Incomplete ring circuits?

[Dustydazzler]

It’s fairly common to find an open rings or a big spur ring where it was a ring and someone has added multiple Extra sockets off a single spurred cable So you have multiple sockets on a single 2,5 cable

from what I have seen on youtuber electricians most of then now just swap out the 32a mcb for a 20a mcb rather than try to put all the sockets back on a complete ring

but that imo is a bit lazy and you are reducing The Ccc of the circuit which Could have originally be designed to supply the whole house worth of sockets on a 32a ring circuit

 

[pc1966]

That is a simple and cheap "fix" as you say, but not very elegant or professional.

Still, if the usual suspects from the kitchen (washing machine, dishwasher, etc) are on a different circuit I doubt most houses would draw 20A for the remaining sockets (unless they rely on a lot of plug-in electrical heaters, of course).

 

[telectrix]

that's on reason for radials in the living/bedroom areas of a house. rare to see more than 5 -10 A anywhere except kitchen/utility rooms. RFC is the logical choice for the latter.

 

[mattg4321]

Maybe 10% of rings I test are open or very poor reading. No real difference in whether it’s L,N or CPC.

Never seen thermal damage due to open ring, and I’ve probably come across 100+ open rings over the years

 

[radiohead]

I swapped a 32a device for a 20 on a recent job simply because rectifying the multiple spurs off spurs was going to be expensive and damaging. It's not always unprofessionalism, just the need to remedy at reasonable cost. I feel what is often forgotten on this forum in a rush to condemn a less than perfect solution is that not all clients can, or want to pay for the ideal when there is a cheaper way.

 

[Strima]

The amount of discontinuous conductors on a ring will probably be the same as any other circuit, except people notice when half of their radial sockets stop working and do something about it.

 

[Lucien Nunes]

Which means that they usually get rectified, whereas the rings might not until the next EICR. Therefore if the probability of a connection being open is equal for rings and radials, EICRs would tend to reveal a disproportionately high number of faults on rings.

I previously raised the third question and no-one reponded with a confirmed case of thermal damage. I think there is a logical reason why none will be found. Cable CCC is based on a working temperature that will enable the cable to provide a good working lifespan under continuous load. It will withstand short excursions to significantly higher temps and is only likely to sustain visible damage if the insulation softens so much that it deforms at the connections or the conductors or cleats migrate through it. Any cable installed so that Iz is sufficient for a 32A RFC, will probably carry the full 32A by itself (or clear a fault on a B32) without this happening. It will remain in the zone where its working life and its ability to withstand mechanical damage is reduced, but won't actually disintegrate unless otherwise stressed e.g. by crushing. Since most general-purpose and domestic socket-outlet circuits are only ever fully loaded for brief periods, the reduction in durability will not tend to have any real impact and the cables will appear unharmed.

 

[cliffed]

I’ve seen spec 4.00mm,mainly conduit cabling in schools.
If you go up another size you wont get the conductors in.
2.5 mm just the jobby.
Recently did a school block,spec,rings in classrooms,T&E,everywhere else radials 20amp 2.5mm

 

[pc1966]

Also with rings I expect the majority of opens only impact on live conductor, so other other is still current-sharing as a ring and you don't have the full 32A thermal effect on one leg even if most of the loads are there.
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It's not always unprofessionalism, just the need to remedy at reasonable cost.

My apoligies for that wording. On reflection it is not the right thing to say and as you point out sometimes making it safe at an affordable price is by far the best action.

 

[mattg4321]

With regard to switching out a 32a mcb for a 20a, how do you all feel about a live conductor potentially floating around in a back box somewhere if this has been done because there is open circuit rather than multiple sockets from same spur off ring