Luminaires

• Luminaire Characteristics
• Luminaire Classification
• Achieving Efficient Luminaires
• Suppliers

The luminaire is a significant factor in determining both the cost and performance of a public light. This section provides a basic introduction to luminaires, including the characteristics by which they can be assessed, energy use, performance and appearance of luminaires, lighting design and luminaire classifications. An understanding of this material can aid in choosing an energy efficient luminaire.

Light output performance
The light output performance determines how effectively the luminaire transfers the light output from the lamp into useful roadway lighting.

Light output is defined by three factors:

1. The efficiency of the luminaire in directing the light from the lamp onto the road
2. The amount of light trapped in the luminaire housing
3. The amount of light which comes out of the lamp up above a horizontal plane.

These are precise characteristics that can be defined respectively by a photometric plot showing the distribution of light coming out of the luminaire, the light output ratio (the percentage of useful light coming out from the luminaire) and the upwards light ratio (the percentage of light coming out of the luminaire above a horizontal plane).

Photometric plots are generated with specialised testing equipment. Data from photometric plots can be used to generate an isolux chart and determine the level of illuminance on a road way a given distance from a luminaire mounted at a specified height and angle.

This information can then be used to determine the spacings between light poles to meet the illuminance levels of the lighting standard applicable to that road. A luminaire with a high upward light ratio is both wasting light and contributing to bright night skies.

Appearance
Appearance is what the lamp looks like. The appearance of the pole can also influence how the luminaire’s appearance is perceived.

Glare
Glare is simply defined as the degree of contrast. A low, very strong source of light pointing at you has high glare. Glare is reduced with increased mounting height, increased diffuser surface area, and opaque lamps.

Ingress Protection (IP) rating
The Ingress Protection (IP) rating is a two-digit number measuring the ability of an enclosure to prevent the intrusion of dust and water.

The first digit refers to dust ingress protection, the second to water ingress protection.

Most luminaires have two enclosed areas, the lamp area, and the terminal block area. The ballast and control gear is often situated in the terminal block area. The lamp enclosure always has a higher IP rating than the terminal block enclosure. The higher the digit the higher protection.

The ability of its diffuser to self clean
This is particularly important for luminaires installed on Category V roads with high levels of traffic that may throw up water from a wet road. Dirt will tend to stick to flat, aeroscreen or cut off diffusers.
Aeroscreen luminaires do not effectively self clean.

A degree of self-washing occurs with bowl shaped diffusers from water running down the edges of the diffuser. Dirty diffusers reduce the amount of light coming out of a luminaire and reduce illumination levels.

Cost
Cost of the luminaire is most important at the time of installation, but also of relevance if the luminaire is vandalised and needs replacing.

Electrical safety
Electrical safety is an obvious requirement. Distribution companies test all luminaires for electrical safety as part of their approval process.

How easy the luminaire is to work with
The ease of working on a luminaire covers the ease with which lamps and photocells can be changed and the ease with which the luminaire itself can be installed or changed. Distribution companies strongly prefer luminaires which are easy to work on.

Ruggedness
The ruggedness of a luminaire is its ability to deal with heat, cold, vibration (which can be significant, both from traffic and winds) and rough linesmen.

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Note: the way that distribution businesses classify luminaires may vary across different states and territories. The following explanation is based on the Victorian model, in which luminaires are classified as standard or non standard.

At present, distribution businesses decide whether a luminaire is classified as standard or non-standard; in the past, however, the Victorian Electricity Supply Industry (VESI), an industry association formed by the distribution companies, has also played a role the the decision.

When a council or developer requests the use of a non-standard luminaire, the distributor will assess the luminaire’s compliance with AS/NZS 3771, as well as undertaking its own internal assessment. If it decides to accept the use of the luminaire, and agrees to provide maintenance services to the luminaire, its pricing structure is likely to be different to the one for standard luminaires.

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Light output performance

Given the same lamp, pole spacing will be maximised with a luminaire that has good light output performance. The greater the distance between poles, the less energy used (because fewer lights are needed). This leads to significant financial savings because of reduced energy bills, fewer capital costs and minimisation of ongoing maintenance.

An engineered luminaire provides the most even light distribution across the road for the greatest distance. There is, however, a trade-off between the throw of a luminaire and its upward light ratio.

Aeroscreen diffusers, typically used on higher power luminaires, stop any light from going upwards but also limit the useful sideways throw of the lamp unless mounted on a very high pole. Aeroscreen luminaires tend to require closer pole spacings, which increases the energy used per linear meter of road.

Two engineered luminaires with relatively good light output performance are Sylvania’s Urban and Pierlite’s Greenstreet.

Appearance and energy use

The appearance of the luminaire and the pole have become increasingly important in recent years. As a result new developments heavily favour decorative luminaires. These luminaires are more expensive than standard luminaires, and because of their poor light output performance, have to be installed at closer pole spacings.

Thus, as well as requiring more energy, the use of these luminaires comes at increased capital and operational costs per linear meter of street, as compared with a standard luminaire.

Councils and developers should be aware that not only are most decorative luminaires more expensive to own and operate, they also use more energy and have a larger environmental footprint per linear meter of street than standard luminaires.

Recommendations

• For new developments, councils and developers should select an engineered luminaire instead of a decorative luminaire for the best possible energy efficiency. If a decorative luminaire must be installed, install one with high light output performance. Request your lighting designer to supply pole heights and spacings, and compare them with those of an engineered luminaire (the Energy Efficient Lighting Design worksheet in the Public Lighting Calculator can be used to help with this process).
• For reduced maintenance requirements select a rugged luminaire with an IP rating of 65 or higher. If the luminaire uses an electronic ballast, ensure that the ballast is also housed in an IP65 enclosure.

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Sylvania supplies a number of luminaires, including the Urban, a relatively new standard luminaire that has been used as a substitute for the B2224 in spot replacements and new developments in Victoria. It also stocks the Suburban, a slightly smaller version of the Sylvania Urban, which is low energy.

Pierlite supplies the Greenstreet engineered luminaire.

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