RETROFITTING EXEMPLARS

Pennie Varvarides discovers how Holophane retrofitted Network Rail’s light maintenance depot at Bounds Green – for the second time

When Network Rail decided to update the high bay lighting at its light maintenance depot in Bounds Green, London, Holophane was asked to supply a suitable replacement system.

The company used a combination of Prismalume luminaires and Holos 2 digital controls to replace the original high-pressure sodium scheme, and high frequency electronic ballasts will extend lamp life.

The roster of fittings includes 268 250W, 111 320W and 95 400W luminaires. Different wattages were needed because the depot comprises several buildings of differing heights.

Twenty-five-year history

Holophane is no stranger to the Bounds Green depot. Twenty-five years ago, it installed the high bay lighting scheme there.

About five years ago, that scheme was replaced with a collection of low-cost products under a design and build contract. The new fittings failed frequently and needed updating, so Network Rail called Holophane back in.

Not only was the previous installation unreliable, it was left on for 24 hours a day, a problem that Holophane has solved using Holos 2 controls.

Head of development David Barnwell says: ‘With the advent of dimming controls, we were able to offer a solution to the inevitable problem facing railway premises. To provide the specified luminance levels on walkways and platforms with rolling stock present, it is necessary to over-light the premises to cater for obstructive shadows created by the vehicles.’

Controls

The controls system measures the daylight that enters through the roof lights and modulates the artificial lighting accordingly, saving energy. The window area is 376.86m2 – 15 per cent of the ceiling – from where there is a 120-degree view of the sky.

The Prismalume high bays have prismatic glass reflectors that reflect and refract the light. They have a light output ratio of up to 95 per cent.

By tailoring the light distributions of the fittings, fewer luminaires are necessary – cutting capital and installation costs, maintenance and energy consumption while enhancing the visual environment.

Holophane’s Optimised Lighting Operating System (Holos 2) controls high-intensity discharge light sources. It dims the lighting in response to fluctuations in the amount of available daylight as rolling stock enters and leaves the depot.

In fact, changes had to be made during commissioning because the rolling stock livery changed from dark blue to bright silver.

Holos 2 changes light levels in response to signals from presence detectors, using Holophane’s dual-purpose photocell/PIR sensor.

Only about a quarter of the track is in use at any one time, and that is the only area that needs maximum light levels. The remaining 75 per cent of the track is only lit to the minimum requirement of 50per cent for security and safety.

By localising illumination, Bounds Green depot has cut energy consumption by about 38 per cent.

Barnwell says: ‘The lighting design is tailored to meet the specific needs of the project. We are very proud to be associated with such a prestigious project for a second time.’

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