New socket from existing

[alphazulu]

Hi,

I have a double socket which has a single cable going into it. I'd like to run a cable from this and connect it to a single socket. Am I right in thinking that if I do this the combined current for the three sockets will only be 13A? I should fit a 13 A FCU before the existing socket?

 

[Scoby_Beasley]

You can get 2 to 3 socket adaptors (some fused at 13A for all 3 sockets) if you need another socket at the same location.

One cable? Should, if a spur, be only a double socket at max. With a FCU before the existing socket you can add another socket. This assumes the socket is a spur off a ring.

Is the circuit a ring or radial??

 

[PrenticeBoyofDerry]

I have a double socket which has a single cable going into it.

This could already be a spur or if lucky the end of a radial socket

I'd like to run a cable from this and connect it to a single socket. Am I right in thinking that if I do this the combined current for the three sockets will only be 13A?

No, the combined current will be relative to the load that the appliances that are plugged in to these sockets demand, and the rating of the device protecting the cable.

I should fit a 13 A FCU before the existing socket?

This will depend of whether the circuit is a ring final or radial circuit?
A ring final will only allow one socket (single or double) on an unfused spur, but will allow multiple sockets if a fused connection is supplied via the origins of the ring final, these will then be limited to max current of 13A.
A radial circuit will allow for multiple sockets from an unfused spur but cable sizing must be compliant with the existing cable sizing and the overcurrent protective device of the circuit, if not then FCUs can be used.

 

[ban-all-sheds]

will allow multiple sockets if a fused connection is supplied via the origins of the ring final, these will then be limited to max current of 13A.

I am no longer convinced that is at all safe.

I know it complies with the regulations, and it will indeed protect the spur cable, but a 13A fuse will pass 20A indefinitely, and at that loading the FCU might (will? probably will?) overheat dangerously.

 

[Iggifer]

a 13A fuse will pass 20A indefinitely, and at that loading the FCU might (will? probably will?) overheat dangerously.

The same notion can be applied to a 13a fuse in a plug, especially on a multiway extension lead

 

[alphazulu]

The current socket is above the desk so I just want another nearer the floor so I don't have the printer cable dangling down.

I'm not sure if it is a radial or ring and I'm not about to start opening the CU to find out! My main concern is that this one is a spur and I don't want to take a spur off that.

There is another socket nearby which I haven't looked at yet so I'll open that up and see how many cables go into that. It is a little bit further but I could use that if it is part of the ring/radial.

 

[Iggifer]

You might be able to tell what type of circuit it is by looking at what size breaker it is and by looking at the size of the cable in both of these sockets

Not a guaranteed method but gives you more of an idea - the only way is with proper testing (two cables into the breaker doesn't always mean it's a ring anyway)

You might also find that the other socket you plan on looking at may be the feed for this socket and have 3 cables in it

 

[alphazulu]

I'm at work now so can't check the sizes but I think the breaker is 32 A. The cables to the other socket run through quite large trunking so it is possible there are three in there. If that is the case I'll just secure the printer lead to the wall and rethink all the sockets next time I decorate.

 

[Iggifer]

If you have trunking are your sockets surface mounted?

 

[PrenticeBoyofDerry]

I'm not sure if it is a radial or ring and I'm not about to start opening the CU to find out! My main concern is that this one is a spur and I don't want to take a spur off that.

If that is your main concern you need to investigate further, to prove or disprove the nature of this socket, so without removing the covers from CU, it will be impossible to reach a conclusion.
For any additional sockets you will also require 30mA RCD protection.

 

[Scoby_Beasley]

I have a double socket which has a single cable going into it.

This could already be a spur or if lucky the end of a radial socket

I'd like to run a cable from this and connect it to a single socket. Am I right in thinking that if I do this the combined current for the three sockets will only be 13A?

No, the combined current will be relative to the load that the appliances that are plugged in to these sockets demand, and the rating of the device protecting the cable.

I should fit a 13 A FCU before the existing socket?

This will depend of whether the circuit is a ring final or radial circuit?
A ring final will only allow one socket (single or double) on an unfused spur, but will allow multiple sockets if a fused connection is supplied via the origins of the ring final, these will then be limited to max current of 13A.
A radial circuit will allow for multiple sockets from an unfused spur but cable sizing must be compliant with the existing cable sizing and the overcurrent protective device of the circuit, if not then FCUs can be used.

Think I said most of that in post #2, you being #3

 

[PrenticeBoyofDerry]

Think I said most of that in post #2, you being #3

I think you assumed half of it!

 

[ban-all-sheds]

The same notion can be applied to a 13a fuse in a plug,

True, except there aren't any loads which are supposed to be on a BS 1363 plug which are over 3kW.


The problem comes when people think it'll be OK to plug multiple sub-3kW loads into multiple sockets on a fused spur, or into a multi-gang extension, or daisy-chained multi-gang extensions, because the 13A fuse at the start will "protect" against overloads.

It won't, not properly. It will protect the cable(s) against damage, but it itself could well almost catch fire.

Those multi-gang extensions do tell you what the maximum load is, and people abuse them. Presumably it was the thought that a warning notice not to overload an unfused spur would be insufficient protection that brought about the requirement to use an FCU, but the introduction of an FCU introduces problems of its own.

Ironically an unfused multi-socket spur with loads totalling 6kW is probably safer than a fused one with 4.3kW on it.

especially on a multiway extension lead

It was the report on those with photographs of burnt and melted plugs which made me realise that 20A through a 13A fuse is potentially dangerous.

 

[Iggifer]

It was the report on those with photographs of burnt and melted plugs which made me realise that 20A through a 13A fuse is potentially dangerous.

Indeed, I've seen it, it's quite disconcerting.

I had a coiled extension lead that as well as being fused, had a resettable thermal cutout (presumably) to prevent overheating the fuse. I can't see why (other than the added cost) this feature couldn't be added to standard extension leads

 

[ban-all-sheds]

And FCUs?