Extended ring circuit

[Milleniumaire]

Our house was built 21 years ago and 16 years ago we had a loft extension. The lighting circuit for this appears to have been extended from the upstairs light circuit and the same for the loft sockets.

The consumer unit has a 32amp mcb for the upstairs sockets, which includes the loft sockets and a 6amp mcb for the upstairs lights, which includes the loft lights.

Now for the confusing bit! It was my understanding that the upstairs sockets were on a ring circuit, hence the 32amp mcb. I don't know this for sure, but if it was a radial circuit I would expect a lower rated mcb to have been used eg. 20amp?

I'm considering adding a spur to one of the loft sockets, but wanted to understand how they have been wired up, so I removed the front of each socket. There are 5 sockets in total and to my surprise 4 of them had two cables connected, but one of them only had one cable. Following the cable, where I can (down the eaves crawl space) it runs from one socket to the next and terminates at the socket with only one cable. Isn't this a radial circuit?

I can't determine where the loft socket cable originates, so I'm guessing it has been spurred off the original upstairs ring circuit.

If this is the case, isn't this essentially a spur with 5 sockets? Would this have been acceptable 16 years ago?

5 years ago, as part of a kitchen extension, due to a number of new appliances, the original consumer unit was replaced with a new consumer unit allowing more mcb protected circuits. As part of this work, the house electrics were tested. Shouldn't the "spur" into the loft have raised issues?

What I've found is concerning me enough to not want to add a spur to a loft socket as I don't want to potentially overload the "spur" cable.

Have I got this wrong? Should I be concerned?

 

[AndyPRK]

I think you have it right.

You could change the Mcb to a B25
It will be safe then.

 

[EFLImpudence]

You are more than likely right, but there is one thing missing from your post, which could, but probably doesn't, make everything alright -

the size of the cable.

 

[Milleniumaire]

I can confirm the cable is 2.5mm. This is the same for all the sockets throughout the house, however, the loft sockets were added using white cable, whilst the rest are grey! It made it a little easier to track the loft sockets

 

[AndyPRK]

Is there a 13A fuse plate upstairs that could supply the loft sockets?

 

[Milleniumaire]

I haven't seen a 13a fuse plate anywhere in the loft. Would this be installed at the point at which the new loft spur was attached to the original 1st floor ring circuit? I have been unable to find where this happens - it is probably somewhere under the loft floor and I'm only able to see cable in the eaves due to all the insulation running between the joists.

 

[Milleniumaire]

So, how does a spur of 5 double sockets stand with the current regulations? I assume because it was done 16 years ago, it doesn't need to be changed otherwise the electrician who installed the new consumer unit 5 years ago "should" have picked it up and done something about it.

How would extending a ring circuit into the loft be done correctly these days? I assume it would require a new circuit to be run from the consumer unit, in which case it could be radial or ring, or the 1st floor ring could be extended by "inserting" the 5 loft sockets, running a cable from the final socket back to the original ring circuit, so making an even larger ring circuit as opposed to a 5 socket spur?

 

[terryplumb]

The fused connection unit would probably not be in the loft ,but on the floor below ,as it would need to be on the ring final circuit. It would have made more sense to extend the ring ,or run another circuit in my opinion.

 

[winston1]

Sixteen years ago 5 sockets on a spur in 2.5mm cable was not compliant any more than it is now.

Either of the methods you suggest can be used for loft sockets.

 

[EFLImpudence]

So, how does a spur of 5 double sockets stand with the current regulations?

It is wrong because the cable might be overloaded.
Although, to be honest, this is unlikely.

I assume because it was done 16 years ago, it doesn't need to be changed

No. It was wrong then and it is wrong now.

otherwise the electrician who installed the new consumer unit 5 years ago "should" have picked it up and done something about it.

That is probably unlikely.

How would extending a ring circuit into the loft be done correctly these days?

Use 4mm² cable which is good for the 32A+.
Although this is also unlikely because it involves thinking.
People do what they are used to doing because they are used to doing it therefore that's what they do.

I assume it would require a new circuit to be run from the consumer unit, in which case it could be radial or ring,

There is no point having a ring just for a loft.

or the 1st floor ring could be extended by "inserting" the 5 loft sockets, running a cable from the final socket back to the original ring circuit, so making an even larger ring circuit as opposed to a 5 socket spur?

If you want -

or replace cable with one which can handle the current,
or replace the MCB, 20A will be plenty for upstairs.

 

[Milleniumaire]

Thanks to everyone for their feedback.

Just did a quick calculation this morning and worked out that currently the devices used on the 1st floor/loft socket circuit is around 14 amps. This includes devices that are permanently plugged in, such as TV's and routers as well as other devices that would be used for short periods e.g. trouser press, radiator element, hair dryer, so I think 14 amps would be the current maximum if everything was turned on at the same time.

I'm looking to incorporate two more devices; a sonos connect amp, which uses 2A max and possibly a digital shower (Mira Mode Digital), which requires a 3A FCU. So, potentially, this would take it to 19 amps max, so no real concerns at the moment, other than how to add a spur socket without tagging onto the existing 5 socket spur in the loft!

I checked some of the 1st floor bedroom sockets (all low level) and to my surprise the cables are running into the back boxes from above! I had expected them all to run from below i.e. for the cables to be routed within the ground floor ceiling space/under the bedroom floor. Tried using a cable detector to determine if the cables were dropping down from the 1st floor ceiling, but without success. All 1st floor sockets I checked had two grey 2.5mm cables, so still not found the place at which the loft spur is connected and probably won't if this is under the floor boards connected by a junction box.

 

[winston1]

Thanks to everyone for their feedback.

Just did a quick calculation this morning and worked out that currently the devices used on the 1st floor/loft socket circuit is around 14 amps. This includes devices that are permanently plugged in, such as TV's and routers as well as other devices that would be used for short periods e.g. trouser press, radiator element, hair dryer, so I think 14 amps would be the current maximum if everything was turned on at the same time.

I'm looking to incorporate two more devices; a sonos connect amp, which uses 2A max and possibly a digital shower (Mira Mode Digital), which requires a 3A FCU. So, potentially, this would take it to 19 amps max, so no real concerns at the moment, other than how to add a spur socket without tagging onto the existing 5 socket spur in the loft!

But you will never, ever be using all at the same time. For instance you won't be using the hair dryer while in the shower.

 

[Harry Bloomfield]

Tried using a cable detector to determine if the cables were dropping down from the 1st floor ceiling, but without success.

A metal detector should be able to probe deeper than a live cable detector.

 

[conny]

A metal detector should be able to probe deeper than a live cable detector.

But will probably pick up every bit of extraneous metal like nails, screws and dropped bits of cable in cavities.

 

[EFLImpudence]

and possibly a digital shower (Mira Mode Digital), which requires a 3A FCU.

From what I can find, the device itself is 20W - one twelfth of an Amp.