Ring spurred at origin?

[mattrgee]

Hi all,

DIYer here. My garage has a double socket fed by 4mm2 twin and earth connected to the same circuit breaker has the ring main for the sockets upstairs in the house. The MCB is a B32.

Is the feed in the garage considered a spur from the ring main or is it a separate radial circuit which happens to be on the same MCB? Ideally I'd like to add more sockets to the circuit in the garage (using 4mm2) but is this safe or allowed?

Thanks.

 

[Spoon]

Just interested - how long is this 4mm spur cable?

Considering the 4mm is connected at one end at the CU (located in the garage) and to a socket at the other end (also located in the garage) I'm presuming it's not that long, unless the garage is massive and the route is silly.

 

[MDJ]

Duel post, no idea why, apologies

 

[MDJ]

Ah okay thanks for the reply, I did wonder, that explains your post
It will be fine though

 

[Midwest]

Is this because it's on a B32 MCB?

Considering the 4mm is connected at one end at the CU (located in the garage) and to a socket at the other end (also located in the garage) I'm presuming it's not that long, unless the garage is massive and the route is silly.

Perhaps its the same guy, who had the bathroom in his bedroom the other day; or was it a bedroom in his bathroom?

 

[Risteard]

I wouldn't agree that the 4mm^2 part of the circuit needs to be considered as an unfused spur from the ring final circuit at all.

In my view it is clearly a hybrid ring/radial final circuit and in no way is it one of the standard circuits.

Assuming that the 4mm^2 cable is afforded overload protection by the 32A circuit breaker then it isn't unsafe to add sockets to the radial part of the hybrid circuit.

Presumably it was done because spare ways were not available or whatever. As I stated before my concern with the arrangement is solely the fact that there is unlikely to be an adequate connection/clamping of all the circuit conductors when they are of varying cross-sectional areas, and for this reason I would consider the arrangement to be wholly unsatisfactory.

 

[Midwest]

Perhaps he run out of 2.5mm and only had 4mm on his van?

 

[HandySparks]

As I stated before my concern with the arrangement is solely the fact that there is unlikely to be an adequate connection/clamping of all the circuit conductors when they are of varying cross-sectional areas, and for this reason I would consider the arrangement to be wholly unsatisfactory.

I wouldn't dismiss a connection of two different cable sizes out of hand. I think that it depends entirely on the skill and conscientiousness of the person doing the job and the type of terminal involved. I've seen a pigs ear made of terminating a standard 2.5mm² ring, and I've also made a decent job of terminating different cable sizes into the same terminal.

 

[Toneyz]

Thanks all.

Tempted to leave it as is for the time being and not add any additional sockets. There's a bathroom renovation on the cards soon where there is an electric shower running from a dedicated circuit. Once that has been decommissioned I'll ask he electrician to create a dedicated circuit for the garage sockets.

I think that this would be a good idea.

 

[Toneyz]

Adding/altering this existing circuit would not be notifiable.

It used to be didn't it, as I remember on the NICEIC building control notification website having a box to tick for additions?

 

[MDJ]

What was the problem again?

 

[Lucien Nunes]

As I see it:
There is no need to apply the '1 point' limit to the radial. That limit is imposed to avoid overloading the spur cable (normally the same size as the ring cable and hence unprotected against overload by the OCPD) and to avoid concentrating the load on the ring itself at a single point partway along. Neither circumstance applies here as the 4mm² is not undersize for the OCPD nor connected partway along the ring.

I am with Risteard in that my only real concern would be the 2 x 2.5 + 1 x 4.0 terminated in the CU terminals. Whether it is likely any worse a connection than 3 x 2.5 not very nicely done in the back of a socket-outlet, is moot. It's not a standard circuit configuration and might automatically be non-compliant, unless the 'alternative methods of equal safety' concept applies.

I wouldn't say inserting an FCU in order to add more socket-outlets would make it materially safer. It might technically make it slightly less safe as the fuse in the FCU would be potentially prone to long slight overload as are all FCUs feeding multi-point spurs, a situation which ought to be avoided if possible, without offering any benefit to the protection of the circuit (which is already OK). It would however make it compliant apart from the possible objection to the mixed cables in the termination.

 

[westward10]

This is what I was saying in #3 and 11.

 

[ipf]

This is what I was saying in #3 and 11.

There see. A bit of common sense explained to strict reg readers...source of the ring but still against regs?
Answer. Interpret as you will...but don't forget to think.

 

[MDJ]

This is what I was saying in #3 and 11.

where does it say 3 and 11 mate, I cannot see the post numbers on my puter.

 

[Risteard]

and the type of terminal involved.

We know that it is a cage clamp terminal as that is what BS EN 60898 etc. stipulate. So I can't see a good way of doing this into such a terminal.