There is no formal calculation of reference point light levels from artificial lighting sources. Only the reference point light levels from daylighting sources are calculated and reported as Morgan mentions below. The light level from artificial sources is assumed to be the design light level adjusted by its associated schedule (if applicable) and by the lighting power reduction factor and the relationship between fractional input power vs. fractional light output defined in the Daylighting:Controls input object.
Rob Hitchcock
----- Original Message -----
From: "goff.morgan" <mgbane@xxxxxxxxx>
Date: Wednesday, January 28, 2009 9:17 am
Subject: [EnergyPlus_Support] Re: Variables to measure the Zone lux level
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Hello Andre,
>
> So, I have a building I'm working on that uses solatube's for
> extra
> lighting during the daytime. So as the solatubes collect more
> lighting from the sun, the lighting power from the existing
> lighting
> in the building will ramp down (put out less wattage).
> So here's a sample of my data. Column 1 is output variable
> "Daylight
> Illum at Ref Point" and Column 2 is "Ltg Power Multiplier from
> Daylighting". So its a decimal form of the percentage of lighting
> the building requires to satisfy your setpoints. So as the lux
> increases, lighting power from building is reduced.
> 37 lux = 5% reduction
> 385 lux = 53% reduction
>
> Column 1 [lux] Column 2 [unitless]
> 37.11481104 0.955515326
> 188.5679641 0.757688626
> 385.411255 0.469558702
> 299.9273695 0.60845007
> 186.3168134 0.764873899
> 264.0468125 0.657083824
> 323.9869944 0.652336076
> 196.7505115 0.766595286
> 111.9851288 0.853581824
> 9.795133401 0.987605888
>
> So I hope that answers your question on the "Ltg Power Multiplier
> from Daylighting" output variable. And I didn't have any luck
> finding an output variable that could tell you the lux (both
> generated by lighting and daylighting) in an area for all time.
>
> Good luck
> Morgan
>
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, André Lopes
> <andr_lopes2000@...> wrote:
> >
> > Hi all
> >
> > Can you you tell what are the correct variables to measure a
> zone lux level (during day and night).
> >
> > What is meaning of this variable: Ltg Power Multiplier from
> Daylighting
> >
> > I read the Manual, but I did not understand it.
> >
> > Regards
> >
> > A L
> >
>
>
>
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