In classrooms (or conference rooms) it should be possible to switch on lighting when required (classroom has natural light from windows) and switch off lighting when the premises are empty. 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

In schoolrooms and conference rooms IR detection is combined with lens no. 51. 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. Placing the detector in the corner that is furthest from the door allows the detector to be installed higher up, which reduces the risk of tampering. When installed in this way the slightly down-tilted detection fields reach the door at the correct height. The detector fields can be tilted downwards by sliding the circuit upwards in the detector.

Information for current budget

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, see the wiring diagram below.

The lighting level is adjusted to suit the natural light (constant light level regulation) with the aid of photocell LS-10.

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. Each time the lighting is switched on the system reverts to the preset constant light level regulation.

The dynamic system uses light fittings with dimmable HF ballasts, presence detection, level selection and a photocell.

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:

• Uniformly distributed base lighting without additional light fittings that operate at 100 per cent.
• Possibility of saving 20–99 per cent in operation.
• Lower working temperature of light fittings, with consequent increase in working life.
• Less frequent switching and lower supplied output reduces wear to fluorescent coating and extends life of light sources.
• Less need to follow light source manufacturer’s recommended burn times, drastically reducing run times and increasing savings.

1. Light level when lighting is initially dimmed (lighting output is reduced)
2. Light level when lighting is set to minimum output setting
3. Light level when lighting is initially ramped up
4. Light level when lighting is set to maximum output setting (80%)
5. A cloud causes the light level to fall temporarily and so increases the lighting output temporarily