Ring main.

[JKMRK1]

Question I have is, is it ok to have x2 ring main circuits on one 32amp type B MCB??

If so does this meet the current regs.

TIA.

 

[Mark Wright]

Going the other way round and this is from a European web site

"The rules for ring wiring say that the rated current of the cable must be at least two-thirds of the rating of the protective device. This means that the risk of prolonged cable overload can be considered minimal. However, in practice it is very rare to find a ring with a different protective device than a 30 A fuse, a 30 A circuit breaker or a 32 A circuit breaker and a cable with a cross-section different from the one mentioned above."

right or wrong what's the common response to finding a Ring on a 20A MCB or wired in 4mm??

 

[ipf]

Just a point.
Two rings or not, in general, what are FIRST thoughts on four (or more) cables in a circuit breaker terminal, whilst carrying out an EICR?
How long is a piece of string, maybe?

 

[radiohead]

Just a point.
Two rings or not, in general, what are FIRST thoughts on four (or more) cables in a circuit breaker terminal, whilst carrying out an EICR?
How long is a piece of string, maybe?

It would depend on an informed engineering judgement as to whether the conductors were securely terminated for me.

 

[James]

Just a point.
Two rings or not, in general, what are FIRST thoughts on four (or more) cables in a circuit breaker terminal, whilst carrying out an EICR?
How long is a piece of string, maybe?

It says to me that things have probably been done on a tight budget, i.e. the consumer unit has not got enough ways for what they want to supply.

look out for other things that may have been overlooked!

 

[DPG]

It says to me that things have probably been done on a tight budget, i.e. the consumer unit has not got enough ways for what they want to supply.

look out for other things that may have been overlooked!

But there's a spare way in this particular CU.

 

[radiohead]

Tell me about it did think it would get so many mixed opinions! Always tell myself it doesn't hurt to have a second opinion on things and as I wasnt certain about this that's what I done. Thank you for the positive outlook and advice ?

I dont think you have got mixed opinions, nobody has said this is anything other than bad practice. But the question concerns regulations, and as yet nobody has given an actual regulation that this breaches, and throwing hands up in horror does not count as a regulation.

 

[ChipFanDave]

For all we know it could only be two double socket outlets in the circuit.
I propose we call these bow-tie final circuits from now on!

 

[James]

But there's a spare way in this particular CU.

Still, tight budget could also mean tight on time, not got another breaker in the box?
never mind, its Friday the pub is open, just stick it in the other breaker and we are out of here!!
when you see an obvious short cut like that it makes me look for others.

 

[Risteard]

You could put more than one radial on a MCB but its not good practice.

You couldn't, because by definition it would be one radial.

2 Rings on 32mcb is dangerous are you sure it's not 2 radials?

How is it dangerous, apart from the potential issue with the four conductors in the terminals/cage clamp (which although crap is unlikely to be an issue in real terms)?

 

[DPG]

Still, tight budget could also mean tight on time, not got another breaker in the box?
never mind, its Friday the pub is open, just stick it in the other breaker and we are out of here!!
when you see an obvious short cut like that it makes me look for others.

Yep, fair point.

 

[SparkyChick]

I fully agree that this is incorrect and should not have been done.

But having said that what are the apparent dangers? I don't see any particular danger attributable to this.

The definition of a circuit is based around everything that is connected to a single way in a distribution board, so this would still count as one circuit, although it is nom-standard.

@Pete999 , Dave has summed up my own personal view to a T.

If both of the rings are correctly installed and the cables sized correctly, then I'm struggling to see how this arrangement would be any more dangerous than each of them connected to their own MCB, sure from an isolation point of view it's less than ideal, but from a safety perspective I don't see how it's any less safe than a ring final running from it's own 32A MCB. If you were talking two ring circuits supplied by two MCBs with one leg of each ring in each MCB, that's another matter (have seen this and nearly got bit by it, thankfully my chicky sense started tingling and I did another check at the socket I was working on).

And I'll reiterate what I said... I personally wouldn't do it, except as maybe a temporary solution to restore supply in the event of say an MCB or RCBO failure. But I think it's an interesting thought exercise because I'm not sure what regulations it would be breaching. The closest I can come to is largely dependent on how you define circuit.

Just a point.
Two rings or not, in general, what are FIRST thoughts on four (or more) cables in a circuit breaker terminal, whilst carrying out an EICR?
How long is a piece of string, maybe?

Absolutely, it's not good, and it would be a C3 from me, unless there were clear signs of bad connections (loose cables, heat damage etc.) in which case it would be a C2. My reasoning... does it present a danger now or would it present a danger if something else happened? Potentially it might, but so would any ring final circuit and I'm thinking broken or poor end to end continuity or some other error in installation.

But like I said, I'm just curious about peoples thought processes and reasoning. We can't remember everything and we certainly can't know everything so it's an interesting topic for debate
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right or wrong what's the common response to finding a Ring on a 20A MCB or wired in 4mm??

Could be a long cable run, the 20A MCB could be a left over from a broken ring when someone downgraded it to be safe, the 4mm could be there because the Zdb at the source of the circuit was too high for 2.5mm to cut it from a Maximum Zs perspective, or in extreme cases even a maximum NL loop impedence perspective.

But if it was safe and compliant, I'd just be asking myself why?

I did a rewire job last year and ran a ring in 4mm. It was a mistake on my part... I picked up the wrong reel and just cracked on. Was a costly mistake, but hey ho

 

[pc1966]

Ugly but not dangerous. This circuit, not me (but close enough)

In terms of overload you can overstress the 32A MCB on a ring with only 4 items plugged in, so unless this was conjoining two rings that had been chosen to separate high-demand loads it is not really any worse than a bigger single ring.

What is curious is why was this done? The OP says there is one slot free so probably this was a temporary fix for a failed MCB that has become permanent.

 

[ipf]

It would depend on an informed engineering judgement as to whether the conductors were securely terminated for me.

You could probably make sure on that if reconnecting after testing. Available breaker? Terminal and c/b condition? Circuit condition? General install condition?
Like I say, how long's a piece of string?
Definitely needs improvement though, probably C3, dependant upon what it leads to.

 

[DPG]

Ugly but not dangerous. This circuit, not me (but close enough)

In terms of overload you can overstress the 32A MCB on a ring with only 4 items plugged in, so unless this was conjoining two rings that had been chosen to separate high-demand loads it is not really any worse than a bigger single ring.

What is curious is why was this done? The OP says there is one slot free so probably this was a temporary fix for a failed MCB that has become permanent.

Exactly. I would be doing some testing before going any further.

 

[ipf]

Ugly but not dangerous.

Hey, be careful! You don't know who's lurking.