Why does my lighting circuit fuse blow every time a bulb "blows" and needs replacing?

Question

The 5A Consumer Unit Fuse blows too, very annoying, especially if I don't have a spare......

Answer 1

I suggest that you replace the rewireable fuses with miniature circuit breakers of the same ratings, or at least fit one to the offending circuit. You will be able to get a 5 or 6 amp MCB. This will probably still trip when a lamp 'blows' but will be easier for you to reset. (Just like a switch) MCB's are actually more sensitive than rewireable fuses, if you can get a 5/6 amp type C instead of the more common type 'B' it will resist this type of fault better but will still protect the lighting circuit.

Some light bulbs are more prone to internal shorts, usually imported from eastern europe, Ajax etc. You could also try using better quality lamps. Osram/GE/Crompton/Philips etc. These better lamps will have internal fuses in the caps which should blow before your fuse in the consumers unit.

Answer 2

scotts right but here is what you can do turn off the 2 pole breaker that feed the subpanel in the garage ( the 2 pole breaker is the one with the pin between the 2 breakers, this is called a tie bar, and will trip if one of the 2 legs -1 per pole - has a ground fault ). remove all the fuses in the sub panel ( it's not energized since you turned of the 2 pole breaker ) in the garage. make sure all light switches are off and anything that is plugged into an outlet is unplugged. now go back to the main panel, turn on the 2 pole breaker.. does it hold and not trip, then the wires from the main panel to the sub panel might be ok, with no dead short. now turn it off again. go pack to the sub panel in the garage ( it's not energized ), screw in one good fuse fuse ( 15 amp? it probally better that it be a 15 amp than a 20 amp just in case you wires are not 12 guage but 14 guage ). go back the main panel, turn on the 2 pole breaker, does it hold.. good turn it off and repeat. sooner or later you'll find a glass fuse that will either blow or the 2 pole breaker trip. you could also do the very same thing with only 1 good 15 amp glass fuse by screwing it in on the next free socket after find the previuos one did not blow. even if you did all this and then no fuses blow, then one by one turn on any light switch, and plug in something ( nothing of value but something that draw currnet ) into any normal looking receptacle, as it could be a the device along ( say a cheap fqan motor ) has the short ( of a hanging florescent strip light ) and not the light switch or the actual receptacle. once you have identified the offneding circuit, call an eletricain and let him know what you have found, from there he can trace for the dead short on the given circuit. whatever you do NEVER replace a smaller amperage glass fuse ( 15 amps for example ) for a larger one ( say a 30 amp glass fuse )m unless you are familair with wire size and ampacity there of, it safer to go with a lesser rated fuse until you know for CERTAIN, the wire size ( guage ).

Answer 3

The reason it happens is because when the filament burns out a small section if the filament vapourises, the bulb temprarily has tungsten vapour present which conducts electricity. For a short time this vapour causes a short circuit between the filament terminals

Answer 4

Due to a brief power surge in the circuit when the bulb blows.

(It is very annoying especially if your fuze box is in a cupboard behind loads of stuff, it is pitch dark when the bulb goes and your torch is out of batteries)

Answer 5

Your bulb holder is defective. Its getting shorted intermittantly when you insert the bulb into it. A total fault has not yet developed. Just replace the bulb holder and you will get rid of the problem.

Answer 6

Because the blown bulb breaks the circuit and trips the switch xxx

Answer 7

Good grief!! Just happened to me, and it is a real pain especially when it's dark.

Answer 8

It's a built in safety thing but very annoying!!