Document Sample
Lighting Powered By Docstoc

This subject is an engineering discipline all on it’s own. For this reason, the subject shall be

Types of lighting.
There are many types of ‘lighting’, ranging from incandescent to ‘low energy fluorescent’ to EMR

The current trend is to move away from inefficient incandescent lighting. Incandescent lighting,
even while it’s ‘colour’ is ‘easy on the eye’, is quite inefficient with regard to power consumption
compared to that of other types.

Fluorescent Lighting.
This lighting is by far the most common. Unfortunately, fluorescent lighting is still predominantly
used with the ‘old style’ inductive ballasts. These inductive ballasts are generally available in 2
types – High Power Factor & Low Power Factor. High Power Factor ballasts are usually about Cos
 0.95 or 0.9. Low Power Factor ballasts are about Cos  0.5. Always choose the High Power
Factor ballasts. An alternative to this is the use of ‘electronic ballasts’, which are very energy
efficient but a little more expensive.

The colour of the globe is also important. These colours are generally expressed as numbers ie 820
to 860. For ‘warmer’ lighting, choose a lower number. ‘Warmer’ lighting is very good for colour
rendition. A standard colour globe is 840.

Generally speaking, a high quality globe will last at least 30 000 hours (about 4 years if not
switched off) if used with an electronic ballast. Cheaper globes will last about 8 000 to 15 000 hours
(if not switched off). The ‘switch on/switch off’ life of a fluorescent globe is reduced if used with
an inductive ballast. This affect is almost eliminated if an electronic ballast is used.
If possible, try to use Tri-Phosphor globes…they have a very long life (30 000 hours).

Low Voltage Lighting.
Low Voltage Lighting (32 volts or less) is commonly misunderstood. This lighting will use the
same amount of energy as higher voltage lighting (Ohms Law), therefore money savings about this
lighting, are a myth. As a matter of fact, it may cost you more in electricity to use this lighting. The
reason being is that this lighting requires the use of transformers to change the voltage from 220
volts to 12 volts. Most of these transformers are crudely made & dissipate about half of the used
energy as heat. The usual energy loss with these transformers is about 45%. This means that you
will be paying almost double the amount of electricity to use this lighting. Also, these transformers
have been known to cause fires because they become very hot.

On the other hand, if used with electronic ballasts, the efficiency is quite ok.

The other factors of this lighting are also largely misunderstood. The globes are usually Halogen,
which means that they generate significant amounts of heat. Also, even though they may seem to
emit ‘more light’, the light emitted is usually only in an arc that does not exceed 55 degrees. This
fact makes this type of lighting ‘directional’. In other words, they are good for ‘spot lights’ but not
good for general lighting to a large area. It is a misconception that these lights are better than other
lights. It must be realised that lighting is specific to a required function.
                                       External Lighting.

External lighting (outside & in the ‘weather’) is generally more expensive than internal lighting. All
external lighting should have an Ingress Protection rating of at least 55. For example, if an external
lighting fixture has an IP55 rating, it’s ok. Essentially, an IP55 rating means that it is ‘weather
proof’. IP65 is better. All light fixtures/fittings should not be installed externally if the IP rating is
less than IP55. The same rating applies to ALL electrical appliances.

Most external lighting is Quartz Iodine, Sodium Vapour or Mercury Vapour. Quartz Iodine (QI) is
the cheapest but is not efficient. Sodium Vapour or Mercury Vapour is quite expensive but quite
efficient. Mercury Vapour & Sodium Vapour lights cost substantially more than the QI lights.
Mercury Vapour lights give a ‘blue-ish’ light whilst Sodium Vapour give an Orange light. Mercury
Vapour is the best for colour rendition.

                                         Light dimming.

ALL incandescent lights are dimmable along with most Halogen lights (QI lights are incandescent).
Fluorescent, mercury vapour & sodium vapour lights are NOT dimmable. The same applies to most
modern ‘low energy’ lights…they are NOT dimmable. To try to dim these lights usually results in a
total failure of the light or a greatly reduced life.

Shared By:
Tags: Light
Description: Lighting