Outside light fed from 2 circuits

[HappyHippyDad]

I went to a small job today to change a sensor for an outside light. I expected it to be straight forward.

I started by isolating the supply, which ended up taking longer than expected as it needed 2 circuit breakers to be off in order to isolate it.

I explained that i would need to remedy this first before changing the sensor but the customer didn't want to pay for the extra work so that was the end of the job.

My question is, how does an outside light or indeed anything get fed from 2 circuits in the first place? It must be working from one circuit so why does someone feel the need to add it to another circuit as well? How could this fault occur?

 

[PEG]

Smoking time.....he’s a hippy

And yet,i have watched hours and hours of ScoobyDoo and never recall Shaggy sliding off for some weed....but he must have?

 

[Deuce]

Possibly at some point someone added a 2nd second switch and attempted 2 way switching, not realising that instead of breaking into the existing lighting, they broke into a separate circuit? There are endless possibilities that could lead to this result. All we know for certain is that at some point, something was done by someone that doesn't understand what it is that they are doing..

If it were me, I would drop the politeness and stare deep in to the customers eyes and make damn sure whatever I felt about the shortcomings was conveyed to them in a way they can understand. At least that way, your own conscience is clear.

 

[dmxtothemax]

My guess would be that it was probably a ring main circuit originally.
But at some later stage that changed as something was updated,
And one end changed circuits in the update.

 

[Baddegg]

And yet,i have watched hours and hours of ScoobyDoo and never recall Shaggy sliding off for some weed....but he must have?

Course he did.....

 

[HappyHippyDad]

Found myself pondering this one again and I remembered that when I was isolating them (I think!) I thought it unusual that there were 2 x 16A Mcb's for sockets. I cant remember if there were any other socket circuits.

I bet someone has split the ring in the CU (for whatever reason) but not at a socket!!

edit... Just seen post 18 which is basically the same, sorry DMX!