Difference between revisions of "Discharge lighting"

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Sodium & Mercury '''discharge lights''' are used for outdoor lighting. They are widely used as streetlights, and are effective for always-on lighting of large areas.
+
Sodium & Mercury '''discharge lights''' are used for outdoor lighting. They are widely used as streetlights, and are effective for always-on [[:Category:Lighting|lighting]] of large areas.
  
They are highly energy efficient, but the quality of light is poor.
+
They are highly [[:Category:Energy Efficiency|energy efficient]], but the quality of light is poor.
  
Metal halide offers good quality white light, but is not as energy efficient as sodium.
+
Metal halide offers good quality white light, but is not as [[:Category:Energy Efficiency|energy efficient]] as sodium.
  
  
=General Information=
+
==General Information==
The advantages of sodium are extreme energy efficiency and very long lamp life. The disadvantages are poor light quality and slow warm up.
+
The advantages of sodium are extreme [[:Category:Energy Efficiency|energy efficiency]] and [[Lamp Life|very long lamp life]]. The disadvantages are poor light quality and slow warm up.
  
Mercury is much more energy efficient than halogen lamps, but less than sodiums. Mercury lamps are the lowest cost discharge lamps and make good replacements for halogen where light quality is not critical and on times are long. Linear fluorescent lights may also be a suitable option in such situations.
+
Mercury is much more [[:Category:Energy Efficiency|energy efficient]] than [[Halogen Lighting|halogen lamps]], but less than sodiums. Mercury lamps are the [[:Category:Save Money|lowest cost]] discharge lamps and make good replacements for [[Halogen Lighting|halogen]] where light quality is not critical and on times are long. [[Fluorescent Lighting|Linear fluorescent lights]] may also be a suitable option in such situations.
  
Metal halide lamps are costly, but total cost is still less than filament lamps such as halogen, due to their much better energy efficiency.
+
Metal halide lamps are costly, but total cost is still less than filament lamps such as [[Halogen Lighting|halogen]], due to their much better [[:Category:Energy Efficiency|energy efficiency.]]
  
Discharge lamps (light bulbs) are typically relatively expensive to buy, but cheap and highly energy efficient to run. They are very long lived, which minimises relamping.
+
Discharge lamps (light bulbs) are typically relatively expensive to buy, but cheap and highly [[:Category:Energy Efficiency|energy efficient]] to run. They are very long lived, which minimises [[Lamp Life|relamping]].
  
Sodium & mercury lamps take minutes to warm up. Hence they can not be used on PIR detectors.
+
Sodium & mercury lamps take minutes to warm up. Hence they can not be used on [[Dimmed PIR Lights|PIR detectors]].
  
Discharge lights must be run from a suitable ballast, never connect a bulb direct to the mains. The ballast is built into the fitting.
+
Discharge lights must be run from a suitable ballast, never connect a bulb direct to the [[:Category:Electrical|mains]]. The ballast is built into the fitting.
  
 
Sodium lights are available from 18w upwards. An 18w lamp will light more than the average drive or yard.
 
Sodium lights are available from 18w upwards. An 18w lamp will light more than the average drive or yard.
  
  
=Light types=
+
==Light types==
Mercury
+
===Mercury===
* ice cold white light
+
* Ice cold white light
 
* Start time under a minute
 
* Start time under a minute
 
* Sometimes used as street or car park lights, but sodium has become more popular.
 
* Sometimes used as street or car park lights, but sodium has become more popular.
  
Low pressure sodium (SOX)
+
===Low pressure sodium (SOX)===
* pure yellow light
+
* Pure yellow light
 
* Start time in the region of 9 minutes
 
* Start time in the region of 9 minutes
* Exceptional energy efficiency
+
* Exceptional [[:Category:Energy Efficiency|energy efficiency]]
 
* Often used to light motorways
 
* Often used to light motorways
  
High pressure sodium (SON)
+
===High pressure sodium (SON)===
 
* Gives an orangey / golden / pink light.
 
* Gives an orangey / golden / pink light.
 
* Start time in the region of 2 minutes
 
* Start time in the region of 2 minutes
 
* Often used as town centre street lights.
 
* Often used as town centre street lights.
  
Metal Halide
+
===Metal Halide===
 
* Good quality white light
 
* Good quality white light
 
* Available in warm white 2700K and daylight 4000-5000K
 
* Available in warm white 2700K and daylight 4000-5000K
 
* Much better light quality than sodium & mercury lamps
 
* Much better light quality than sodium & mercury lamps
 +
* Relatively high purchase cost
  
  
=Colour Perception=
+
==Colour Perception==
 
Under low pressure sodium light, since only one colour is produced, vision is monochrome, meaning no perception of an object's colour is possible. The viewer's perception of colour under these lights is due to light from other sources, memory, and the awreness that greens and blues will look dark while orange and yellow appear light.
 
Under low pressure sodium light, since only one colour is produced, vision is monochrome, meaning no perception of an object's colour is possible. The viewer's perception of colour under these lights is due to light from other sources, memory, and the awreness that greens and blues will look dark while orange and yellow appear light.
  
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Mercury discharge lamps produce white light, but the spectrum is not high CRI, and the relative brightness or intensity of different colours is not natural. Although this is the closest of the 3 to white light, it is a perceptually less pleasant light than high pressure sodium.
 
Mercury discharge lamps produce white light, but the spectrum is not high CRI, and the relative brightness or intensity of different colours is not natural. Although this is the closest of the 3 to white light, it is a perceptually less pleasant light than high pressure sodium.
  
The combination of both mercury and high pressure sodium lamps gives a much better quality of light than either lamp alone. To be visually acceptable, the 2 lamps must be in the same place, hence this strategy is best suited to high positioned lamps lighting large areas.
+
The combination of both mercury and high pressure sodium lamps gives a much better quality of light than either lamp alone. To be visually acceptable, the 2 lamps must be in the same place, hence this strategy is best suited to high positioned lamps [[:Category:Lighting|lighting]] large areas.
  
 
Metal halide lamps give a true white light.
 
Metal halide lamps give a true white light.
  
 
For more information on the spectra of these lamps and the implications for vision, see
 
For more information on the spectra of these lamps and the implications for vision, see
 +
* http://www.lamptech.co.uk/Documents/SO2%20Spectral.htm
  
http://www.lamptech.co.uk/Documents/SO2%20Spectral.htm
 
  
 
+
==Luminous Efficacy==
=Luminous Efficacy=
 
 
Typical figures, in lumens per watt. Filament lamp performance is included for comparison.
 
Typical figures, in lumens per watt. Filament lamp performance is included for comparison.
* 180 Low pressure sodium
+
* 180     Low pressure sodium
 
* 110-150  High pressure sodium
 
* 110-150  High pressure sodium
* 50-125 Metal halide
+
* 50-125   Metal halide
* 35-60 Mercury discharge
+
* 35-60   Mercury discharge
* 10-17 Filament
+
* 10-17   Filament
  
  
=Fittings=
+
==Fittings==
 
Discharge lighting fittings typically look more industrial than domestic. 18w SOX fittings that look like bulkhead lights are available.
 
Discharge lighting fittings typically look more industrial than domestic. 18w SOX fittings that look like bulkhead lights are available.
  
==Transplant==
+
===Transplant===
 
If you want something that looks better, the contents of an ugly fitting can be transplanted to a fitting of your choice.
 
If you want something that looks better, the contents of an ugly fitting can be transplanted to a fitting of your choice.
 
# Buy the necessary luminaire for your chosen lamp
 
# Buy the necessary luminaire for your chosen lamp
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Note:
 
Note:
* Don't try to transplant metal halide, the starting voltages involved are much too high for non-purpose designed fittings and standard cable. Transplants are only for sodium and mercury.
+
* Transplants are only for sodium and mercury.
 +
* Don't try to transplant metal halide.
 +
** The starting voltages involved are much too high for non-purpose designed fittings and cable.  
 +
** Metal halide fitting must be able to contain exploded bulbs.
 
* The wattage rating of the light fitting should exceed that of the lamp being used by a good margin.
 
* The wattage rating of the light fitting should exceed that of the lamp being used by a good margin.
 
* Don't use a fitting with a mirror finish reflector, this can cause lamp overheating. Light scattering reflectors are ok.
 
* Don't use a fitting with a mirror finish reflector, this can cause lamp overheating. Light scattering reflectors are ok.
* Do not attempt to operate discharge lamps from PIR sensors. Timers and dawn to dusk sensors are suitable.
+
* Do not attempt to operate discharge lamps from [[Dimmed PIR Lights|PIR sensors]]. Timers and dawn to dusk sensors are suitable.
  
 
For SON and mercury only:
 
For SON and mercury only:
* Keep the wire between ballast and bulb short.
+
* Keep the [[Cables|wire]] between ballast and bulb short.
* This wire will have to cope with high voltage starting pulses with some of these lamp types, so use a heavy mains flex.
+
* This [[Cables|wire]] will have to cope with high voltage starting pulses with some of these lamp types, so use a heavy mains flex.
  
  
=Lighting Options=
+
==Lighting Options==
For domestic use a PIR operated 150w halogen lamp or better a few PIR operated CFLs are generally the best option. They give white light and are only on a small amount of the time. 500w of of halogen is much too bright for the majority of houses.
+
For domestic use a [[Dimmed PIR Lights|PIR]] operated 150w [[Halogen Lighting|halogen lamp]] or better a few [[Dimmed PIR Lights|PIR]] operated [[CFL Lamps|CFLs]] are generally the best option. They give white light and are only on a small amount of the time. 500w of [[Halogen Lighting|halogen]] is much too bright for the majority of houses.
  
Mounting a halogen high up reduces glare. Mounting it within reach of a window makes relamping easy.
+
Mounting a [[Halogen Lighting|halogen]] high up reduces glare. Mounting it within reach of a [[:Category:Glazing|window]] makes [[Lamp Life|relamping]] easy.
  
If a PIR light would spend a lot of time on in your situation, a low power sodium lamp on a timer and/or a dawn-dusk sensor may produce lower total energy use and less bulb changes. The price is lower light quality.
+
If a [[Dimmed PIR Lights|PIR]] light would spend a lot of time on in your situation, a low power sodium lamp on a timer and/or a dawn-dusk sensor may produce lower [[:Category:Energy Efficiency|total energy use]] and [[Lamp Life|less bulb changes]]. The price is lower light quality.
  
For large yards a good policy is often a combination of minimal low pressure sodium lighting plus halogen or CFL on PIRs.
+
For large yards a good policy is often a combination of minimal low pressure sodium lighting plus [[Halogen Lighting|halogen]] or [[CFL Lamps|CFL]] on [[Dimmed PIR Lights|PIRs]].
  
  
=See also=
+
==See also==
http://en.wikipedia.org/wiki/Lighting_efficiency
+
[[Category:Lighting]]
  
http://members.misty.com/don/light.html
+
[http://en.wikipedia.org/wiki/Lighting_efficiency Wikipedia Lighting Efficiency]
 +
 
 +
[http://members.misty.com/don/light.html Don's Expert Lighting Site]
  
 
[[Lighting Glossary]]
 
[[Lighting Glossary]]
  
 +
[[Rewiring Tips]]
 +
 +
[[Special:Allpages|Wiki Contents]]
 +
 +
[[Special:Categories|Wiki Subject Categories]]
  
  
Line 114: Line 124:
 
[[Category:Electrical]]
 
[[Category:Electrical]]
 
[[Category:Energy Efficiency]]
 
[[Category:Energy Efficiency]]
 +
[[Category:Save Money]]

Revision as of 10:13, 29 May 2007

Sodium & Mercury discharge lights are used for outdoor lighting. They are widely used as streetlights, and are effective for always-on lighting of large areas.

They are highly energy efficient, but the quality of light is poor.

Metal halide offers good quality white light, but is not as energy efficient as sodium.


General Information

The advantages of sodium are extreme energy efficiency and very long lamp life. The disadvantages are poor light quality and slow warm up.

Mercury is much more energy efficient than halogen lamps, but less than sodiums. Mercury lamps are the lowest cost discharge lamps and make good replacements for halogen where light quality is not critical and on times are long. Linear fluorescent lights may also be a suitable option in such situations.

Metal halide lamps are costly, but total cost is still less than filament lamps such as halogen, due to their much better energy efficiency.

Discharge lamps (light bulbs) are typically relatively expensive to buy, but cheap and highly energy efficient to run. They are very long lived, which minimises relamping.

Sodium & mercury lamps take minutes to warm up. Hence they can not be used on PIR detectors.

Discharge lights must be run from a suitable ballast, never connect a bulb direct to the mains. The ballast is built into the fitting.

Sodium lights are available from 18w upwards. An 18w lamp will light more than the average drive or yard.


Light types

Mercury

  • Ice cold white light
  • Start time under a minute
  • Sometimes used as street or car park lights, but sodium has become more popular.

Low pressure sodium (SOX)

  • Pure yellow light
  • Start time in the region of 9 minutes
  • Exceptional energy efficiency
  • Often used to light motorways

High pressure sodium (SON)

  • Gives an orangey / golden / pink light.
  • Start time in the region of 2 minutes
  • Often used as town centre street lights.

Metal Halide

  • Good quality white light
  • Available in warm white 2700K and daylight 4000-5000K
  • Much better light quality than sodium & mercury lamps
  • Relatively high purchase cost


Colour Perception

Under low pressure sodium light, since only one colour is produced, vision is monochrome, meaning no perception of an object's colour is possible. The viewer's perception of colour under these lights is due to light from other sources, memory, and the awreness that greens and blues will look dark while orange and yellow appear light.

High pressure sodium produces a wider spread of colours, but still an incomplete spectrum. Much more colour perception is possible. Red orange yellow and green are visible, but blue is almost absent.

Mercury discharge lamps produce white light, but the spectrum is not high CRI, and the relative brightness or intensity of different colours is not natural. Although this is the closest of the 3 to white light, it is a perceptually less pleasant light than high pressure sodium.

The combination of both mercury and high pressure sodium lamps gives a much better quality of light than either lamp alone. To be visually acceptable, the 2 lamps must be in the same place, hence this strategy is best suited to high positioned lamps lighting large areas.

Metal halide lamps give a true white light.

For more information on the spectra of these lamps and the implications for vision, see


Luminous Efficacy

Typical figures, in lumens per watt. Filament lamp performance is included for comparison.

  • 180 Low pressure sodium
  • 110-150 High pressure sodium
  • 50-125 Metal halide
  • 35-60 Mercury discharge
  • 10-17 Filament


Fittings

Discharge lighting fittings typically look more industrial than domestic. 18w SOX fittings that look like bulkhead lights are available.

Transplant

If you want something that looks better, the contents of an ugly fitting can be transplanted to a fitting of your choice.

  1. Buy the necessary luminaire for your chosen lamp
  2. Buy the light fitting you want to transplant the lamp into
  3. Transplant the bulb holder from luminaire to chosen fitting
  4. Connect the 2 with mains flex
  5. Mount the luminaire somewhere out of sight

Note:

  • Transplants are only for sodium and mercury.
  • Don't try to transplant metal halide.
    • The starting voltages involved are much too high for non-purpose designed fittings and cable.
    • Metal halide fitting must be able to contain exploded bulbs.
  • The wattage rating of the light fitting should exceed that of the lamp being used by a good margin.
  • Don't use a fitting with a mirror finish reflector, this can cause lamp overheating. Light scattering reflectors are ok.
  • Do not attempt to operate discharge lamps from PIR sensors. Timers and dawn to dusk sensors are suitable.

For SON and mercury only:

  • Keep the wire between ballast and bulb short.
  • This wire will have to cope with high voltage starting pulses with some of these lamp types, so use a heavy mains flex.


Lighting Options

For domestic use a PIR operated 150w halogen lamp or better a few PIR operated CFLs are generally the best option. They give white light and are only on a small amount of the time. 500w of halogen is much too bright for the majority of houses.

Mounting a halogen high up reduces glare. Mounting it within reach of a window makes relamping easy.

If a PIR light would spend a lot of time on in your situation, a low power sodium lamp on a timer and/or a dawn-dusk sensor may produce lower total energy use and less bulb changes. The price is lower light quality.

For large yards a good policy is often a combination of minimal low pressure sodium lighting plus halogen or CFL on PIRs.


See also

Wikipedia Lighting Efficiency

Don's Expert Lighting Site

Lighting Glossary

Rewiring Tips

Wiki Contents

Wiki Subject Categories