Too little light in the warehouse: diagnosis and solution

Measure first, replace later

A complaint such as 'the warehouse is dark' is not a diagnosis. Before you order luminaires, you want to know how much light actually reaches the floor and the shelves. You measure that with a lux meter: hold the sensor horizontally at working-plane height (the floor, or 0.85 metres at packing benches), measure on a grid of roughly 2 by 2 metres and note the average and the lowest value per aisle. Exclude daylight by measuring in the evening or covering the rooflights, and let conventional lamps warm up for a quarter of an hour first.

Compare the result with the standard for workplace lighting, EN 12464-1. Broadly, its guide values are: storage areas 100 lux, gangways with traffic 150 lux, and order-picking, packing and dispatch zones 300 lux. Uniformity (lowest value divided by the average) should generally be at least 0.4. If you are well below these figures, the cause is almost always one of the four below.

Cause 1: ageing of the light source

Every light source gives less light over time while drawing the same power. Metal halide and high-pressure sodium lamps are the worst: depending on type and operating hours, they can lose 30 to 50% of their luminous flux before they fail. Fluorescent tubes typically lose 10 to 20%. A hall that was properly designed for 150 lux ten years ago may now sit at 80 to 100 lux, even though every lamp is still burning.

LED ages too, but far more slowly and predictably: a good high bay is specified at, for example, L80 at 50,000 operating hours, meaning 80% of its light is still there after that period. Cheap luminaires from the first LED generation often do not achieve this and discolour or flicker sooner. The tell-tale sign: all luminaires are on, but the hall looks dull, with visible colour differences between individual luminaires. The answer is group replacement, not lamp by lamp.

Cause 2: dirt

Dust from packaging, soot from fork-lift trucks and moisture settle on the light-emitting surface of the luminaire. At 8 to 12 metres it rarely gets cleaned. In an ordinary warehouse a dirty luminaire can quickly cost 10 to 30% of its light; with open reflectors and in dusty environments it is more. On top of that, dark racking, grimy walls and stacked pallets reflect hardly any light back.

A simple test: clean one luminaire, measure underneath it again and compare with an uncleaned neighbour. If the difference is large, cleaning belongs in the maintenance schedule. When choosing new luminaires, look for a sealed housing rated at least IP65 so no dust gets behind the lens. The high bays in the ATRIA range are IP65 with a smooth surface that is easy to clean.

Cause 3: the wrong optics above the racking

This is a common mistake in halls with racking higher than 3 metres. A round UFO high bay has a beam of 90 to 120 degrees. Mounted above a rack or diagonally above an aisle, most of its light lands on the top shelves and the pallets, not in the aisle where the order picker is reading. The result is then, for example, 400 lux on the top level and 60 lux on the floor.

The problem often appears only later: the luminaires were hung in an open hall, and racking was installed or moved afterwards without anyone looking at the lighting. The solution is a linear high bay with an asymmetric 30x90 degree beam, mounted directly above the centre line of the aisle with its long axis along the aisle. That brings the light between the racks down to the bottom shelf. One example is the ATRIA linear high bay of 100 W with 16,000 lm, 160 lm/W and exactly this optic.

Cause 4: too little luminous flux for the mounting height

Light falls off with the square of the distance. A luminaire that delivers 150 lux on the floor from 6 metres gives roughly a third of that from 10 metres. After a move to a taller hall, or when an old lighting plan is reused, the luminaires are often simply too small.

A worked example. A hall of 40 by 25 metres (1,000 m²) needs an average of 150 lux. With a maintenance factor of 0.8 and a utilisation factor of 0.6 you need 150 × 1,000 / (0.8 × 0.6) = roughly 312,000 lumens. That is about 21 UFO high bays of 100 W with 15,000 lm, or 18 of the 180 lm/W version with 18,000 lm. For halls up to 6 metres an ATRIA linear low bay with adjustable output from 14 to 75 W is often enough; for 10 to 14 metres you move up to 200 to 240 W.

How to tackle it

• Measure first: average and minimum per zone, compared with the guide values.
• Identify the cause: cleaning test, age of the lamps, beam angle relative to the racking.
• Have a lighting calculation made on the current rack layout, height and reflectances. We produce one for 350 euros excluding VAT.
• Choose the right type per zone: UFO for open floors, linear above racking, flat with UGR<21 at packing benches and workstations.
• Consider a plug-in sensor: in aisles with only occasional traffic the light dims to a base level and returns to 100% on movement.

With LED backed by a 5-year warranty and a lighting calculation up front, you know in advance which lux level to expect after installation and how it will hold up over the coming years. Lichtplein supplies businesses only, from European stock and within 5 working days.

Frequently asked questions