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 MIL-HDBK-1013/1A
average brightest to darkest regions of the assessment zone must not exceed
three to one.
Several methods are presently used in achieving these illumination
levels. These employ high pressure sodium vapor roadway luminaires spaced to
meet both the CCTV and other security illumination requirements. The most
common variety of luminaire is the 250-watt (W) unit, while some facilities
employ a 400-W unit. Some installations have opted for 150-W luminaires with
an instant restrike capability.
4.7.5
Lighting Energy Considerations
Overview. Since the energy shortage of 1973-74, virtually every
4.7.5.1
lighting system has come under scrutiny to identify energy savings. Security
lighting systems are no exception. This scrutiny is probably as much related
to the conspicuousness of security lighting as to the amount of energy
consumed. While the only energy consumption statistics available on lighting
pertain to the energy required to maintain street lighting systems, security
lighting uses considerably less energy. Recently, the direction of the
security community to reduce energy costs in security lighting has resulted
in replacing luminaires to increase source efficacy by changing to
high-pressure sodium (HPS) lamps. HPS lamps produce more lumens per watt
than either mercury vapor or incandescent lamps. The latter two lamps are
the most widely used in the United States today. Table 9 presents the
relative efficiencies and restrike times of some typical lamps.
Table 9
Relative Efficiencies and Restrike Times of Light Sources
(From IES Lighting Handbook, J.E. Kaufman, ed.)
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*
*
*
*
Lamp Type
Efficacy
Restrike Time
*
* (Lumens/watt) *
*
(minutes)
*
*
*
*
*
Theoretical Maximum *
*
*
683
---
*
*
*
*
Ideal White Light
220
---
*
*
*
*
*
*
*
*
Incandescent
10-16
<1
*
*
*
*
Tungsten-Halogen
17-25
<1
*
*
*
*
Mercury Vapor
30-65
3-7
*
*
*
*
*
*
*
*
Fluorescent
33-77
<1
*
*
*
*
Metal Halide
75-125
up to 15
*
High-Pressure Sodium *
*
*
60-140
1 (restrike)
*
*
*
*
3-4 (warm-up to
*
*
*
*
full output)
*
*
*
*
*
Low-Pressure Sodium *
*
*
180
7-15
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90
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