Three ways to control light in a warehouse

Almost by definition, a warehouse is a large area. If there are people working in there (it is an if - some warehouses are fully automated) then it must be illuminated to a decent level. This means the energy consumption can end up being high, unless you do something about it.

In essence, there are two types of warehouse: those with racking and those without. This will determine the lighting layout and the controls to use. Some are large open areas where goods, often on pallets, are stored no more than, say, 1.5m high. It’s a good idea when designing the lighting to install more, lower wattage luminaires with a wide light distribution. They are installed closer together to minimise shadowing and give good vertical illumination.

The other type of warehouse, which is very common, uses racking, often to a high level, maybe 6-10m.

Our warehouse uses a combination of both. On the subject of storage areas, EN 12464 says that a continuously occupied space where little perception of detail is required should be lit to 200 lx. Manned gangways/aisles should be lit to 150 lx. The vertical illuminance on the racks should also be 200 lx.

To get the greatest benefit from a control system, you must know how the warehouse is used. How long do staff stay in certain areas? Do they cluster in one spot? How much movement is there in the aisles? If you don’t ask these questions, you won’t achieve the best result.

One of the biggest savings to be made is in unoccupied aisles. I went to a distribution centre for a major wholesaler that had literally dozens of aisles. These aisles were a good 30m long, maybe more than 40m. However, at any one time, only about a quarter of the aisles were occupied.

These guys knew their controls and had installed movement detectors at the ends and along the aisles. When the aisle was empty, the luminaires dimmed to 10 per cent. As soon as someone entered, the luminaires switched to full brightness giving 200 lux both horizontally and vertically. They had further refined the technique, and achieved greater savings, by switching on only those luminaires in the vicinity of the person picking the goods. Further down the aisle, and behind, the luminaires were dimmed.

Ex-Or's QuickSet Pro setup device

Outside the aisles, savings can be made by zoning so that only the occupied areas are illuminated to full output. But beware, switching off totally can make a place look gloomy and desolate; it might even be a health and safety hazard. It’s much better to dim to 50 or 25 per cent.

If you have ever done a Leni calculation, you will know that it includes a figure for the quiescent power load of the sensors. This is also known as the parasitic load. The Ex-Or unit used here has a low rating of 150mW.

One final point that needs to be mentioned is ease of setup. With some other suppliers, commissioning can be a pain and may even require an outside specialist. Ex-Or has devoted a lot of effort developing its QuickSet Pro handheld setup controller.

Our warehouse is 25 x 50m and 14m to the apex. It is lit to 200 lux using three different types of luminaire.

This gives a general view of the whole warehouse fully lit. Like many warehouses, several types of luminaire are used. Above the tall aisles, the luminaires have a narrow oval shape that distributes the light along the aisles but minimises it in the other axis to avoid hot spots. These can be fitted with individual LightSpot HD sensors to track movement along the aisle. Alternatively, you can group the sensors. They can be controlled by Dali or DSI signals. At the ends, a mask can be fitted on the sensor so movement in the open area doesn’t trigger the aisle lights.

In the open area, mounted at the same height, are high bays with a symmetrical distribution. It’s worth noting that the Ex-Or sensor is available for different mounting heights from 2.5-16m.

Finally, there is a low level section which is used for heavy goods or which have hard-to-read labels.

 

PIR sensor showing tilting sensor

Tech spec

Control type Hi-Bay PIR for high-level luminaires plus standard mount in low area

Arrangement Individual in aisles, linked in open area

Energy saving Biggest savings are in aisles

Controls can sometimes be difficult to illustrate in a static picture. If the lights were switched off, you would see nothing. This option uses PIR controls so the luminaires only operate when people are using the aisles.

Here, the tall aisles have been switched off because no-one is using them.

The low area in the foreground is at full brightness. This is switched by the standard HD sensor. This covers an area approximately 10m in diameter. Ex-Or is proud of the optics in its products and this unit will detect large movement at the edges of the area – when someone enters the space, for example – but the central area, about 7m in diameter, will detect small movements such as staff entering data into a notepad. The HD unit contains 155 detection points, three times as many as some on the market.

The foreground open area is at 100 per cent because it is still in use, but it would be worth zoning those luminaires at the edges, especially in a larger warehouse.

 

Installed sensor seen from below

Tech spec

Control type Single PIR

Arrangement Mounted centrally

Energy saving Can be significant with intermittent use

This is the night shift. Only a few staff are working. There is no activity in the foreground and so the luminaires are dimmed to 10 per cent. This saves energy but also means there is some illumination for safety reasons and to give the staff a feeling of security. Elsewhere, the luminaires are off or at 10 per cent.

The luminaires are at 100 per cent all along the working aisle because the angle of the detector high up picks up all the movement. A useful feature of the LightSpot HD detector is that you can link a master detector to three bus sensors. Look for QuickLink in the literature. This means that data such as occupancy and light levels can be shared across the sensors.

Each detector has its own memory chip that contains particular settings such as illumination level, timing and switching frequency. These settings can be altered from ground level using the QuickSet Pro controller. This controller can also download the recorded data and then upload it to a computer or energy management software.

 

PIR sensor unit showing Dali and digital connections

Tech spec

Control type High-level PIR

Arrangement Master plus bus sensor

Energy saving The greatest savings come from switching off what isn’t needed