Radial socket on landing and rear bedroom appears to be powered from lighting and radial

[Szico VII]

Hello all, first time posting here, was hoping for some theories/advice regarding a confusing situation. Essentially we were looking to add one or two sockets to a upstairs bedroom (40's build rewired in 80's I think with black/red colour system). It currently has two sockets and there is also one in the landing which according to the consumer unit is all wired radially of a separate fuse on the unit. Downstairs is on a ring main and there is another radial route for front two bedrooms from the consumer unit on a different fuse.

Now, my confusion comes because when trying to isolate this circuit, the sockets remained live on testing even with the proper fuse removed. I have since determined that if the lighting circuit MCB is also off, then these sockets are dead. However if EITHER the lighting fuse OR the radial fuse is on, these three sockets receive power. Any ideas what may be going on before I pull up the all the floorboards?

Additionally, this is an old consumer unit we are getting replaced as it doesn't have RCD protection and runs of the old 2 pin fuses but this will probably throw up testing problems afterwards if somehow the lighting circuit and this radial spur are connected somewhere

Many thanks

 

[Pete999]

Hello all, first time posting here, was hoping for some theories/advice regarding a confusing situation. Essentially we were looking to add one or two sockets to a upstairs bedroom (40's build rewired in 80's I think with black/red colour system). It currently has two sockets and there is also one in the landing which according to the MCB is all wired radially of a separate fuse on the MCB. Downstairs is on a ring main and there is another radial route for front two bedrooms from the MCB on a different fuse.

Now, my confusion comes because when trying to isolate this circuit, the sockets remained live on testing even with the proper fuse removed. I have since determined that if the lighting circuit is also off, then these sockets are dead. However if EITHER the lighting fuse OR the radial fuse is on, these three sockets receive power. Any ideas what may be going on before I pull up the all the floorboards?

Additionally, this is an old MCB we are getting replaced as it doesn't have RCD protection and runs of the old 2 pin fuses but this will probably throw up testing problems afterwards if somehow the lighting circuit and this radial spur are connected somewhere

Many thanks

Mate you seem to be getting MCBs RCDs and fuses mixed up, which in turn makes your post difficult to understand, is there any chance you could post a picture of your Consumers Unit (fuse box), it would go a long way to helping people decypher what exactly you have as far as electrical distribution in your house, please get back as soon as you can.

 

[Szico VII]

Sure please see below.

TLDR: Sockets in one room and landing seem to operate with either lighting or the specific fuse for the radial upstairs circuit on at the control board. (And the control board doesnt have RCD protected fuses)

Edited original post for clarity as well

 

[Szico VII]

Here are the three sockets which appear to be live when either the lighting MCB OR the radial fuse are on/live.

It seems the last socket is the one in the 2nd image (134933) as that only has one wire going to it.

 

[Octopus]

My best advice is to get a competent spark involved ....

 

[Pete999]

Here are the three sockets which appear to be live when either the lighting MCB OR the radial fuse are on/live.

It seems the last socket is the one in the 2nd image (134933) as that only has one wire going to it.

View attachment 42289

View attachment 42290

View attachment 42291

You need to employ an Electrician mate to sort this out, obviously somewhere inside your CU someone hs botched up the circuitry.

 

[Andy78]

As above, a local reputable electrician should be your next call.

 

[Szico VII]

The electrician is already booked and coming to change the consumer unit next Thursday and obviously has to test the whole system afterwards, I have given him a heads up about this new finding but was curious as to what people thought the likely cause was sounds like mis-wired consumer unit most likely then?

 

[SJD]

Curiously enough, I came across a vaguely similar type problem a couple of weeks ago. A security light, powered by both the lighting circuit and socket circuit - so it came on either with a light switch or the PIR sensor operating.

Net result, when light switch is on and PIR operates, then a socket ring final circuit and a lighting radial circuit became cross connected. The previous owner had somewhat helpfully put a note in the fuse box lids "to isolate both circuits when working on this light"!

I'm not suggesting this will be your problem, but that someone somewhere has done something stupid and dangerous because they didn't understand the implications.

 

[DPG]

Please let us know the outcome - sounds interesting!

 

[Szico VII]

Will do, in the meantime gonna get all the backboxes in and wiring (not live) then connect it up once the root issue fixed

 

[Octopus]

I did a board change a while back ................. some muppet had connected the immersion circuit AND the upstairs lighting together ...... very odd thing to do

 

[johnduffell]

if EITHER the lighting fuse OR the radial fuse is on, these three sockets receive power.

The is a connection between the live conductors of the two circuits. This could be in the cu, in an accessory or other termination, or due to failed insulation somewhere.
Only a fault finding procedure including testing and inspection of the circuits would determine where the issue is.

 

[pirate]

40's build you say? That door looks 30's to me, but maybe they just carried over? Whatever, preserve those doors! and handles! Period, they are!

 

[Adam W]

I did a board change a while back ................. some muppet had connected the immersion circuit AND the upstairs lighting together ...... very odd thing to do

I'd be surprised if that was intentional. It's the uninitiated person's approach to electrics - if something doesn't work then turn things on and connect things together until it either works or goes bang.
Chances are in this instance they were content that the lights came on and left it at that before they stopped working again, or went bang; a partial victory.