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Figure 5.14. Colour rendering.
Fluorescent lighting is often considered a "neutral" or "cool" appearance when
compared with incandescent light. Special GE fluorescent lamps provide specific colours for plants,
aquaria,- photocopiers, and germicidal applications.
Environmental Considerations
Fluorescent lamps are affected by extremes in ambient temperature. They operate best in the
range 5-25 (35 for High Output T5) degrees Celsius. Below this there is a rapid drop in light
output and difficulty in starting.
High humidity causes electrical leakage along the lamp surface - lowers the starting voltage
provided by the ballast. Lamps are pre-coated with silicone to break up the moisture film and
prevent such leakage.
Fluorescent Lamp Advantages
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Fluorescent lamps are 3-7 times
more efficient than incandescent lamps.
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Power consumption for equal light
output is much less than for an incandescent lamp.
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Rated lamp life is between 5,000
and 18,000 hours, depending on style, approximately five to eighteen times longer than typical
incandescent lamp life.
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Lamps can be selected for desired
colour rendering purpose e.g. aquaria.
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Available with wattage ratings from
4 to 125W. (There are 215W High Output and Powergroove lamps but these will not operate on
conventional European control gear.)
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Low surface brightness provides
better visual comfort and diffused lighting.
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Optional dimmable ballasts are
available. Lamp colour does not significantly change when dimmed. Power consumed is proportional to
light output.
Fluorescent Lamp Disadvantages
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Variations in supply voltage affect
lamp light output and starting.
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Required external equipment
(ballast) consumes energy, adds to equipment cost. For retro- fits, establishes lamp size and
wattages that can be used.
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Lamp frequency flicker can cause
discomfort to some people.
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Operation on a range of supply
voltages requires different control gear components or more expensive tapped ballasts.
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Ballasts may produce irritating
100HZ humming sound - only reliable solution is to replace ballast.
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Lamps are large for the amount of
light produced - HID and incandescent lamps are much more compact.
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Radio frequency interference from
lamps may disturb communications equipment at close range. Note there are new EMC (Electro Magnetic
Compatibility) Regulations due to come into force for the EU.
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Distracting lamp flashing can occur
with a glow starter attempting to strike a failed lamp.
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Stroboscopic effects can make
rotating machinery appear stationary which could be a potentially dangerous situation.
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