Halogens With Coverglass Or Without

[EViS]

I need to replace a number of 12v halogen bulbs and have two different styles of lamps.

I have noticed that some of the lamps which utilise a round 'spring' which needs to be squeezed inwards to then remove the bulb, used to have bulbs without a coverglass (Aluminium halogens?).

Whilst other lamps had bulbs with coverglass (Dichronic halogens?).

What is the reason for using halogens without glass in some of these fittings, and can I install halogens with glass instead?

 

[flameport]

If you are talking about the 2 inch round type, they should ALL have a glass front.
If not, when the lamp fails and explodes, pieces of hot glass will fall onto items and people below.

If these are in a ceiling, aluminium reflectors should be used.
If they are being used for display lighting such as in a cabinet where the lamp is fairly close to the object being illuminated, use dichroic reflectors.

 

[EViS]

If you are talking about the 2 inch round type, they should ALL have a glass front.
If not, when the lamp fails and explodes, pieces of hot glass will fall onto items and people below.

If these are in a ceiling, aluminium reflectors should be used.
If they are being used for display lighting such as in a cabinet where the lamp is fairly close to the object being illuminated, use dichroic reflectors.

I am referring to MR16 (GU5.3) halogens, yes. A number of the old bulbs do not have glass in them, and according to this shop, they are available "with and without coverglass".

 

[ericmark]

422.3.1 Except for equipment for which an appropriate product standard specifies requirements, a luminaire shall be kept at an adequate distance from Combustible materials. Unless otherwise recommended by the manufacturer, a small spotlight or projector shall be installed at the following minimum distance from combustible materials:
(i) Rating up to 100 W 0.5 m
(ii) Over 100 and up to 300 W 0.8 m
(iii) Over 300 and up to 500 W 1.0 m
NOTE: A luminaire with a lamp that could eject flammable materials in case of failure should be constructed with a safety protective shield for the lamp in accordance with the manufacturer's instructions.

As can been seen from the Note which is part of the regulations you can't use lamps without the cover unless there is some cover incorporated into the fitting.

Dichroic reflectors with the GZ10 lamps can't be fitted into the GU10 fittings. However there is no such safe guard with the MR16 (GU5.3) range. The dichroic reflector is designed to reflect only light and the heat can pass through the reflector so it will not overheat the item being lit. Considering the small spot is designed to light items like pictures or items in a display cabinet one can understand why one does not want the heat. However today if one was worried about the heat likely one would use a LED or Cold Cathode lamp so really the dichroic reflector is a obsolete idea.

However the UK law and regulations does not stop one buying obsolete and even dangerous items. It only stops one using it unless very special precautions are taken.

In Hong Kong to buy armature radio equipment I needed to show either my passport to show it was to be exported or my licence to show I was able to use in in Hong Kong. However there are no such limitations here and people are allowed to sell equipment which it is illegal to use.

 

[viewer]

You don't say where you're using them, but one reason for having a glass is because these bulbs provide a high level of UV radiation. Not a problem in ceilings but a consideration if close to the eyes.

 

[EViS]

Thanks guys. First time I have ever come across halogens without glass, hence the concern and question. Have purchased replacement bulbs with glass, they are for spots recessed in ceilings.

Have you ever come across such bulbs without cover glass?

 

[mfarrow]

but one reason for having a glass is because these bulbs provide a high level of UV radiation.

Glass isn't UV reflective surely? Otherwise UV tubes wouldn't work.

 

[viewer]

Most glass absorbs the short wavelength UV (UV-C 190 - 280 nm and UV-B 280 - 320 nm), but transmits the longer UV-A (320 - 400 nm) radiation. The UV-B is the region that causes sunburn and skin cancer.
UV-A causes sunburn and tanning. Tanning lamps produce most of their energy at 366 nm and do not produce sunburn except for long exposure times, although the mercury in the tube which emits energy at 366 nm is excited at 254 nm and some of this wavelength passes through the glass. Quartz glass is used where absorption is not desired as in colour chemistry.

 

[ban-all-sheds]

Dichroic reflectors with the GZ10 lamps can't be fitted into the GU10 fittings. However there is no such safe guard with the MR16 (GU5.3) range.

Nearly all lamps with GU10 or GZ10 bases are MR16s.

Quartz glass is used where absorption is not desired as in colour chemistry.

Or where, as for example with tungsten filaments in an atmosphere which has had halogen gas added to it, the temperatures reached are too high for normal glass.