# Re: [EnergyPlus_Support] Daylight

```Comments inserted below.

Rob Hitchcock
============
Fábyo Luiz Pereira wrote:

>    I´m trying to simulate a daylight example and have some doubts:
> - "Minimum input power fraction for continuous dimming control"
> (Daylighting:Detailed): This fraction is relative to the "Design Level"
> (Lights)?

RH - The assumption in EnergyPlus is that the installed electric
lighting produces exactly the design set point illuminance level at each
reference point, at 100% power.  Thus, for continuous dimming the
lighting control "curve" goes from design level at 100% power to Minimum
Light Output Fraction for Continuous Dimming Control at "Minimum input
power fraction for continuous dimming control".  So electric light
output is always treated as a percentage of the design level along this
"curve."

>
> - "Total daylighting reference points" (Daylighting:Detailed): I´m
> afraid that
> can't use 2 reference points, cause the "Daylight Illum at Ref Point"
> Report is
> giving, for some hours, nonsense values like 29000 lux. When I
> simulate the
> same building with only 1 reference point the results for this report
> seems to
> be acceptable (maximum value about 2500 lux).

RH - Note that the coordinates of Reference Points are always relative
to the Zone Coordinate System, no matter what form of geometry input you
use for everything else (e.g., Surfaces).  Make sure the relative
coordinates you have entered for your reference points do not end up
outside your building after transformation to absolute coordinates.

>
> - In my case, I´m using 3025 W of light design level per zone (each
> one have
> about 150 m2 of floor area), with visible fraction equal to 0.35. This
> way, can
> I estimate a value for my "Illuminance setpoint at first reference point"
> (Daylighting:Detailed)? I´m using the default value for this variable (500
> lux), and I know that usually we choose that based on a table, but I´m
> not sure
> that my power design level can be able to give this illuminance. For my
> viewpoint, knowing the light's visible fraction and the floor area I
> can find a
> illuminance level. Is that right?

RH - See my first comment above.  Unfortunately, it is up to you to
correctly determine that your input for electric lighting Design Level
(installed Watts) produces your desired illuminance level at daylighting
reference points.

>
>
> =====
> ________________________________________________________
> Engº Fábyo Luiz Pereira
> UFRGS - Laboratório de Vapor e Refrigeração
> Rua Sarmento Leite, 425 - Sala 203 - Centro - 90050-170
> Fone / Fax: +55 51 3316-3167 / 3316-3355
> www.mecanica.ufrgs.br/lafrig
> Porto Alegre - RS - BRASIL
>
>
>
>
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