In a large area, how does light controls detect where to dim?

Hi guys, I have a question. when we have a 500 m2 office and we use the light control option for dimming, does the energyplus dims the whole area of just a part of it?

EnergyPlus uses a single sensor in the middle of the Zone to determine when to dim the zones lights. You can set the XYZ coordiates of this point for each Zone using the daylightCntrlPt_ input on the “Set EnergyPlus Zone Thresholds” component. Based on the illimunance at this point in relation to the daylightIllumSetPt_, the lights will dim down to a fraction of the total lighting load, which you can set using the daylightCntrlFract_ input on the “Set EnergyPlus Zone Thresholds” component.

If you need to model anything more sophisticated than this, then your best option is to build a detailed Daylight model with Radiance and use the results to generate your own lighting schedule for EnergyPlus.

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@chris thank you. can I hypothetically create multiple zones within a zone for lighting study only? so that the whole zone that I am looking for will have multiple sensors?

And I guess that the Auto turns on when the schedule is having occupants

You can’t really create several lighting zones within EnergyPlus thermal zones. So, if you are going down the route of something more sophisticated with Radiance, my suggestion is to split up the large space into multiple HBZones and use the Radiance results and occupancy schedule to generate a custom CSV lighting schedule for each of these subdivided zones.

Subdividing the large space into core/perimeter zones can also be a strategy that you can use with EnergyPlus’s built-in light dimming for daylight. But just be aware that the light will never cross an interior wall in EnergyPlus simulations with Honeybee Legacy, even if it’s an air wall. So make sure you have zoned it in a way that the core zone has no daylight controls.

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@chris thank you I assume this applies to honeybee+ too

Well…not quite. EnergyPlus finally added true air walls (aka. Construciton:AirBoundaries) a few months ago in E+ 9.3. While it’s too late for us to make use of them in legacy without running the risk of breaking things, these AirBoundaries have made it into the Honeybee[+] that’s under development and that we will officially release soon.

As you can see, those AirBoundaries allow you to run the simulation with “GroupedZones”, where you get both daylight and all radiant heat exchange crossing the boundary as if it didn’t exist. So you will have a more elegant means of accounting for multiple daylight sensors in E+ soon.