislations that are supportingsustainability and these rules will impact the choice of electric lighting solutions and theiroperation.

This section gives a brief insight to consideration of sustainability as applied to electriclighting systems.

An electric lighting system has a major impact on sustainability. Sustainability, as islight, is essential for the conservation of life and resource on our planet. A sustainabilityapproach will ensure that the needs of the present generation are met without loss orcompromising the ability of future generations to meet their needs. Sustainability can bepracticed through product design and by the selection and use of sustainable lightingsolutions. These techniques can also be described as eco-design or design for theenvironment.

The ideal sustainable design is designing a lighting solution that can continue forever.

This can be by products, processes or systems that can be manufactured, used and disposedindefinitely. The ideal arrangement is perpetual reuse without waste of energy, materials oremissions.

Eco-design is designing the lighting solution with the entire lifecycle in mind. Thelifecycle covers the whole life of the product or system from material acquisition, materialrefining, manufacture, installation, use, maintenance and disposal. Employing life-cycleassessment will check the environmental impact of a solution through life including all thematerials, energy and environmentally significant releases used and created during thelifecycle.

Design for environment is mainly concerned with the design for disassembly andrecycling at the end of the useful life of the lighting product or solution.

Observing these three elements of design will yield the highest sustainability of theselected, installed and operated lighting solution.

5. ECONOMICS OF SERVICING

5.1 Lamp replacement

The total lamp replacement costs comprise the cost of lamps and the cost of labour involvedincluding cost of ordering, stocking, installation, disposal, etc. The labour cost depends on thelamp change system adopted and on the inconvenience involved. The alternatives are "Spot"replacement where each failed lamp is changed or "Group" replacement where all the lamps(failed or good) are changed at some time that is less than the rated average lamp life.However, in some projects a combined spot/group lamp replacement programme is

practised. It is very important that in places where loss of a lamp may lead to dangerousworking conditions or unsafe movements the failed lamp is replaced immediately. Installationof luminaires with more than one lamp is least affected by random lamp failures.

The most economical system can be assessed as follows:

Cost of spot replacement per lamp Csis:

Cs= L+S (5.1)

where L = cost of lamp;S = cost of labour.

Cost of group replacement per lamp Cg

Cg= L+B (5.2)

where L = cost of lamp;B = cost of labour for group replacement per lamp.

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Cost of combined group and spot replacement per lamp Ct

I

CFC100C

sgt

+= (5.3)

where F = percentage of lamps failed at re-lamping interval;I = percentage of rated lamp life at group re-lamping interval.

Note: Lamps may be bulk purchased and stored for spot replacement. Also spares can bepart of initial scheme purchase.

If the good lamps (kept after group replacement) are used for subsequent spotreplacement, then FCs/I simplifies to FS/I.

The economy of group replacement heavily depends on lamp survival rate. The morelamps survive the replacement interval the fewer costly spot replacements are needed.

It is important to note that lamp replacement interval very much depends on the lampburning hours. These vary according to working hours, shifts and lighting managementoperating in the premises. Examples of annual burning hours are given in Table 3.1.

5.2 Cleaning of luminairesThe optimum interval between cleaning Tof a luminaire is reached when the cost of the lostlight output equals the cost of cleaning.

The optimum cleaning interval Tcan be determined from the expression:

years!C

2C

C

C

a

c

a

c+

=T (5.4)

where T = optimum cleaning interval;Cc= cost of cleaning the luminaire once;Ca= annual cost of owning and operating the luminaire without cleaning; = annual average rate of luminaire dirt depreciation. Values are given in Table 5.1.

Note: Cc- cost of cleaning includes the cost of any cleaning agent, special tool, platforms orequipment and the labour. The labour costs are also affected by the timing at which thecleaning is done; during normal working hours or in unsociable hours.

Ca - cost of operating includes the amortized installation cost (proportion of capitalwritten off per year), the annual energy cost (derived from energy used in kWh cost ofenergy per unit) and re-lamping cost (cost of lamps and replacement labour perannum).

Table 5.1.Typical rate of luminaire dirt depreciation the first year.

Luminaires (see Table 2.2)

Environment A B C D E F G

Very clean 0,03 0,05 0,06 0,07 0,02 0,09 0,01

Clean 0,07 0,10 0,11 0,12 0,06 0,14 0,03

Normal 0,11 0,14 0,19 0,18 0,10 0,19 0,06

Dirty 0,17 0,17 0,28 0,23 0,14 0,26 0,09

More details and options on economics of interior lighting maintenance can be found in CIE103/5 (CIE, 1993).

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5.3 Maintenance programmes

Each lighting scheme should be designed with an overall maintenance factor calculated forthe selected lighting equipment, space environment and specified maintenance programmeor schedule. The maintenance programme should include the lamp, luminaire and roomsurface cleaning intervals, the frequency of lamp replacement and the cleaning method. Themaintenance can be set for Equi or Variable interval programme. The equi intervalprogramme defines a regular pattern for cleaning and servicing (see Figure 5.1) whilst in thevariable interval maintenance programme the cleaning is carried out at uneven intervals (seeFigure 5.2). The variable interval programme is particularly advantageous where the initialand the energy cost of the lighting installation is high but the maintenance costs are low as ityields a slightly higher maintenance factor than obtained with the equi intervals method. Moredetails of the variable intervals maintenance programme can be found in the Proceedings ofthe 21st CIE Session, Venice, 1987 (DiFraia, Salemme, 1987).

20

40

60

80

100

3rdluminaireclean

1strelamp

1strooms

urfaceclean

2ndluminaireclean

1stluminaireclean

Relative maintained

illuminance

Years

1 2 3 4 5 6 7

RelativeIlluminance(%)

Relativeillluminance(%)

100

80

60

40

20

8 9 10

4thluminaireclean

5thluminaireclean

Relative maintainedillluminance

1stroomsurfaceclean

3rdilluminanceclean

1strelamp

2ndilluminanceclean

5thilluminanceclean

4thilluminanceclean

1stilluminanceclean

1 2 3 4 5 6 7 8 9 10

Years

Fig. 5.1.Equi interval maintenance programme.

100

80

60

40

20

3rdluminaireclean

1098

100

80

60

40

20

RelativeIlluminance(%)

7654321

Years

1stluminaireclean

2ndluminaireclean

5thluminaireclean

1strelamp

1strooms

urfaceclean

Relative maintained

illuminanceRelative maintainedillluminance

Relativeillluminance(%)

4thluminaireclean

6thluminaireclean

1strelamp

1stroomsurfaceclean

2ndilluminanceclean

3rdilluminanceclean

4thilluminanceclean

5thilluminanceclean

1stilluminanceclean

6thilluminanceclean

1 2 3 4 5 6 7 8 9 10

Years

Fig. 5.2.Variable interval maintenance program.

5.4 Equipment and installation

In some situations leaving failed lamps in the circuit may cause failure of other components.The replacement of these components must be judged on the potential hazard to the safeoperation of the installation. As lighting technology is constantly advancing there are manyinstances where old installations, although operating safely, will benefit from new types oflamps or optical systems or even from changing the whole installation. In these cases the

investment can be estimated against the potential savings in energy cost and service cost.Another benefit could be the improvements in the visual environment, well-being andproductivity.

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6. SERVICING LIGHTING SYSTEMS

It is important to schedule and plan in detail the access to site, type of cleaning equipmentrequired and times when servicing of the lighting installations may be made to cause leastinterruption in the workplace. However, servicing of live lighting equipment should be avoided.

6.1 Access

It is important that provision is made for access to luminaires for re-lamping and cleaning.Equipment to help in servicing is discussed in Section 8.3.

The maintainer will need to determine how to reach the luminaire, i.e. what equipmentwill be needed, platforms, ladders, bridging, etc. and what furniture will have to be moved orprotected, such as desks, machinery and display cases. It is vital to ensure that accessequipment is so located that the operators can work comfortably (avoid over reach) andsafely on the luminaires (work inside safety barriers), and have space for temporaryplacement of parts and lamps.

6.2 Cleaning luminaires

Extreme caution should be exercised when cleaning all surfaces. Some surfaces are very

susceptible to abrasion for example; polished (un-anodised) aluminium is very sensitive, asare some plastics, acrylic in particular. It is vital to consult or read the manufacturersinstructions to ensure that the correct methods are used for handling and cleaning theproducts.

The maintainer should experiment on a small test area with a method before startingthe whole job.

The maintainer should take care in handling plastic components, as with age they tendto get brittle and break easily. Depending on the environment and on the UV emission of thelight source some plastics can yellow badly. There is no successful way of cleaning this andreplacement of the part should be recommended.

Aluminium reflectors should be washed with a warm, soapy solution and rinsed

thoroughly before being air-dried. Plastic opal or prismatic lenses should be cleaned with adamp cloth (using non-ionic detergent and water) and treated with antistatic polish or sprayand allowed to dry.

Vitreous enamel, stove enamel and glass optics should be wiped with a damp clothusing a light concentration of detergent in water.

Plastic or metal louver (rectangular or square cell) optics should be dipped into a warmwater and non-ionic detergent solution and rinsed. Specular finished (particularly plastic)louvers are very difficult to clean, and their appearance deteriorates over years of use.Therefore, they should only be used where air quality is very clean, such as new officebuildings, banks, etc.

6.3 Cleaning agents

Choice of cleaning materials and methods is determined by the type of dirt to be removed andthe type of material to be cleaned. In some countries certain procedures and cleaning agentsmay not be permitted for use under environmental health regulations. It is always advisable toconsult the authorities.

The first and most commonly used is a dry chemical detergent with additives indifferent concentration levels and is used for general cleaning. It is an advantage to usecompounds that require no rinsing after the wash. For plastic materials a final treatment withantistatic substance is recommended.

The second type of cleaner is a heavy-duty liquid cleaner that may contain detergents,solvents and abrasives. It is useful for the removal of oily dirt found for example in autogarages, oily factories, etc. The cleaning agent must be tested on a sample surface to ensure

that it does not damage materials or leave deposits.

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In some very heavy oily applications the use of a high-pressure steam cleaner isrecommended for schemes that have been designed with this cleaning technique in mind.

6.4 Re-lamping

Lamps may be replaced by a variety of skilled people therefore clear instruction will beneeded on how to remove the lamps so as not to damage the lamp holders or any othercomponents of the luminaire.

When new lamps are not being put in the luminaires after the cleaning process, the oldlamps should be carefully examined and any lamp showing age should be replaced at thattime with the lamp specified by the designer. It is also advisable to replace the glow starterswitch in switch start fluorescent lamp circuits, as aged starters may stay stuck in pre-startposition and continue to draw cathode-heating current that over a short period of time candamage the ballast.

Re-lamping with new lamps should be done after the luminaire is clean and dry.Generally the replacement lamps should be only those that are recommended by thedesigner of the scheme. However, consideration should be given to the use of improvedlamps provided they are suitable for the luminaire and application and are compatible with the

circuit. Always check with the luminaire manufacturer or the scheme designer.

7. REFERENCES

CIE, 1993. CIE 103/5. The economics of interior lighting maintenance. CIE TechnicalCollection 1993, 1993.

CIE, 2001. ISO 8995/CIE S 008/E-2001.Lighting of indoor work places, 2001.

Di Fraia, L., Salemme, F., 1987. On the light loss factor of lighting systems and itsoptimisation. Proceedings of the 21st CIE Session, CIE 71-1987, 214-215, 1987.

Wittig, E., Krossawa, R., Matanovic, D., 1965. A theoretical study of the problem presented bydepreciation of the luminous flux in interior lighting installations. IES monograph Number 9,The Illuminating Engineering Society, GB, 1965.

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8. APPENDICES

8.1 Example of maintenance factor estimation

Site - factory assembling television receivers on the outskirts of a large city

Size - large open area having normal environment

Finishes - 70/30/20% reflectance of ceiling/w

Documents

CIE 97：2005