15A rings?!

SSE · Mar 3, 2014

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?

GLENNSPARK · Mar 4, 2014

Pete999 said:
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

i have..in 1.5

and the reason they ran it as a ring was because of the correction factor to be applied to CCC fed from BS3036s (.725)....so a 1.5 radial fed from a 15 A BS3036 wouldn`t comply....would it...

Silly Sausage · Mar 4, 2014

Fig 8ing the L & E legs and taking (r1+r2)/4 at the sockets will reveal more of what's occurring.

Engineer54 · Mar 4, 2014

SSE said:
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.

Not unusual to see industrial 16A commando type socket outlets on 20A ring circuits, certainly had them in the industrial background i came from!!

MDJ · Mar 4, 2014

Certainely making an issue out of this SSE, whats the problem really?

driverman · Mar 4, 2014

On my own home when added extension, new 17th edition. I purposely installed 16amp MCB's on 2 x ring final circuits wired in 2.5mm T & E. And yes in the past I have come across ring circuits wired using 7/029 T&E on 15 amp fuse wire where the expected load is not that great.

Geoffsd · Mar 4, 2014

Surely the point is that we are allowed the standard ring for historical reasons but there is really no reason to design any other kind of ring as whatever you do (and also the standard ring) would be better as two radials.

7029 dave · Mar 4, 2014

If it's worrying you, pull it all down and start belling out end to end on every cable, you will then know for sure. lol

Engineer54 · Mar 5, 2014

Geoffsd said:
Surely the point is that we are allowed the standard ring for historical reasons but there is really no reason to design any other kind of ring as whatever you do (and also the standard ring) would be better as two radials.

I think some would disagree with you there, me being one of them!!

driverman · Mar 5, 2014

Those of you that do new builds with all this insulation in stud walls,behind ceilings in houses as well as in the loft space etc. I understand that 2.5mm cable is downrated to 13amps as enclosed in insulation ie below bedroom floors /above ceilings as cables cross from joist to joist. Therefore the ring would be 2 x 13amps =26amps which is then not suitable for 32amp breaker. Do you guys on new build install 4.0mm cable to overcome problem?