FUSING DETAILS FOR DISCHARGE CIRCUITS

LOUVRE CATEGORISATION (LG3)

he addendum to Lighting Guide 3 (LG3), is concerned with the visual environment for display screen use. There has been a great deal of coverage of this new publication in the lighting press, with alarmist stories heralding the death of the 'Cat 2' luminaire. However, LG3 was first introduced in 1989 and revised in 1996, taking into account new technology, more advanced screen types and modifications to International Standards. The current guide is 62 pages in length and gives comprehensive guidance concerning considerations that ought to be taken into account when designing lighting installations in spaces where computer equipment will be used.

Two of the current 62 pages of LG3 detail the luminaire category rating system, i.e. Categories 1-3, under the section 'designing with direct lighting'. However as it has became the 'norm' amongst some in the industry to specify 'Cat 2' luminaries without consideration of the environment into which they are installed, the new Addendum to LG3 states that the luminaire category rating system is withdrawn. This must not be misconstrued as an outright condemnation of category 1, 2 and 3 luminaries, nor is it suggested that category luminaries can no longer be used in commercial interiors. They can. The message within the new guidance is to ensure that designers and installers focus specifically on both the needs of the end-users and the interior in each case, designing the lighting accordingly.

It is important that, where possible, questions are asked of the client/end-user as to the type and use of display screen equipment. This is important, since screen technology and software have both advanced considerably since the first introduction of LG3. Where new display screen equipment is used, such as those with a TFT screen using positive polarity software, the maximum luminance recommendation for the luminaire can be increased significantly. (Note, the new addendum will be aligned to the International Standard BS EN 29241 'Ergonomic requirements for office work with visual display terminals', in terms of the three ISO monitor classes defined and considered).

The key to success is attaining a harmonious balance of luminances within the space in question. It is particularly undesirable to have wide variations or rapid changes in luminances across an office interior. The choice of lighting hardware should always bear this in mind. A regular array of recessed luminaries with a sharp-cut off installed within an interior with dark furniture and a dark floor finish, will invariably suffer from a gloomy appearance due to inadequate upper wall and ceiling luminances. Yet the same space, with the careful selection of additional wall-washers and uplighters, will be vastly improved in terms of visual appearance. We must never lose sight of the fact that we are lighting for people and thus we should endeavour to create lighting installations that enable the tasks in question to be performed in a pleasant an environment as possible.

Products which should be considered in order to meet the recommendations of the addendum to LG3 include:

Eclipse - page 6.8

Ecostar - page 3.11

Elite - page 7.1

Lotus - page 7.12

Paragon - page 6.7

Softlux - page 7.11

LIGHTFORM:

Area - page 12.22

Classic Pendant - page 12.13

Eyeliner - page 12.16

Mercurio - page 12.17

Slenderline - page 12.24

Starwash - page 12.28

Sytos - page 12.15

UFO - page 12.11