Outside light from inside fused spur?

[Bluedan]

Hi,

I have an outside wall which I want to put a light on, and inside (on the opposite side of the same wall) there is the fused switch for our dishwasher.

Can I take a feed from this dishwasher switch, put in another fused switch and then from this new switch run the cable outside to the light?

many thanks

 

[EFLImpudence]

Yes, but if the DW FCU is already a spur (i.e. not connected directly to the ring final circuit) connect the light cable to the load side of the DW FCU and use a 3A fuse in the light FCU.

The new circuit will have to be protected by an RCD unless the cable is visible.

This work is notifiable to the Local Authority Building Control.

 

[Bluedan]

..and if it is connected directly to the ring final circuit?

 

[riveralt]

..and if it is connected directly to the ring final circuit?

Then run 2.5mm2 T&E (LNE) from the ring FCU to the proposed switch FCU (protected by 3Amp fuse). Then 1mm T&E (LNE) to your light.
The incoming 2.5mm2 T&E live (brown)/neutral(blue) goes in the supply side of the FCU together with the earth and the 1mm2 T&E goes in the load side.
You cannot run cable directly from the ring final circuit to the light without downsizing the fuse rating - this will be a requirement of the manufacturers instructions anyway.
If the cable is not clipped direct or in visual trunking then you will need RCD protection for the circuit, unless other protective measures are taken.