15A rings?!

[SSE]

Went to swap over an old fuse board yesterday, whilst I was removing it there seemed to be 3 ring circuits each protected by a 15A fuse. There was two live ends coming from each fuse. Tested each of the live, neutral & earth end to see if there was continuity & there was. Now, there aren't a lot of sockets on each circuit, the first one has 8 sockets including the kitchen sockets, but the only appliances that are in the kitchen & that would draw a large load is really the fridge. The other "ring" is for the ground floor which only has 7 sockets. There is a tumble dryer & washing machine run on this circuit, plus TV, Sky etc, again not too much load. The final circuit which is the 1st floor & 2nd floor has 7 sockets on it again no big loads at all, just two TV's. The thing I can't understand is why someone would have a 15A ring?! The installation is fairly old & I'm sure by looking at bits that there's been a fair bit of DIY done. You would think with the washing machine etc being on at same time it would blow the fuse? It wasn't until I had went back today & thought that maybe the fuse-wire had just been changed to 30A fuse wire, sadly when I went to check all the old gear has been dumped! I thought about tracing each cable but when I went to take the sockets off the lengths on each wire are so short I really think I'd struggle to get them back in! My obvious worry is that if I fit a 30A & it's not a ring the cable could overload. I crossed over my L & E at the board & went round each socket to see what sort of readings I was getting but to be honest it was up & down readings. Slightly puzzled to say the least. anybody came across anything similar?

 

[Pete999]

It's a pity you couldn't get hold of the fuse carriers, it's quite possible as you intimate that a larger size fuse wire was installed, sadly we can never find out. As for the "rings" and your assumption that there has been a DIYer at loose, again without proof we will never find that out either, but to answer your question, no, Ihaver not come across RFCs on a 15a fuse before, my guess would be an ill informed DIY merchant, sorry, can't be of any more help

 

[Rockingit]

The concept of a ring can apply to any size or value of circuit, the fact that we're used to talking about them in relation to a 30/32A domestic is irrelevant. So long as the cable and CPD are appropriately sized, it's all fine.

I've often thought that probably the real capacity of a 2.5mm ring is more than 32A (given that 6242Y 2.5 is good for 29A) but probably not as high as 40A so we have to settle for a 32A breaker as that's the nearest available.

I've never done the calculations (and don't intend to start now!) but my guess is that there are all kinds of weird and wonderful combinations of capacity available on different cable sizes - it's just not worth the bother to install them though as there's no practical gain.

 

[SPARTYKUS]

Did you ascertain the cable size on these rings? Maybe it was wired using 1.5mm2 T+E :mickey:

 

[Octopus]

Maybe the breaker value was all the installer had on them!

 

[jaypp]

spurs from spurs could have lead to fuses being adjusted accordingly. was there pattern to 'up n down' readings?

 

[SPARTYKUS]

Good point jaypp

 

[Richard Burns]

I had a house with two socket rings one was on a 32A and one was on a 20A, no idea why, the rings both tested out fine, no spurs, and I decided that since it had been working fine for ages I would not change it.

 

[SSE]

Did you ascertain the cable size on these rings? Maybe it was wired using 1.5mm2 T+E :mickey:

Definitely 2.5mm twin & earth!

Maybe the breaker value was all the installer had on them!

Well the lazy **** should have went back & changed it when he got the chance to save me scratching my head! lol.

spurs from spurs could have lead to fuses being adjusted accordingly. was there pattern to 'up n down' readings?

No, pattern at all. Some values are very similar then the odd on is at least twice the value of the others.

I had a house with two socket rings one was on a 32A and one was on a 20A, no idea why, the rings both tested out fine, no spurs, and I decided that since it had been working fine for ages I would not change it.

See I was maybe thinking about just leaving them as 20A rings as at least if these were radials joined or spurs from spurs etc the cable should then be protected?

 

[Adam W]

My uncle had 15A plugs and sockets in his house until he sold it in the late 90s. He preferred them. Presumably 15A sockets would be protected by a 15A protective device, and that the first thing the new owner did was change the socket fronts for 13A ones.

 

[jaypp]

the odd on is at least twice the value of the others.

i think it needs further investigation. others may be able to give more help. like to hear findings. all the best

 

[Marvo]

My uncle had 15A plugs and sockets in his house until he sold it in the late 90s. He preferred them. Presumably 15A sockets would be protected by a 15A protective device, and that the first thing the new owner did was change the socket fronts for 13A ones.

The 15A round pin plugs aren't fused which might get a bit hairy when they're plugged into a standard UK 32A rfc. The 15A plugs are standard where I am but we run sockets on 2.5mm radials with 20A ocpd.

 

[Engineer54]

The 15A round pin plugs aren't fused which might get a bit hairy when they're plugged into a standard UK 32A rfc. The 15A plugs are standard where I am but we run sockets on 2.5mm radials with 20A ocpd.

The old BS 15A sockets are still commonly found in many countries, especially those that were once British colonies or protectorates. Even in some of those countries, that have since adopted the 13A socket outlets. They use them to supply the bigger load appliances like Air Conditioners, immersion heaters etc, or in kitchens for built in appliances the under worktops supplied by FCU.

Those old 15A plug tops certainly contain a damn sight more brass than the American or European 16A equivalents, and probably good for a lot more than the stated 15A's too ...lol!!

So maybe much to many here's surprise, they are still very much alive and doing very well overseas... Believe it or not, even here in China!! ...lol!!

 

[Rockingit]

We still use them in theatres to this day, for exactly the reason (apart from tradition) of being unfused and realistically very hard to overload (at a guess I'd say you could probably get twice the rating out of them before getting too hot, in fact the cable would go first). People have slowly switched over to 16A ceeform as it's an easier and more available format but 15A is still very much alive. You'll also find many schools and village halls with lighting installs using 5A due to restrictions on supply.

 

[SSE]

My worry is that it's not a ring & like has been says is spurs off spurs which have somehow become some sort of ring giving continuity. Safest option until it can be further investigated to put it them on 20A MCB's? Really not sure.