DIY Doctor

Light Bulb & Fitting Getting Extra Hot

Postby dowtish » Sun Aug 22, 2010 9:08 pm

Just changed the light bulb in my kitchen recently as the old one died...... left the light on while pottering round the house and when I came back light had gone off and there was a slight smell of burning.

Replaced bulb with an old 100w non-energy efficient..... had the light on for about 5 mins and it was extremely hot to touch (bulb & fitting).

Wondering if I there is an issue with my electrics (don't want the house to burn down).

Prior to this I've never had any issues!

Anyone know what the problem could be?

Many thanks
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Simply Build It

Postby ericmark » Mon Aug 23, 2010 4:31 pm

This is why we use discharge lighting I will not call it energy saving as it only saves energy if you don't want the heat.

A tungsten bulb give out light and heat and the latter uses all three forms to dissipate conduction, convection and radiation. The latter is very good since it does not heat the air but heats your body direct so drafts do not stop it working. So with tungsten lamps you can reduce the temperature of the air and still feel warm so used correctly during the winter they save energy as you run your central heating less.

However it also gets rid of heat by convection and for that to work there needs to be enough air flow. To ensure there is enough flow the shades are normally marked as to their maximum wattage often around 60W and many shades will over heat with a 100W bulb.

Of course with no shade and 9 inches of flex there is little problem but as you have them closer to ceiling and restrict the air flow then there is a fire risk.

Normally when the bulb blows it just stops working but of course on the odd time it can break and the bits inside can start a fire where they land on the floor. Old shades tended to be under the bulb so it would catch the bits should that happen plus of course and moths etc.

Also as the get so hot the solder contacts can over time malform and make it very hard to remove the bulb.

Because they are so hot any water like rain can also break the glass so they have to be protected from water when used outside.

As to energy saving when I talked to Energy saving trust they said the discharge lamp does save energy when used outside and there will be a point where air changes mean the two types of lighting cross over as far as saving energy but no tests have been made to work out at what point each type of light becomes the best for energy use.

With the extra production costs and mercury use I feel the government were wrong to stop production of old types of bulb especially where electric can be made with renewable sources but this option is not open for the gas used in central heating.
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