FEATURE LIGHTING Improving efficiency with sensors
Occupancy sensors are an effective way to control lighting and heating. However, the most efficient lighting design is when the lighting is switched off, so how do you use sensors to provide the most efficient control? B.E.G explain
F
irstly, it is important to maximise the use of natural daylight with dimming
ballasts installed in the light fittings. Once occupancy is detected the sensor measures the natural light, compares this against the pre-determined light level and turns the fitting onto the required level. Sensors are now available in the UK
which can set three different lighting bands/zones for the same area (such as for school classrooms) - i.e. one zone for the area near the windows, another for the internal area and a third for the presentation/teacher area. The lights are controlled on one occupancy control but you can have switches to provide automatic and semi- automatic function, both near the entrance and next to the presentation area, and different light levels to ensure an overall balance. The other development is controlling
the lights and heating/ventilation with one sensor so reducing wasted light but also only having the extractor fans on in a washroom when occupied. The run-on times can be set individually and you can also reduce the fan costs with the timer controlled models.
ENHANCED CONTROL For the more sophisticated building management systems you can use sensors which have built-in thermostats, such as the new Luxomat from Bruck Electronic (B.E.G.) This detects the three most important
values of a room - temperature, light level on the ceiling which transmits the measured values to two 0-10V interfaces and, thirdly, the sensor detects movement and reports this via a switch contact. This information can then be used for closed (proprietary) BUS systems (e.g. LON or SPS) and DALI systems. LEDs are now seen as the Holy Grail of
efficiency, but care must be taken to ensure that this efficiency is matched with occupancy control. Sensor control will extend the lifespan but they must be able to cope with the large in-rush currents. This is why it is crucial that the sensors are fitted with reputable relays. The less detectors you have to use and the greater the amount of lights you can
32 NOVEMBER 2014 | ELECTRICAL ENGINEERING
switch, the better. However, again attention must be made to ensure that there is the correct coverage. For example, B.E.G. has developed sensors with built-in microphones that react on occupancy with the delay time reset on sound as well as movement. This means in a washroom you do not need to install a sensor over each cubicle, rather, one centrally mounted sensor will provide the correct detection. Typical occupancy sensor applications include offices, conference rooms, washrooms, entrance halls, classrooms, corridors, toilets, basements, warehouses and outside up to a range of 20m.
APPLICATION An example of how B.E.G has helped deliver high energy efficiency with occupancy sensors is from a recent building control project it carried out at a leading independent boarding school. The Royal Hospital School in Suffolk was provided with lighting occupancy sensors that have the potential to offer
Above: for the more sophisticated building management systems you can use sensors which have built-in thermostats, such as the new Luxomat from Bruck Electronic (B.E.G.)
Below: B.E.G has
helped deliver high energy efficiency to the Royal Hospital School in Suffolk
energy savings of up to 80%. After an extensive lighting site survey by B.E.G., the Royal Hospital School has replaced its conventional switches with more than 50 of the company’s Luxomat two channel occupancy sensors. Installing the Luxomat means the occupancy detector switches on light, heating and ventilation only when required. The sensor is a motion detector designed specifically for ceiling mounting and its optical system has a coverage angle of 360°. It is high resolution and well suited for a school environment where most of the activity in a classroom, for example, occurs when pupils are sitting down. In addition to movement, the presence detector also senses daylight and artificial light and controls the overall brightness. If this is higher than the required luminous intensity, the artificial lighting is turned off again even though movement is present. It is switched on if not enough daylight is available. The artificial light can also be re-
adjusted to the amount that is needed to meet the pre-determined brightness level. The Royal Hospital School will also save money on maintenance costs as the Luxomat is remote controllable. The Luxomat was installed in the school’s classrooms, changing rooms, corridors and several other circulation areas. The school expects to see a return on its investment within just one year. Paul Jones, B.E.G. UK director, said, “The
school stands to make significant savings in energy consumption thanks to the installation of the Luxomat in key circulation areas of the school. The occupancy sensors will enable the Royal Hospital School to become a more energy efficient school, while allowing it to reduce its carbon footprint at the same time.”
B.E.G
www.luxomat.com T: 0870 850 5412
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