Daylight Harvesting

In a facility with skylights, windows, sidelights, you have available daylight, which varies according to the day's time. As daylight levels increase, light levels can automatically decrease to save energy. By enabling Daylight Harvesting, you can take full advantage of ambient sensitivity to manage light levels. The Target Ambient Light Level, also called Ambient Threshold, determines the light target levels. The following description explains the fields that control and configure Daylight Harvesting. 

Things to know:

• Daylight groups, which provide a uniform dim level across a group of fixtures for improved aesthetics, tend to adjust fixture light levels more slowly over minutes.
• Daylight Harvesting fixtures adjust light levels quite fast in seconds in comparison to Daylight groups. See the recommendation about how to control the pace of a Daylight Harvesting fixture changing its light level in response to Daylight.

Target Ambient Light Level

The Target Ambient Reading that the sensor attempts to achieve by adjusting its light level.

The Target Ambient Light Level is determined and set up during the initial set up of the system. This command should only be used under the direction of Enlighted field support engineers. The procedure for obtaining the best value is to perform this command when there is no ambient light (such as at night) with all the lights set to full-on. You can also set the Target Ambient Light Level for selected sensors. The value can be set manually, or the sensor’s current ambient value can be set to be the target ambient value. Contact Enlighted Customer Support to determine or set this value or refer to the Determine and Set Target Ambient Light Level article.

Ambient Reading

The ambient light level measured by the sensor.

Ambient Sensitivity

Determines a sensor’s sensitivity to light, and it ranges between 0-10.  For Daylight Harvesting to have maximum effect, it is recommended to set the ambient sensitivity to a higher value in the corresponding lighting profile. Ambient sensitivity value, which determines a sensor’s sensitivity to light, ranges between 0-10. The value 0 means that the light will not be dimmed, and value 10 means that the light is most sensitive to ambient light. Daylight Harvesting will be most effective when the value is 10.

Daylight Harvesting

Lighting Profiles can be different over different periods of the day. The Enlighted system allows for four profile periods:

• Morning,
• Day,
• Evening, and
• Night.

Each profile period has individual Min Light Level and Max. Light Level settings and Ambient Sensitivity settings (among other settings).

The values in the lighting profile specify the Min. light level when on (0-100%) that is applied to a fixture. Normally, the light is never lowered below the profile minimum. For example, if the minimum light level is set to 15% in the profile, the lights will never turn off but will be dimmed to 15% of lighting. However, when there is sufficient daylight, the lights can be turned off and not merely dimmed to the minimum value.

For daylight harvesting to be active, the option

• Enable Daylight Harvesting Override mode in the Profiles Advanced menu must be checked. By default, this will be unchecked. See Configuring Daylight Harvesting v4.6 for a step-by-step procedure.

To Turn Lights Off During Daylight Harvesting,

Selecting the Allow Daylight Harvesting to dim lights below the minimum light level overrides the Daylight harvesting mode, turning the lights off rather than merely dimming them to 15% of the min. light level specified in the lighting profile. 

Override Settings for Min. Light (Profile Minimum Override)

As the system transitions between profiles, the profile setting for minimum light is not automatically applied to maximize energy savings. The lighting profile setting, and occupancy state determine whether the light is turned on or dimmed.

For example, if the lights are off because there is no occupancy detected, then the lights will continue to be off as the system moves from the day to evening profile. This is not desirable for outdoor lights or in company lobbies because the lights should turn on irrespective of occupancy, for safety or business reasons at certain times. For example, in a parking garage or company lobby, the lights should turn on to profile minimum value even if no one is there -- for safety reasons.

In the above example, the light needs to be turned on to profile minimum value at the beginning of the profile period. For this option to be effective, enable the option At a time period change when there is no motion, allow a change in minimum light level to raise light levels as shown below.

You must also enable this option (At a time period...light levels) when the evening period is set based on the astronomical clock. See Setting Advanced Attributes when Astronomical Clock is Set.

Override Settings for Max Light (Profile Maximum Override)

By default, when daylight harvesting is active, the light level ramps to the Max light level, and decreases to the Ambient Light Level within the ramp-up time set in the profile when motion is detected.

If you would like lights to go to the Ambient Light Level instead of the Max light level when motion is detected, check the option as shown below in the Advanced Settings.

When this option is selected, the light level goes to the Target Ambient Light Level over three seconds when motion is detected. The ramp-up time in the profile is overridden and set to three seconds. If there is sufficient daylight, the lights may not turn on when motion is detected, thus increasing energy savings.

Lights Dimming Process

The dimming process can take up to 30s or a minute at an individual fixture. The Daylight fixtures adjust light levels quite fast in seconds compared to the Daylight groups, that change light levels more slowly over minutes. Generally, the lights will brighten faster than they will dim. In some cases, with motion and complete darkness, lights may brighten immediately.

Setting individual daylight harvesting (not daylight groups) requires adjusting two settings in the advanced profile setting to get a real-time reaction of dimming lights for a fixture. Select a fixture from the floor plan and double-click to view the Fixture Details window. Select the Profile tab and scroll down to view the Advanced menu. 

The two settings shown above work together and changing them too drastically can lead to discomfort for occupants. Enlighted recommends maintaining a time period of 10 seconds and 10 minutes for a consistent light level before making a change. While customers may desire a faster response, Enlighted prioritizes consistent and gradual light adjustments over rapid changes to ensure a smoother experience for users.

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To enable Daylight Harvesting for your organization, refer to the article Enabling Daylight Harvesting.