Blown fuse in main fuse box

[rogerr]

Hi, The fuse has blown to our downstairs lights. I know how to fix it but, from looking on the internet, people are saying we should first check for the cause.
We have a bungalow with a loft conversion (with a separate fuse box) and a flat roofed extension, so can't get to see much of the wiring--the only way would be to rip up the floorboards upstairs or if the cause is in the flat roof, we would have to pull the ceiling down!!
Can a fuse just wear out? --we have lived here 23 years and have never had to change any of the fuses before.
Any help/advice would be greatly appreciated.

[theshedman]

Hi rogerr, I am not an electrician but when our lights blow I reset the switch and look for the one which caused it to blow, usually the one that doesn't come back on. Then it is usually just a case of putting in new bulb. If it does it again and it's the same one blowing the fuse then it is normally a fault or loose wire in that particular fitting at either the light holder end or the switch itself. Then you should be able to either fix it or get new fitting. If you are not sure about doing it yourself get a electrician in and he will test it for you. Good luck.

[rogerr]

Thank you so much--I will do exactly that.

[rogerr]

Thanks shedman, it was exactly as you said. By sheer coincidence both light fittings off one switch blew at the same time--they usually take it in turns to blow!
Cheers, Barbara

[theshedman]

Hi Barbara, glad that I could help.

[Tweed]

Fuses (FUSEWIRE or cartridge based fusewire) can wear out. They are designed to tolerate a particular current, but can handle a much higher current if subjected to it for a short enough time but it will degrade the fusewire over time.

You should replace fuse/wire and bear in mind that there may be a fault and look out for it, i.e. switch off all lights on the dodgy circuit before returning power and then turn the lights on individually to see if a particular light causes the fault. If the fault is other than a degraded fuse then it will present itself pretty quickly by blowing the replacement fuse and then you know you have a more serious fault. See theshedmans answer :)

Does the fuse blow when all lights on circuit are on? Yes - then too many lights, and/or too much current being consumed for that circuit.

Normal design (when I was in the game) is max 10 lights per circuit rated at (Av.) 100 watts per fitting, or 1 kW(ish) per 5A circuit.

[rogerr]

Many thanks for the extra info Tweed.

[woodchopper]

Our fuses use to blow every time a lamp blew -stopped buying cheap bulbs and hasn't done it since.