Adding socket to lighting circuit for table lamp

[richthomas]

I want to provide power for a table lamp in my lounge. There is no convenient location for adding a spur to the existing ring main. However there is a light switch for an outside light. This light switch is at the end of a radial circuit and all the lights in the house have been wired with the light switch acting as the junction box, ie most switches have 3 cables to them: power in, power out and light. This particular switch at the end of the circuit just has two cables: power in and light. There are currently only 5 100W lights on the circuit.

Clearly there would be no problem with extending this circuit if I wanted to fit another outside light - I would just run another power out cable to the next switch and light. However could I fit a standard power socket on the end instead to be able to plug in my lamp?

I have tried to do this as described above and most of the time it has been OK but occasionally it is tripping the circuit. What have I done wrong and is there a way of fixing it.

 

[breezer]

more info reqd

"tripping the circuit" what trips, mcb, rcd? how have you wired it?

 

[richthomas]

It is the 6A MCB for the outside light circuit that is tripping.

There are the two existing 1.5mm cables into the light switch. The live is connected to COM and the switched live to L1 on the switch. The two neutral are connected together by a connection block. I have brought a 2.5mm cable in which has the live connected to the COM and the neutral to the connection block with the other neutrals. The other end of the 2.5mm cable is connected to a standard socket.

 

[breezer]

you have no need to use 2.5 to the socket as its only on a lighting cicuit

have you tried plugging the light in elsewhere to see does it work

you may have trapped cable in your new wiring, check and see, also when does the mcb trip? as soon as you plug in the light?

 

[HDRW]

It is the 6A MCB for the outside light circuit that is tripping.

There are the two existing 1.5mm cables into the light switch. The live is connected to COM and the switched live to L1 on the switch. The two neutral are connected together by a connection block. I have brought a 2.5mm cable in which has the live connected to the COM and the neutral to the connection block with the other neutrals.

I hope you connected the Earth too?

The other end of the 2.5mm cable is connected to a standard socket.

You are trying to run a 13A socket from a 6A MCB - this is a Bad Thing!

If you draw too much current the MCB is tripping - that's it's job. If you are using only a table lamp you will be technically OK but legally way out... you need to make sure nothing that draws more than 6A can be plugged in. You could fit a Fused Connection Unit and put a 3A fuse in it (and label it "Max. 3A" so someone else doesn't unknowingly put a 13A fuse in later) but that means having the table lamp wired in permanently. Second, and probably better, option is to fit a low current socket, with the appropriate plug on the table lamp so only that can be plugged in. Something like this socket.

In the USA it's very common to have one socket in a room controlled by the lightswitch, as they often have standard- or table-lamps as the main room lighting, but since they don't separate lighting and power circuits it's not a problem there. Since we do have lighting on different circuits from sockets, it has to be done differently.

Cheers,

Howard

 

[breezer]

yes its not ideal to fit a 13asocket to a lighting circuit, but there is nothing that says you can do it, since anyone plugging in something bigger will trip the mcb.

also its quite common over here to have sockets for table lamps controlled by light switches

 

[DDoyle]

If this socket is only for a table lamp, why not change it for a dedicated 5A round pin unit that is designed for this, and also prevents others from plugging in higher loads.

 

[breezer]

you forget, although it is good practise, this is a diy forum

 

[Steve]

also its quite common over here to have sockets for table lamps controlled by light switches

not standard 13A sockets though . . .