This table describes the 4 basic sensor control options and their applications:
| Occupancy (switch optional but if used must be latched) |
Absence (always requires a retractive switch type) |
||||
|---|---|---|---|---|---|
| Stand alone | With override switch | As standard | Presence enabled* | ||
| Basic operation: | |||||
| Turns on the light when presence is detected | ALWAYS | YES – but only if switch is not in override off position | NEVER | YES – but only if the sensor has timed out | Turns off the light when absence is detected | ALWAYS | ALWAYS** | ALWAYS | ALWAYS |
| Suitable for working with: | |||||
| Daylight Dependency | YES | YES | Not Recommended | Not Recommended | |
| Daylight Linking | YES | YES | YES | YES | |
| Manual Dimming (at the switch) |
NO | NO | YES | YES | |
| Potential to save energy: | For comparison only | *** | **** | ***** | **** |
| Areas with no natural light, or where it is vital the lights are always on whenever an area is occupied. Ideal for circulation areas, WCs, cupboards etc. | Ability to override the lights off provides greater control and improved energy savings however we recommend first considering absence control as a possibly better alternative. | Optimal energy saving and end user control – ideal for offices, classrooms, meeting rooms, hotel rooms, storeroom, cupboards etc. | All the features of absence, but by allowing the lights to turn on with presence (after time-out) means for instance that on a dark winter’s morning the lights would switch on automatically upon entry. | ||
Use of daylight linking or daylight dependent switching
Used correctly, daylight linking or daylight dependent switching saves energy, and enhances the working environment, however the contribution from daylight must be consistent across the controlled area. If some parts of the controlled area receive much less daylight than others, occupants of the darker area may not receive sufficient light.
We strongly recommend that only the row of lights nearest the window is controlled by any daylight dependent switching sensor, and that no more than two rows of lights are controlled by one daylight-linked dimming sensor.