Retrotec USACE - Manual (Page 230)

D100 ENERGY & PROCESS ASSESSMENT PROTOCOL
visual quality gained from the use of high color temperature sources means
that you can cut the light levels and energy use in half while still maintaining
equal visual ability.
In most industrial applications, the change to fl uorescent from HPS is the
better installation, because the fi xtures can reduce glare, have instant-on capa-
bilities, and can be upgraded to two-level switching very easily. For high-bay
spaces, either fl uorescent or metal halide options are viable.
When switching to metal halide lamps, use pulse-start ceramic metal halide
lamps and electronic ballasts whenever these lamps and ballasts are available
(usually defi ned by wattages). This combination provides the best color con-
sistency (from lamp to lamp) and constancy (throughout the life of the lamp),
better CRIs, and much better lumen maintenance.
HPS should never be considered in interior applications and should essen-
tially be limited to outdoor lighting applications, particularly roadway lighting.
D.5.16 Using Poor Performance Lighting Fixtures That Trap More
Light Than They Distribute to the Task Area (Ineffi ciency)
Every lighting fi xture has an associated lighting distribution. The lighting
distribution of a fi xture is a description of the fi xture’s ability to project, or
“throw,” light in a specifi c direction. Because a lighting fi xture normally con-
tains a source, a refl ector, and often a diffuser, the challenge of fi xture design
is fi guring out how to get these components to interact together in a way that
produces the desired lighting distribution. When a fi xture design is successful,
the amount of light exiting the fi xture is close to the theoretical maximum, and
the desired lighting distribution is achieved. On the other hand, when a fi xture
design is unsuccessful, some light from the source is trapped inside and does
not exit the fi xture to light the room.
There are several measurements of fi xture effi ciency to look for. One is
fi xture effi ciency, which is the total percentage of lumens that come out of a
fi xture, compared with the raw lamp lumens. Another method is to use the
luminaire effi ciency rating (LER), which is the product of the luminaire ef-
fi ciency, rated lamp lumens, and ballast factor divided by the input watts. The
LER is therefore an overall system performance criterion. The most important
criterion, however, is the photometric distribution and its ability to perform
the task that is required. For instance, pendant-hung indirect lighting is most
effi cient when it has the widest distribution, so that most of the lumens are
being spread out across the ceiling.