Incomplete ring circuits?

[pc1966]

The recent click-bait thread on radial vs ring final circuit descended in to the usual arguments ranging from sane to near-religious, but one issue that was raised among the general noise is the risk of a ring with an open somewhere.

So I wondered if the folk on here that do many EICR and similar work could comment on the following:

• Roughly what percentage of tested RFC do you see with an open ring?
• Is there any more common fault than other (e.g. is E more likely to be open than L, etc)?
• How often are those incomplete rings showing any sign of thermal stress / overheating?

And please folks keep the thread discussion on this one point of open rings, not the general merits of RFC vs Radial, etc.

TL;DR Open ring, any common cause and does it overheat?

 

[ChrisElectrical88]

Id say of all the circuits I test 2% have an open ring so about 1 in 50.
I’d say 20% have a off reading so line and neutral not the same or CPC >1.67 that of the line and neutral.

Ive not commented on the other thread, cause it’s just daft. Both circuits have their uses. I actually wired a 32A 4mm ring last week, it’s the first time it’s been practical to do so with a fully clipped direct run.

 

[radiohead]

I think a 'survey' on open rings will inevitably depend on the type of properties people are testing. I find a lot of broken rings in 60's-70's houses with original and invariably altered wiring, and recently attended a fault where no less than 3 outlets had burnt out/damaged line terminations, the cause being a combination of loose terminations and increased load due to a break in r1. I would suggest a high percentage of such properties have RFC faults. I suspect those who test mainly commercial or industrial find far fewer broken rings

 

[pc1966]

Id say of all the circuits I test 2% have an open ring so about 1 in 50.
I’d say 20% have a off reading so line and neutral not the same or CPC >1.67 that of the line and neutral.

That is interesting, as that is picking up bad connections as far more of an issue than complete opens.

Ive not commented on the other thread, cause it’s just daft. Both circuits have their uses. I actually wired a 32A 4mm ring last week, it’s the first time it’s been practical to do so with a fully clipped direct run.

Exactly!

Oddly enough my current work has a 32A RFC of 12 double sockets in 4mm simply because most other circuits need 4mm, so no point in buying some 2.5mm as well.

It also has 6 outdoor sockets for occasional maintenance use as two radials, also in 4mm for voltage drop reasons, but on a 20A MCB due to the rating of the isolator switch.

 

[Dannyboybl00]

Over the past year I reckon 20% of the EICRs I've done (around 50) have revealed an open ring. All but two have involved neutral and CPCs with the breaks being due to poor connections at a socket (or weak CPCs snapping in a backbox). Not seen any thermal damage as yet.

 

[pc1966]

I would suggest a high percentage of such properties have RFC faults. I suspect those who test mainly commercial or industrial find far fewer broken rings

I suspect many properties of the 60s/70s coming up for sale now as old folk die or move in to retirement homes will have had no EICR at all, and a lot of dubious changes to make up for a lack of adequate provision of sockets by today's standards.

But as you say industrial and commercial tend to have more professional modifications and inspection/maintenance over the years.

 

[ChrisElectrical88]

That is interesting, as that is picking up bad connections as far more of an issue than complete opens.


Exactly!

Oddly enough my current work has a 32A RFC of 12 double sockets in 4mm simply because most other circuits need 4mm, so no point in buying some 2.5mm as well.

It also has 6 outdoor sockets for occasional maintenance use as two radials, also in 4mm for voltage drop reasons, but on a 20A MCB due to the rating of the isolator switch.

Yes there are defiantly a lot more poor connections than open rings. I mainly test social housing which are maintained, erm I’ll say ‘averagely’ well. So the lads doing to works should be competent enough.
I do like the idea of 32A 4mm radials everywhere, however it doesn’t take much to de rate 4mm below a 32A current carrying capacity.
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I should add that I did 2 years solid of testing Pubs a few years ago and in that environment getting a good ring was about 50/50 chance.

 

[pc1966]

Certainly I suspect that bad connections are more likely to be a source of thermal damage than simply the loss of one of the live conductors' continuity.

That is an issue for both RFC & radial, though we have AFDD to save the day.

Stop laughing at the back, you with the torque screwdriver!
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I should add that I did 2 years solid of testing Pubs a few years ago and in that environment getting a good ring was about 50/50 chance.

How odd, I would have expected them to be much the same as other commercial/industrial properties. Maybe those wanting to be pub landlords know more dodgy Dave DIYers to get work done?

 

[ChrisElectrical88]

How odd, I would have expected them to be much the same as other commercial/industrial properties. Maybe those wanting to be pub landlords know more dodgy Dave DIYers to get work done?

Pubs are a different breed altogether. We would do a 20% test of the installation each year. In most cases I was getting the last 20% so all the rings were left as the years before the lads had just opted for the easier radials. Lots of adapted circuits, countless spurs on spurs. Pubs are awful. Still it’s rare I’ve seen any thermal damage on a ring.

 

[Taylortwocities]

Maybe those wanting to be pub landlords know more dodgy Dave DIYers to get work done?

I do work for a local landlord. He’s a tenant and is supposed to use the maintenance team from the brewery for jobs. But the maintenance team are
1. Crap
2. Come from the brewery 200 miles away. The landlord gets charged for time which includes travelling, so it’s expensive.
in my case I’m a trusted cheaper supplier for him and I get served first at the bar when it’s busy!

 

[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.