Daylight Linking/Harvesting

Daylight harvesting is a function used in light management systems that allows for automatic adjustments of lighting depending on the detected brightness of the room.

Daylight linking is very simple technology but needs careful consideration to implement well. Contrary to common belief, the light sensor does not measure the amount of light on a surface, but rather the amount of light that will be reflected off of the surface and hit the sensor. This means that the sensor will work differently when placed over a white desk than it will over a black carpet. During commissioning, you need to check if the sensor will work well or if you need to adjust the parameters.

Glamox does not promote using a daylight sensor in every luminaire. This can result in random brightness of fittings because the measured daylight on each sensor depends on the reflectance of the surface underneath it, rather than the lux level of what is underneath it. Using fewer daylight sensors allows for grouped operation and a more uniform effect.

Firstly, it’s important to decide whether you require a ‘Daylight’ or ‘Room Ambient’ orientation for the daylight sensor.

Daylight - Also known as an open loop control system or Sensor Up - has the sensor located so that it detects only daylight and is not affected by light from the luminaire(s) it controls.
In these scenarios, the sensor is either directly facing daylight or receiving only reflected natural light. It is shielded from getting any light from the luminaire(s) that it controls. The two normal ways of achieving this are:

Industrial: Facing upwards on top of a luminaire, looking upwards through a skylight in the roof.
Office: Facing out of the windows, away from the luminaire. In practice this scenario is often achieved by putting the sensor facing downward in the last tile against a window.

Room Ambient - Also known as a closed loop control system or Sensor Down - has the sensor located so that it is able to detect both the artificial luminaire light and the available daylight.

In this scenario the sensor must be aimed at a work surface that gets an equal amount of reflected natural daylight and artificial light from the luminaire(s) that it controls.

Step by step instructions

Having decided the correct method of daylight sensing for your project, the sensor must be configured during the commissioning process.

Stage 1

Place new luminaires into workspace

tap on white field under Find button - yellow icons should appear [1]
drag them to workspace

Stage 2

Tap Profiles [2]
Create a Daylight Sensor profile and rename as appropriate [3]
Tap LDR and choose Sensor Up or Sensor Down [4]
Select the Daylight Rate [5] and Save Changes [6]

DaylightRate This sets the speed of reaction to changes in daylight. If set to 60 seconds then the sensor will take 10 samples of the daylight over a 60 second period, then slowly dim the lights to the calculated level over the next 60 seconds.

Stage 3

Tap Luminaires [7] and Configure [8]
Apply the profile to the device - yellow circle should appear because of LDR [9]

Big yellow dot on the luminaire icon it means that daylight harvesting is enabled.

Stage 4

Tap Link and Daylight in the bottom left of the 'Luminaires' screen [10]
Link the Daylight Sensor to the lights to be controlled [11]

Stage 5

Replace simulated luminaries to real ones 5. Identifying luminaires (on-site)
Monitor the reading and adjust sensor if necessary [12]

Stage 6

Go to Configure [13]
Set the Target Level(s) in the Sensor [14]

Once this step is complete the daylight sensor is commissioned and Stage 7 is optional

Suggested Values

In the table below you will find the suggested values you can enter. Test them and adjust if neccessary.

Setting	Typical Value (Sensor in Daylight)	Typical Value (Sensor Shielded from Daylight)
Lamps Off Above	700	100
Lamps Min Above	600	90
Lamps Max Below	200	50

Stage 7

You may want different luminaires to respond differently to the same daylight sensor. For instance while the sensor may be instructing all of the linked lights to switch off, luminaires further away from the windows or not benefiting from an overhead skylight should not switch off but dim to a minimum level

This level is set, not in the sensor, but in the luminaire(s) and is called Min Daylight Level. The level can be set for an individual luminaire or group of luminaires by selecting a rectangular group as below

Tap on a specific luminaire(s) in Configure [15]
Tap Min Daylight Level [16]
Modify the behaviour of different target luminaries by setting their Min Daylight Level

On The Dashboard

The effect of these settings can be reviewed on the Dashboard by clicking on the Daylight Sensor and/or affected lights in the Drawings view.

Review

Click Project Info > Drawings > Select Drawing > Click on a luminaire > Click History
Each time the ACCESS POINT reports it will display the LDR value observed

Monitor

Click Project Reports > Heatmap > Select Date> Select a luminaire

This will bring up a graph which shows how the luminaire has reacted during the 24 hour period

The graph above is explained as follows:

Until Point A the luminaires will be at their maximum output.
Between A and B natural light steadily increases and the luminaires steadily dim.
At point B the luminaires are at 'Min Above Level' and will stay there until Point C.
At Point C luminaires will switch off, this is the 'Off Above Level’.

If at any stage the daylight dips below 'Off Above Level', the luminaires will stay off until it dips below the 'Min Above Level'. This prevents luminaires flicking on and off at the level (demonstrated by Point D).

At Point E luminaires remain off as they are still above the 'Off Above Level’.
At Point F luminaires remain off as this is the same scenario as Point D.
Point G as daylight level reduces, luminaires brighten until they reach their 'On Level' (maximum output) at Point H where they will remain until the cycle starts again the next day.