Installing additional sockets on spur

[Bugwug]

Hi,

Am after some feedback please. My house is pre 1860, has a consumer unit so has been upgraded at some point in 90's or early 2000's, I have been here since 2004.

Today I was going to install 2 additional twin power sockets in my front room when i discovered that the adjacent socket on other side of the room that i was going to extend the ring from was actually a spur (as it only has one cable entering it, from the ceiling)

The 3 sockets in the upstairs of the property also only have one cable so again would seem spurs, I am unable to verify the 2nd socket in the front room as its behind a heavy desk.

The consumer unit has a separate trip for Shower, Lights, Mains.

So, without being able to verify the remaining 4 or 5 sockets in the house, I can imagine that these are all spurs from a Junction box in the ceiling linking back to the CU (as there is not a multitude of connections otherwise so has to be a Junction somewhere)

Would it still be ok to fit the additional sockets to the original spur (which has now worried me hence asking) as in reality i have been running all the entertainment appliances for the last 8 years or so from this socket on extension cables anyway or, would it be seriously bad and I should really look into renewing all the electrics which is not going to be a this holiday job and lots of money I don't have but understand if that's the response.

I know in an ideal world I should upgrade, but I want to to this responsibly and was supposed to be a Christmas holidays project so I could then redecorate, feel like I have opened a can of worms now!

Many a thanks

Natalie

 

[Chri5]

Pay £150-£200 for a sparks to do an EICR- electrical installation condition report.

Then go from there.

The circuits could be radials, which tend to be identified by looking inside the fuse board. A ring has two cables, a radial only one.

Have a look at the diynot wiki for further info if you wish.

 

[EFLImpudence]

They can't all be radials.

It would appear that the 'ring' runs around the first floor floor-space with all the sockets spurred from it.

So you can either do the same or -
alter the run so that the ring runs through the new sockets or -
add as many sockets as you want spurring from an existing socket but you must install a 13A fused connection unit before and to protect all of the sockets on the spur.

 

[Bugwug]

Hi Chris,

Thanks for response. I thought all circuits had to be Ring these days so am a bit relieved that Radial is something that exists, although I was not aware of it previously and so was concerned I had a bunch of spurs and potentially dangerous wiring.

I looked at the Wiki articles which were useful, many thanks for pointing them out.

What would be the advantage (aside from less cabling) of a Radial wiring compared to Ring which is what I was expecting to find.

Ta

Natalie

 

[PrenticeBoyofDerry]

Have you got access to the ceiling void where the connection are coming from.
It sounds very likely and not that unusual (but bad practice) that the sockets have been spurred from either a radial or a ring final circuit and connection made within the void.

If you could confirm the connection and circuit type, it could be possible to install additional sockets, this may mean you need to extend the circuit or add fused connection units.
But more investigation is required.

 

[AndyPRK]

what size breaker for the sockets is in the CU ?

16,20,32A ?

 

[PrenticeBoyofDerry]

I thought all circuits had to be Ring these days so am a bit relieved that Radial is something that exists, although I was not aware of it previously and so was concerned I had a bunch of spurs and potentially dangerous wiring.

You can have either types of circuits ring final (RFC) or radial both are common.
It sounds like you do have a bunch of spurs but that does not mean this is a dangerous situation, but the problem being if this is a RFC circuit you cannot spur from a spur, unless the first spur is protected by a fused connection unit.

What would be the advantage (aside from less cabling) of a Radial wiring compared to Ring which is what I was expecting to find.

A much debated subject, they both have pros and cons.

 

[ericmark]

A spur is where the cable is not rated at the current protection from the origin but is protected by a device at the destination.

A fused spur is really a radial.

So step one is to find what the cable is protected with and where. If the cable is protected with a 20A fuse/MCB/RCBO then you could have all sorts and with 2.5mm cable still fall within the requirements.

With a 30A fuse/32A MCB however 2.5mm cable can only feed one socket unless formed as a ring. However there is nothing wrong with a ring with loads of junction boxes each one with a spur going to a socket. Although this is normally industrial where distances up and down walls would give loop impedance problems not a normal domestic method.

It is enough to say the information you have given is not enough to either condemn or say what you have is OK. As an electrician I have had problems working out what has been done never mind some one without training.

There have been jobs where the only option was to reduce to 20A fuse/MCB as I could not work out how they were wired. However meters like the earth loop impedance tester do give the electrician an edge when trying to sort our what is there so maybe best is to give up on DIY for this one at least.

 

[Bugwug]

Hi guys,

Yes, just crash coursing on Ring/Radial at the moment, very interesting really in my geeky way! Radial does make sense but the cable runs seem 2.5mm at best so would be handy to access the floor space.

I need to identify for definite the circuit type I have in the floor space now to best help you help me but my mind is at least reassured that I haven't been living in something dangerous and the alarm having been a case of my wrong-thinking everything had to be based on a Ring.

Access to the floor space is not easy as its a functional bedroom on top of carpet so will mean lots of moving things which isn't immediately practical. Will inspect the CU for cable entry/exit and fuse ratings.

Many thanks

 

[PrenticeBoyofDerry]

When inspecting the CU for circuit identification, just a few words of additional info/advice:
For a typical RFC at the CU you would expect
* Two legs for each conductor type, so 2 x live, 2 x neutral 2 x CPC/earth
* The two conductor types to be terminated at the same location, so lives to the protective device, neutrals at same position on neutral bar and CPC/earth at same posion on earth bar
* 2.5mm cable or imperial equivalent
* 32A protective device
But do not take it for granted if you find a set up like this that it is a RFC.
If have seen two radials taken from the same protective device (so looks much like a RFC) and also seen the two legs of an RFC shared over two protective devices (which is a no no, but come across it)
So for confirmation, some testing would be required, such as end to end continuity.

 

[EFLImpudence]

Don't forget that RFC stands for Ring Final Circuit.

For some inexplicable reason it does not stand for Radial Final Circuit.

 

[Bugwug]

Thanks very much for the extra clarification, it's very much appreciated that you al took the time to provide constructive advice and responses, you fabby people you

 

[Chri5]

This borrowed picture from the net may help with the knowledge base regarding, rings, radial sockets and fixed appliance radial circuits

Untitled

• Chri5
• 28 Dec 2012
• 1

 

[Bugwug]

That's an excellent overview picture to be honest, that would go well in the Wiki section you directed me to earlier as it shows both concepts side by side graphically.

Looking at the CU my 3 circuits (shower/mains/lights) protected by a trip are single connections from the CU so would all be the radial design, the mains being 2.5mm cable.

So I could keep the existing cabling and put a individual fuse box on the existing 'feed' socket or remove the existing socket and extend (using a junction box) the cabling for this then redundant socket to the two new twin sockets that I want to install.

That would be fine and dandy wouldn't it so would be back to being the simple project I originally anticipated it to be.

Ta

Natalie

 

[EFLImpudence]

If it is a radial on a 20A (or 25A) MCB then you can just extend without additional fuse.