max lighting wattage

[twitchy]

i am under pressure to fit some new light fittings which have multiple bulbs i.e. 6 x 40W and wondered what the maximum should be on a standard lighting ring(already got some in place). My memory of these in the past has been that bulbs tend to blow really regularly, and I wondered if this was connected.

Any advice?

 

[pcboffinuk]

Twitchy,

The maximum you can have is generally determined by the fuse/mcb that you have protecting your circuit - most modern lighting circuits are on a 6A MCB - at 230V that gives you a maximum of 1380W. Assuming you don't have dozens of lights already attached, the extra 240W this fitting would add shouldn't be a problem but you would need to check. (I believe you are allowed some diversity because not all lights are expected to be on at once but I don't have the book to hand to check exact figures at this time of night).

Whether you need 6 x 40W bulbs is another matter, unless its a big room you may find that too bright.

Exceeding the maximum for the lighting 'ring' (actually lighting is (almost) always a radial circuit not a ring) would cause the fuse/MCB to blow, but not the bulbs.

One thing that can cause it is if you have a high voltage - my house runs at 247V, which is still within the allowed limits, but if you use bulbs rated at 230V then the life will tend to be shorted. Of course, other problems with the wiring can also cause it...

Hope that helps - feel free to ask if you are unsure. I am sure others will add their wiser and more experienced words of advice...

Gavin

 

[Steve]

Other factors that contribute to short lamp life are excessive vibration, poor quality bulbs, frequent switching, excessive heat. I'm sure there are more.

 

[plugwash]

try replacing the switches if it hasn't been done recently, i belive old switches are often a cause of bulb failure.