Old fuse

My mate has just moved house and when he tried to connect the cooker he found the fuse is missing.

Does anyone recognise this fuse and maybe can advise where a replacement can be purchased?

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Thanks for any help

Brian

Reply to
Brian Drury
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The fusebox needs replaceing, the lower right contact has been damaged. I suspect that there may be also other issues with wireing that is that old.

Reply to
James Salisbury

It's standard MEM of many years ago. Think I've got a complete secondhand one lying around which you're welcome to if your anywhere near Balham.

Reply to
Dave Plowman (News)

Well looking at

I'd say your mate has rather more problems than just a missing fuse.

The signs of overheating on the bottom terminal and the single blue wire behind the meter fixing stand out as being "interesting". Then there's the earth wires with no sleeving and what appears to be a bit of two core flex...

I would leave the cooker disconnected until you've found out why the fuse was missing.

I test installations for a living and if I found something like that, I would look very thoroughly at the rest of the installation.

Sorry,

John

Reply to
John White

The message from "James Salisbury" contains these words:

Which may well be why the fuse was removed in the first place.

Reply to
Guy King

That is a 30A wired fuse and, as wired fuses should be derated to 65%, it should not be carrying more than about 20A. It is not suitable for connecting a cooker. That fuse box needs to be replaced with a consumer unit, using MCBs or, at least, cartridge fuses. The rest of the installation should also be checked. While the box may well be older than the cables running from it, there are aspects that suggest that, if the house was rewired, it was not recently. In any case, a house with one lighting fuse, one fuse that probably feeds an immersion heater, one power circuit fuse and one cooker fuse, is probably rather short of power points by today's standards and would benefit from a rewire because of that.

Colin Bignell

Reply to
nightjar

Does this apply to my fuse box that has wired fuses, built in 1978 ish?

I have never heard of the de-rating of wired fuses before. Though I am no electrician.

Dave

Reply to
Dave

Some confusion here -- conductors protected by rewirable fuses need derating by 66%, not the fuse or appliance. So any cable protected by this 30A fuse should be rated at 45A.

Reply to
Andrew Gabriel

That depends on whether you are adding a new cable to an existing fuse or trying to ensure adequate protection to an old circuit, that probably was installed using 30A rated cable.

Colin Bignell

Reply to
nightjar

And there's me been a good boy and just bought myself a replacement CU with RCD and MCB's because I thjought it was a good idea and sensible to have an RCD. I had no idea that cables shuld be derated if covered by a wired fuse - that is quite a bombshell and will encourage me to get on with the changeover.

What is the group philosophy on the Company Fuse - do I again be a good boy and get them in or do I just ignore them and cut the seal? And if it is the latter I won't tell who said so !! I once did a CU change with the tails live but access was easy and my own one isn't quite so accessible.

Rob

Reply to
robgraham

Actually the factor is 72.5% (see Appendix 4 of BS 7671) so the tabulated current rating required is a shade over 41 A, assuming no other rating factors apply. This is met by 6 mm^2 T&E cable, if clipped direct, and that is most probably what is installed here.

In the days when rewireable fuses were the norm the tabulated cable current ratings were given for what was then called "coarse overcurrent protection" - these had the derating factor built in and no further derating was required. If you had "close overcurrent protection" you were allowed to /up/rate the cables by 33%.

Pre-metric cooker circuits would have been installed using 7/0.036, rated at 31 A or 7/0.044, 37 A, ('coarse' clipped direct ratings for PVC twin) so would have been OK on a 30 A BS 3036 fuse with no derating required.

Reply to
Andy Wade

Chances are the cable size is adequate on the original installation if properly done. Re-wirable fuses were normally 30 amp for rings using 2.5mm cable and 5 amp for 1mm lighting circuits. And protected perfectly well for many a year. ;-)

Reply to
Dave Plowman (News)

Do it properly and "arrange a temporary disconnection." See

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information pertaining to your particular DNO.

Reply to
Andy Wade

Also noticed after I posted that I'd said "derating by", rather than "derating to", sigh.

Reply to
Andrew Gabriel

err.. is it just me or does it look like that piece of two core flex is wired directly off the isolator switch - so what will that be 60A or 100A on a 2.5mm flex? I would get that looked at ASAP

Reply to
MadJen

It's hard to tell without seeing the bottom bit of the unit. but I'd interpreted it as having the neutral connected in the usual way and the live going into the 5A fuse in the bottom left along with the 1.0 mm wire.

I also suspect it's 0.75 mm twin flat flex rather than 2.5mm

Yes. In fact I'd get the whole installation looked at ASAP

John

Reply to
John White

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