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Roll over each of the points on the outside of the spidergraph for an explanation below.
The European legislation calls for a Lighting Energy Numeric Indicator. This measure is a better indicator than lumens/watt or luminaire lumens/circuit watt as it takes account of lighting controls, parasitic energy used and the hours of use of a space. As a more realistic measure of the "as used" efficiency of the lighting system within a room it will become even more important in coming years. The target for a Class 1 Teaching space using daylight and presence controls is currently 24.8 kWh/m2/year (2009), so a performance lower than this is considered good.
As always the key measure of illuminance is for the horizontal of desk based task. For adult education this should be nearer 500lux, but for children and teenagers a level nearer 300lux is most appropriate.
The radar graphs show the six key measures of a lighting installation in an educational space. As these results are for a specific scheme the reader should note carefully the application layout and results and how they might apply to specific projects.
We have known for years that the tasks in any room, and particularly for teaching spaces is often not purely horizontally or desk based. The majority of teaching is bay face to face interaction and hence a measure is needed that reflects this, Though harder to measure Cylindrical Illuminance gives and excellent indicator of how well the teacher or pupils face will be lit at a point in the room. A good cylindrical illuminance is considered to be in the region of 100 to 200lux at 1.2m above the floor, but you might also consider the levels at the head height of a sitting student and standing teacher.
Direction of light as well as quantity define how well lit an object is. When that object is a face we relate the horizontal illuminance to the cylindrical illuminance at that point and refer to this ratio as the modelling index or modelling ratio. A good figure for teaching spaces is 0.3 for 500lux rooms up to about 0.5 for 300lux rooms.
Wall to Task Ratio
The ratio between wall illuminance and task illuminance is important in providing a well balanced lighting distribution within the space. Insufficient light on the walls can lead to poor definition of the extent of a room and as the walls for the majority of the view in most applications they also contribute greatly to how dim a room appears. A figure of 0.5 to 0.6 is considered good, with a result of up to 0.8 acceptable in classrooms.
Ceiling to Task Ratio
The ratio between ceiling illuminance and task illuminance is important in providing a well balanced lighting distribution within the space. Insufficient light on the ceiling can lead to the cave effect, the feeling of the ceiling being lower than it is. A figure of 0.3 to 0.9 is considered good.
Body: steel, white (close to RAL
Body: extruded aluminium, powder coated titan grey End caps: die-cast zinc Louvre:
anodised aluminium Satinbrite.
Fixed output versions delivered with 2.6m, 3 x 0.75mm2 Ø zero halogen cable. Dimmable version (DSI) delivered with 5 x 0.75mm2 non halogen cable. Mount the Quick-lock wire suspension kit (included) on to the adjustable brackets. Continuous system mounting permissible without accessories. 90 - 270° circular junction box enables flexible mounting. End caps with extensions are required for use with the junction box. Do not attach suspension wires to the junction box. It is possible to through wire from fitting to fitting or through junction boxes.
To specify state: Suspended aluminium luminaire for 28-49W T16 (T5) lamps with metal end caps and wide uplight. As Thorn Optus IV.
More information on this product can be found in the Thorn E-Catalogue.