Luminaires

Question 1

Explain luminous intensity distribution

Answer 1

It is the extent to which the flux is distributed in different directions from the luminaire.

Question 2

How is luminous intensity distribution controlled

Answer 2

Using reflectors and prismatic deflectors

Question 3

How is glare controlled?

Answer 3

Louvres across the face of the luminaire ensure a cutoff. Some flux is directed away from the luminaire to the walls and ceiling to reduce contrast. This resulted in very little flux reaching the walls, so high contrast and gloomy appearance. This is less of a problem now that screens are less reflective.

Question 4

Explain maintenance factor

Answer 4

Because some lamps particularly LED with decrease in output slowly. LEDs will decay faster if they are allowed to overheat. In a group of lamps it is likely that some will fail faster. Output will also be reduced through a buildup of dirt on diffusers and reflectors. The rate at which the output decays involves depends on a number of factors and cannot always be predicted accurately.

Maintenance factor is a multiplier that we use to over-light the space at the beginning so the space will still be lit to the design level for a longer period of time.

Question 5

What is the formula for total lighting maintenance factors

Answer 5

Lamp lumen mf x lamp survival factor x luminaire mf x room surface MF