Dichroic Lamps

[OJM]

I want to install a set of low voltage downlighters in my kitchen, but have heard a number of people complain about the frequency that the bulbs seem to need replacing. Can anyone recommend the best bulb type to use, and what is Dichroic?

 

[securespark]

Dichroic is the type of lamp used, amongst others, by selv light fittings.

It refers to the reflector part of the lamp, which is multi-faceted and coated to give good reflectance.

As existing posters will know, I am firmly an Osram man. My personal experience has been excellent, and the very few returns I have had (2 in total) have been replaced under warranty, NQA.

 

[Big_Spark]

I can concur with Simon about the quality of Osram products, far better than the others.

 

[AdamW]

When bu**ering about with my bathroom I managed to knock both lightbulbs with removed wall studs and the own-brand one smashed with barely a tap. The branded one (think it was GE) took several whacks and still worked fine when I tried the switch afterwards. And it was the bulb that was here when I moved in 2 years ago.

Branded definately do offer a long-term advantage.

 

[journeyman]

Dichroic lamps have a reflector which reflects most of the visible light forward and allows most of the infra-red heat to pass through the back of the lamp.

Low voltage Dichroic lamps give out almost twice the light of conventional reflectors of the same wattage. With the combined effect of the dichroic reflector and the increased efficacy, you will have a lot less heat thrown onto the object that is lit,, for a given light output.

It is best to use individual transformers for each halogen light. A dimmer will help increase the life of all lamps. But you must use dimmable transformers and dimmers suitable for LV lighting.

Halogen lamps rely on a self recycling process to make them last longer, dim them too much and this process stops. It is wise to turn the dimmer up full every so often to recycle the lamp.

 

[journeyman]

addendum:

Dimming a halogen lamp will loose some of the of the benefits:

High efficiancy.

Crisp white light.

 

[OJM]

Dichroic lamps have a reflector which reflects most of the visible light forward and allows most of the infra-red heat to pass through the back of the lamp.

Something else that I need to consider is the heat generated by the lamp as I will be placing the lamp holders in to a ceiling that is insulated with Celotex type insulator, (foam sheet with foil outer). If a Dichroic lamp allows heat to pass through the back of the lamp, then that suggests that the lamp holder may get warmer than if the heat from the lamp was directed forward.

 

[journeyman]

All recessed lighting will give heat backwards, dichroic or not. There must be sufficient space left around the fittting for heat to escape. The installation instructions shouldl tell you you what is required.