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Operating Characteristics
Five operating characteristics of fluorescent lamps are:
-
EFFICACY - defines light output per
unit of power input.
-
LUMEN MAINTENANCE - defines the
decreasing light output as the lamp ages.
-
MORTALITY - defines average lamp
life expectancy.
-
COLOUR RENDERING - defines how
fluorescent lamps display the colours of objects.
-
ENVIRONMENTAL CONSIDERATIONS -
defines how fluorescent lamps respond to extremes in their operating conditions.
Fluorescent Lamp Efficacy
Lamp Efficacy =
Lumens (light output)
Watts (power consumed)
=
Lumens per Watt (L/W)
Fluorescent lamp efficacy is 3-7 times higher than incandescent:
-
100W gls 13.5 L/W
-
1500mm 58W 47-93 L/W
Fluorescent lamp efficacy is
dependent upon the lamp colour, lamp length, ambient temperature, and frequency of the supply
voltage.
Lamp efficacy varies by lamp colour:
-
Polylux XL 840 gives 93 L/W
-
Polylux Deluxe 940 gives 65
L/W
-
Cool White gives 81 L/W Polylux XL
provides the best L/W and operating efficiency.
Both lamp length and current affect
efficacy:
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Polylux XL 835
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2400mm 100W
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94 L/W
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1800mm 70W
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94 L/W
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1500mm 58W
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93 L/W
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1200mm 36W
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96 L/W
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600mm 18W
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81 L/W
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Lamp efficacy and output is affected by extremes in ambient temperature.
See Figure 5.9. Fluorescent lamps are relatively sensitive to ambient temperature
because they are low pressure lamps. Optimum lamp operating temperature is 5-25 degrees Celsius.
Above this limit the efficacy falls by approx. 1 % for every degree rise. Below this limit the
efficacy fails by approx. 5% for every degree fall. Fluorescent lamps should be protected from
draughts that can reduce lamp wall temperature and light output.
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