Maximum number of lights running off a socket

[Darren9571]

I was planning to install an additional outside light but I am not sure whether I can given the existing wiring in the outhouse, which would be my source. The outhouse has a double socket running on a single 2.5mm cable, so it isn't in ring main, but it is part of the downstairs ring main, so I guess it is a spur off an existing socket in the house/junction box.

There is a fused spur off the socket with 2 wires coming out, one serves the ceiling light in the outhouse and the other an outside halogen light with a PIR. If I were to break into the wire going to the ceiling light, put in a junction box and and additional switch to the new light could I be pulling too much through the 2.5mm feed? I realize that may be difficult to answer, but at any point in time there could be 3 lights and a tumble dryer running off the socket.

Sorry for the long post, but I hope you can help me.

 

[EFLImpudence]

If it is a spur from a socket in the house the whole spur should be protected by a 13A fuse.

It is not likely you will overload the circuit with a few lights. 13A = 3,000 Watts.

 

[winston1]

So the double socket is a spur off a ring, right. Then there is a fused spur off that? Well you are not allowed to spur off a spur on a ring.

As far as lights are concerned you can put as many on a fused spur up to a 13 amp load, around 3Kw.
But as I said that fused spur cannot be off another spur on a ring.

 

[Darren9571]

Thank you both for your quick responses. winston1 - yes the fused spur for the lights is spurred off the socket that is itself a spur off the ring. This is how it was done when the house was rewired before we moved in. EFLImpudence - the spur doesn't go via a plug, I think it is either from a junction box on the ring or wired into the back of one of the existing sockets.

I think your responses suggest that whilst not wired correctly adding the additional light is unlikely to overload the spur.

Thanks again

 

[PrenticeBoyofDerry]

The best solution to become compliant would be to install a FCU at the intersection of the first spurred socket and the ring final circuit, then everything else is protected by the 13a FCU. I assume there is RCD protection on this circuit , if recently rewired? If not an RCD/FCU should be used.

 

[Darren9571]

Yes there is RCD protection on the circuit. Sorry but what is a FCU? So would the FCU go into the 2.5mm cable that is spurring from the ring before the spurred socket?

 

[stillp]

Sorry but what is a FCU?

Fused Connection Unit. Sometimes called a fused spur.

 

[Darren9571]

Ah I see, having just looked up FCU. So the FCU does go into the 2.5mm cable before the spurred socket so that the socket and subsequent spur for the lights are all protected by the 13A fuse in the first FCU.
Many thanks

 

[stillp]

But back to the question. What are the ratings of the 3 lights and of the tumble dryer?

 

[Darren9571]

The tumble dryer says the energy consumption 3.3kWh. The PIR halogen light doesn't have anything on it, maybe 120w? The ceiling light in the outhouse is a standard 40w bulb and the new light is a bulkhead with an 11w low energy bulb.

 

[stillp]

3.3kWh is the total energy used to dry a sample load of washing. You need to find the power rating, which will be in W.

 

[Darren9571]

There is a plate that says 13A, 2.65-2.85kW. Does that sound about right?

 

[stillp]

Yes. Only just though. Might be a good idea to swap the halogen floodlight for an LED one. I have a 12W one that outperforms the previous 120W halogen. You could also swap the 40W ceiling light for an LED - 4W should give you as much light.

 

[Darren9571]

Thank you all for you help