Based on annual running costs for 4,000
hours (@8p per kw /h)
Factors not included:
Lamp cost:
Lamp life: GLS - 1000 hrs HAL -Halogen - 2000 hrs M/Hal - Metal Halide - 6,000 hrs Mbf - Mercury - 16,000 hrs Son - Sodium - 24,000 hrs Sox - 16,000 Maintenance and lamp replacements
Cost of Fitting:.Starting time requirement
Colour Rendering
Lamp
Colour Temp. (K)
Colours enhanced
Colours subdued
.
SON
2100
yellow orange
blue green red
yellow
functional
GLS
2700
orange red
blue green
"cosy" warm
HAL
2900
orange red
blue green
"crisp" warm
MBF
4000
blue green
yellow red
neutral
white
M/HAL
5000
blue green
.
fresh
active
.
5000 +
.
.
daylight
Lamp Types
Halogen Lamp
A short name for the tungsten-halogen lamp. Halogen lamps
are high
pressure incandescent lamps containing halogen gases such
as iodine or
bromine which allow the filaments to be operated at higher
temperatures
and higher efficacies. A high-temperature chemical reaction
involving
tungsten and the halogen gas recycles evaporated particles
of tungsten
back onto the filament surface.
High-Intensity Discharge (HID) Lamp
A general term for mercury, metal halide and high-pressure
sodium lamps.
HID lamps contain compact arc tubes which enclose various
gases and metal salts
operating at relatively high pressures and temperatures.
High-Pressure Sodium (HPS) Lamp
HPS lamps are high intensity discharge light sources which
produce light by an
electrical discharge through sodium vapor operating at relatively
high pressures and temperatures.
Incandescent Lamp GLS
A light source which generates light utilizing a thin filament
wire
(usually of tungsten) heated to white heat by an electric
current
passing through it.
Mercury Lamp
A high-intensity discharge light source operating at a relatively
high
pressure (about 1 atmosphere) and temperature in which most
of the light
is produced by radiation from excited mercury vapor. Phosphor
coatings
on some lamp types add additional light and improve colour
rendering.
Metal Halide Lamp
A high-intensity discharge light source in which the light
is produced
by the radiation from mercury, plus halides of metals such
as sodium,
scandium, indium and dysprosium. Some lamp types may also
utilize
phosphor coatings.
Other Terms
Average Rated Life
The median time it takes for a lamp to burn out. For example,
a 60-watt
Soft White bulb can be expected, on the average, to burn for
1,000
hours. Based upon continuous testing of lamps in laboratories,
the
1,000 hour rating is the point in time when 50% of the test
samples have
burned out and 50% are still burning.
Lumen
The international (SI) unit of luminous flux or quantity of
light. For
example, a candle provides about 12 lumens.
A 60-watt Soft White incandescent lamp provides 840 lumens.
Lumens Per Watt (lpW)
A measure of the efficiency, or, more properly, “efficacy”
of a light
source. Efficacy is easily calculated by taking the lumen
output of a lamp
and dividing by the lamp watts. For example, a 100-watt lamp
producing
1750 lumens has an efficacy of 17.5 lumens per watt.
Typical lamp efficacies:
Edison’s first lamp ............................................................................
1.4 lpw
Incandescent lamps ............................................................................
10- 40
Halogen incandescent lamps .............................................................
20- 45
Fluorescent lamps ............................................................................
35- 100
Mercury lamps ....................................................................................
50- 60
Metal-halide lamps ...........................................................................
80- 115
High-pressure sodium lamps ..........................................................
100- 140
Note: the values above for discharge lamps do not include
the effect of the ballasts which must be used with those lamps.
Taking ballast losses into account reduces “system”
or lamp-ballast efficacies - typically by 10-20 percent depending
upon the type of ballast used.
