bulb blew and "wrecked" the fuse holders!

[Allthumbs]

SWMBO switched on the light and "bang, it was like an explosion" she said. "oh yeah" I said. Went downstairs and said "blimey etc" the G9 halogen bulb had disappeared except for its base, there was a layer of powdered glass on everything and when I looked at the fuse box the fuse and the adjacent fuse were half pushed out of their holders. The *adjacent* fuse holder base was obviously cracked. Questions:- IIRC Can I buy new fuse holder bases (this is old style wire fuses) rather than a whole consumer unit? Is this type of rather drastic blown fuse and scattered glass a feature of the halogen bulbs? (I don't fancy it again, might change kitchen light to something else).

(will not tackle till tomorrow as up all night watching tennis, like to be fresh for electrics!)

[John]

Can you let the group know the manufacturers name (of the fusebox)

[NT]

If its wylex, yes

yes, its one reason halogen lights shold always have a tough glass cover.

NT

[Adrian]

NT gurgled happily, sounding much like they were saying:

I've never come across it - OK, not a HUGE sample, but a fair few 12v &

240v halogen bulbs. None of the fittings in the house have "tough glass covers". Or, indeed, any covers at all.

[Lurch]

Yes, but look at upgrading to HRC fuses at least, or MCB's.

It's a feature of the old style BS3036 fuses you have got "protecting" your wiring. It takes a much larger current to blow a rewirable fuse than it does to blow an HRC fuse or trip an MCB. It's not a kitchen light problem, it's an outdated electrics problem.

[Dave Liquorice]

Halogens can go with a helluva bang. You don't want to be in the firing range if one decides to fail that way, red hot, molten, silica glass at high velocity.

[cynic]

The size of the bang depends on a number of factors but comes down to the "available" fault current from the supply through the wiring and faulty item. Rewirable fuses are wide open to abuse such as wrong size of wire being fitted, multiple strands of correct wire, previous failures depositing a conductive copper coating on the carrier etc. As you mention it being a lighting circuit it is usual to find a 5Amp fuse with white colour code spot - is yours such? This is why cartridge fuses were preferred until the advent of circuit breakers although it was sometimes possible to fit overrated cartridges to some designs. If you have a Wylex consumer unit replacement fuse holders are still available in rewirable or cartridge styles or alternatively "plug in" circuit breakers of appropriate ratings. If your consumer unit is another make you may struggle to get hold of new replacements but you may get a used item from a sparky.

[Andrew Gabriel]

Yes, they don't have anywhere to include a fuse in the bulb.

It sounds like your supply impedance is low enough for the fault current to exceed the breaking capacity of BS 3036 rewirable fuses, so the fuse "broke", i.e. it failed to safely disconnect the supply because the current flowing through it was too high. Breaking capacity of BS 3036 varies depending how they were wired, but it is much lower than that of any MCB or cartridge fuse you would buy today. I would suggest changing the CU for a modern one which is spec'ed for your supply (probably need at least 6kA breaking capacity given your experience, but this needs measuring). As a temporary repair, buy fuse carriers which take BS1361 cartridge fuses, rather than a new rewirable fuse carrier.

[NT]

Its not a common occurrence, but its a known problem. Sometimes the hot pieces can set fire to things.

Most halogen bulbs have an outer glass cover as part of the bulb. Some types don't though, such as capsule bulbs and linear halogen. As you rightly point out, those are sometimes used with no cover. In some countries such fittings are not legal.

NT

[Allthumbs]

[Allthumbs]

yep, shall not get the type of fitting again

[Allthumbs]

yep, with 5amp wire in it!

[Allthumbs]

OK, thanks, good idea

[Allthumbs]

These look like the thing, comes with a new base (which I need)

"

"do they replace (inc base) without needing to disconnect all the output/input cables?

[Allthumbs]

just been down the DIY shed and I see they plug in simply, great! Will get a set of the tripper type replacements from somewhere that actually has some stock (not my local B&Q)

Thanks for all the help, this honestly is the best group on usenet IMHO.

[fred]

In article , Allthumbs writes

That's them.

Yes, the blades of the new cartridge based fuseholder mate with the old leaf sprung contacts of the fusebox. Removing the holder exposes the contacts but they are isolated by the main switch (do check though, take care and wear safety specs).

At those prices, you can afford to replace the lot. Make sure you get plenty of spare fuses.

[RobertL]

We had a problem with a (new) cooker. it went 'bank' and managed to blow not only the wire fuse, but also the big cartridge fuse that is before the meter thu scutting off all electricity to the house. that was when I decided to have a modern CU fitted.

Robert

[Andrew Gabriel]

Also note that a 5A BS1361 fuse that these take is same size as a 5A BS1362 plugtop fuse, but don't use a BS1362 plugtop fuse in the consumer unit - it doesn't have a high enough breaking capacity.

[Andrew Gabriel]

The MCB's which plug in to Wylex style CU's also have rather low breaking capacity - IIRC, something like 3kA for the toggle ones, and 1kA for the push button ones. Given you've already had a BS3036 rewirable fuse destroyed due to having too low breaking capacity for your supply, I would stick with BS1361 cartridge fuses.

If you want MCBs (tripper type), you should replace the whole CU with a modern one.

[<me9]

Probably get them from TLC. I did not very long ago.

Be aware teh plug in MCBs are only rated for 3KA breaking capacity. This is enough in most domestic situations but not all. It is, however, more than the re-wireable ones .