Lumen Maintenance Testing of Outdoor Lighting

Installations

Dr Gareth John, Technical Director, Photometric & Optical Testing

ILP Lighting Summit, 24th of September 2015

Maintenance Factor• Need for maintenance-• The luminance/illuminance initially provided by a lighting installation will

decrease gradually throughout the life of the installation. • “Ratio of the average luminance/illuminance on the working plane after a certain

period of use of a lighting installation to the average luminance/illuminance obtained under the same conditions for the installation considered conventionally as new.” CIE Technical Report 154, “Maintenance of Outdoor Lighting Systems. • Degradation is down to a combination of lamp depreciation, lamp failure and

accumulated dirt.

Maintenance FactorMF = LLMF x LSF x LMF (x SMF)*

where LLMF = the lamp lumen maintenance factor; LSF = the lamp survival factor;

LMF = the luminaire maintenance factor; and where appropriate (e.g. pedestrian subways):

SMF = the surface maintenance factor.

Lamp Lumen Maintenance Factor

Lamp Survival Factor

Luminaire Maintenance Factors

Maintenance Factor and LEDs

Measurement of Maintenance Factor

TR28- Measurement of Road Lighting Performance on site

• Based upon BS EN 13201-4, “Road Lighting, Methods of Measuring Lighting Performance• A practical guide to

onsite measurements with calibrated photometers

TR28- Measurement of Road Lighting Performance on site

• A random sample of sites are checked, ideally once a month• Multipoint measurement across a grid on the roadway• Checked against software simulation

TR28- Measurement of Road Lighting Performance on site

• Measurement conditions (from 13201-4:) • The luminaire output should be

stable• The effect of climate upon

measurement results must be considered• [Extraneous light and sources of

obstruction (parked cars, trees) must be eliminated as far as possible.

TR28- Measurement of Road Lighting Performance on site

(Obstructions)

TR28- Measurement of Road Lighting Performance on site

(Photometer)

TR28- Measurement of Road Lighting Performance on site

(Uncertainties)• Ambient temperature- 25°C or 15°C?• Moonlight- up to 0.3 lux• Cloud cover• Extraneous Light• Luminous Intensity Distribution and angular errors• Photometer- TR28 states ~6% at best

TR28- Luminous Intensity Distribution

TR28- Measurement of Road Lighting Performance on site

(Uncertainties)• What can be controlled or eliminated?• Variation in lamp type • Variation in supply voltage• Variation in lamp mounting and tilt• Accuracy of light meters

• What can’t be accurately controlled:• Access to area • Climate conditions• Obstructions• Extraneous light • Reflections from roadway

CSS Street Lighting Project 2007: Review of Maintenance

Factors• Published in 2008• Collaboration between the County Surveyors’

Society and the lighting industry• Carried out in order to assess if maintenance

factors were accurate

CSS Street Lighting Project 2007: Review of Maintenance

Factors• Sites selected at random

with at least two luminaires from each site• Testing for total lumen

output, carried out in a photometric laboratory• Luminaires tested for

light output before and after cleaning

Laboratory Testing of Luminaire Maintenance

• Uncertainties:• Environmental conditions- temperature can be controlled to within ±0.5°C and

wind speed to within ±0.2 m/s• Moonlight- not applicable• Cloud cover- not applicable• Extraneous Light- not applicable• Luminous Intensity Distribution and angular errors- not applicable because the

light distribution is integrated• Use of spectroradiometer means light measurement errors are >2%• Input voltage can be controlled to an accuracy of ±0.1 V

Laboratory Testing of Luminaire Maintenance

• Benefits-

• Elimination of unknown factors • Repeatable • Much lower level of uncertainty

Any Questions?

01242 701300