In office rooms and other small rooms it is usually hard to justify investment in presence-controlled lighting on a purely financial basis. The investment cost of existing technology is too high in relation to the possible reduced energy consumption (saving). Detection in this type of premises uses IR detectors equipped with a high-resolution lens. To improve the results and increase the saving, wall sockets can also be connected to the presence control. This means that fittings for desk lights, point lighting, monitors etc. can be presence-controlled.

Other benefits such as environmental and convenience benefits can often be entered in a ‘calculation’, which can lead to justification of the investment. Future increased energy prices and more advanced and cheaper technology can also make it profitable to invest in presence-controlled lighting in office rooms.

In offices it must be possible to switch on lighting when needed (room has natural lighting from windows) and switch lighting off when leaving the room. When special activities take place it should be possible to dim the lighting manually to the required level. It would be an infringement of personal freedom to set a light level that cannot be changed. Different people have different lighting needs for different activities. NV-3TR provides the possibility to regulate the light level manually.
The premises have large windows and let in a large amount of natural light. A dynamic daylight-dependent lighting system is therefore installed. This allows the lighting level to adjust automatically to suit the natural light and the way that the premises are used. When presence is detected, the lighting level is increased gradually from the base lighting level of around one per cent to a level that is determined by the amount of natural light entering the room.

Light sources

The light fittings have dimmable HF ballasts with analogue control (1–10 V).

Detector placement

An IR detector with a number 51 lens is used in office space. This gives the maximum possible resolution and hence the ability to detect small movements.
The placement of the detector is critical to performance! The illustration below shows how the detector should be positioned. When combined with lens no. 51, which permits higher installation, this enables optimum detection on entry. In addition, the detector cannot see out through the door, which means that the lighting does not remain switched on when people pass by in the corridor outside.

To exploit the hidden savings potential available in all areas that have natural lighting, the installation should include an on/off logic module that prevents the lighting from being switched on when someone enters. All activities may not require artificial lighting in addition to the available natural light, so personal needs should decide when lighting is switched on. This means that the lighting is switched on and off in the usual way using a pushbutton. The detector only comes into action and dims the lighting to the base level (one per cent) after the set time (3–5 min.) when someone forgets to switch a light off. To use this function a 4.7 kohm resistor must be connected between the IR detector and the level selector.

The lighting can be adjusted to suit the natural light (daylight-dependent light) by means of the LS-10 light sensor.

The dimmable light fittings with HF ballasts are regulated by analogue control (1–10 V). The light intensity can also be adjusted manually by holding in the pushbutton.

Whenever the lighting is switched on the system reverts to the set light level for daylight-dependent lighting.

The dynamic system uses light fittings with dimmable HF ballasts, presence detection, level selection and a light sensor.
Dynamic lighting operates as follows:
When presence is detected the lighting is switched to a maximum level of 80 per cent, depending on the available natural light. One minute after presence is last detected, the lighting is reduced to 1–3 per cent. When someone enters the corridor the lighting is gradually ramped up again to a level that depends on the natural light level, as measured by the photocell (between one and 80 per cent). One hour after presence is last detected the lighting is switched off completely.
The main benefits that are obtained with dynamic lighting control are:

• Possibility of saving 20–99 per cent in operation.
• Lower working temperature of light fittings, with consequent increase in working life.
• The combination of reduced switching, reduced wear to cathodes and lower power levels that reduce wear to the fluorescent coating extends the life of light sources.
• Less need to follow light source manufacturer’s recommended burn times, drastically reducing run times and increasing savings.

Information for current budget