Sockets Wired To 2 Circuits Simultaneously - Is this normal?

[cwcw]

I have replaced some socket face plates in one particular room of our house and discovered that all sockets in that room are wired to 2 circuits. They are all single sockets, and each terminal has 2 wires going into it (2 earth, 2 live and 2 neutral wires). All 6 wires come into the socket from one single grey cable sleeve.

When trying to isolate the sockets from the consumer unit to change the face plates I noticed that the sockets would only turn off if I switched off 2 circuits. I thought that was weird so I turned the whole supply off to be safe, so once I had them opened up and saw the wiring it made sense as to why 2 switches had to be off. It just seems bizarre?! Is this normal and/or safe? The 2 circuits in question do not have any other sockets on, so it does seem a waste if nothing else that 2 circuits are devoted to 3 single sockets.

Could it also mean I could easily change the singles to doubles myself as it wouldn't constitute a change to the wiring?

PS. The wiring has the old colours and is in an extension room which was done around late 1970s/early 1980s.

 

[PrenticeBoyofDerry]

I have come across this set up a few times, it is not good practise.
What rating are the fuses on the board? As it sounds like you have a ring circuit that has been split across two fuses, where one fuse would be normally used.
It could be a simple solution of putting both sets of cables into one fuse at the board or with a little more work, you could configure two radial circuits.
This changing of single sockets to doubles, would not be effected by the above.

 

[ban-all-sheds]

it sounds like you have a ring circuit that has been split across two fuses, where one fuse would be normally used.

Or it used to be 2 radials that got joined somewhere. Although 3 sockets on 2 radials seems unlikely.

 

[PrenticeBoyofDerry]

Or it used to be 2 radials that got joined somewhere. Although 3 sockets on 2 radials seems unlikely.

That to, is a possibility!
Fuse ratings and cable CSA would help in making some sense of this.

 

[cwcw]

I have come across this set up a few times, it is not good practise.
What rating are the fuses on the board? As it sounds like you have a ring circuit that has been split across two fuses, where one fuse would be normally used.
It could be a simple solution of putting both sets of cables into one fuse at the board or with a little more work, you could configure two radial circuits.

Both circuits are 16 amp and both only feed these 3 single sockets (have tested with pluglights and trial and error). Is there anything unsafe about this other than being wasteful? Is another option to turn them into double sockets? Although obviously each side of the same double socket would be on a different circuit.

 

[ban-all-sheds]

once I had them opened up and saw the wiring it made sense as to why 2 switches had to be off.

No it didn't - on anything except the last socket on a radial you will always have 2 sets of conductors at each socket, how else could it work?

Could it also mean I could easily change the singles to doubles myself as it wouldn't constitute a change to the wiring?

It's irrelevant. Whether those sockets are supplied from 1, 2 or 20 MCBs there'd be no "change to the wiring" if you replaced them with doubles.

You seem to have an odd set of ideas about how circuits are wired, which is not good - please become more familiar with how things work before trying to fiddle with them.

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[ban-all-sheds]

Although obviously each side of the same double socket would be on a different circuit.

You definitely have some very wrong ideas, and nowhere near enough knowledge.

For the sake of your safety, and that of everybody else in the house, please put on hold any plans you have to start doing things to the wiring until you actually understand it.

 

[cwcw]

Although obviously each side of the same double socket would be on a different circuit.

You definitely have some very wrong ideas, and nowhere near enough knowledge.

For the sake of your safety, and that of everybody else in the house, please put on hold any plans you have to start doing things to the wiring until you actually understand it.

Calm down, I'm not planning on doing any changes to anything, that is why I am asking on here for people who have more knowledge than I do. My knowledge is limited to changing a faceplate and I don't really want to or intend to go beyond that. I'm just trying to understand what I have uncovered to work out how best to deal with it.

I have changed a lot of faceplates in the house now and I have never come across 2 separate wires going into each single terminal, and never being fed from 2 separate circuits. I put 2 and 2 together and thought they could be related issues - deepest apologies if that is not the case!

 

[PrenticeBoyofDerry]

Both circuits are 16 amp and both only feed these 3 single sockets (have tested with pluglights and trial and error). Is there anything unsafe about this other than being wasteful? Is another option to turn them into double sockets? Although obviously each side of the same double socket would be on a different circuit.

If both circuit are on a 16A device, that would suggest that they were configured to being two radial circuits and the circuits have been bridged across. It is not good practice or recommend to have the two devices on the same circuit.
Without knowing the configuration of the circuit, it would be difficult to advice you to do anything other than place both sets of cables within the one 16A fuse/MCB. It will be no more dangerous and I assume that a 16A load does not get exceeded on this circuit.

It would require some more investigation and test procedures to ascertain what you actual do or did have.

 

[ban-all-sheds]

I have changed a lot of faceplates in the house now and I have never come across 2 separate wires going into each single terminal

That's very odd.

 

[viewer]

At a guess, given 3 sockets only and 16A MCBs, the person connecting the ring final (or more likely, someone who changed something in the CU) has accidentally taken one live and put it into a separate MCB. Two wires and two MCBs makes logic one in each; 1970s extension builders were not known for their electrical knowledge.
However, it could be that this was deliberately done so that something like a welder could be used and the circuits never returned to proper connections.
It is odd that cwcw has not seen a socket with two wires into each terminal and that s/he describes all six wires coming from one grey cable sleeve. These could be mis observations, but unless there are three wires per cable and two cables in most sockets around the house then a lot needs checking.
Perhaps some pictures would help?

 

[cwcw]

At a guess, given 3 sockets only and 16A MCBs, the person connecting the ring final (or more likely, someone who changed something in the CU) has accidentally taken one live and put it into a separate MCB. Two wires and two MCBs makes logic one in each; 1970s extension builders were not known for their electrical knowledge.
However, it could be that this was deliberately done so that something like a welder could be used and the circuits never returned to proper connections.
It is odd that cwcw has not seen a socket with two wires into each terminal and that s/he describes all six wires coming from one grey cable sleeve. These could be mis observations, but unless there are three wires per cable and two cables in most sockets around the house then a lot needs checking.
Perhaps some pictures would help?

I think the confusion is because these are single sockets, all others I've changed are doubles so did still have 2 wires but going into separate terminals. The singles have 2 wires going into each one terminal. To confirm though, the single sockets definitely have 2 of each, 6 in total, wires coming out of a single grey sleeve. If I had decided to change them to doubles I don't know how I'd know which ones to use for which side, surely they could mismatch. Luckily decided to replace with single faceplates.

So, 6 wires out of each grey cable and 2 circuits for 3 sockets... but does it matter safety wise? If not, I think I'll just ignore it. Most of the original house was rewired in recent years anyway.

 

[PrenticeBoyofDerry]

I think the confusion is because these are single sockets, all others I've changed are doubles so did still have 2 wires but going into separate terminals. The singles have 2 wires going into each one terminal.

I am even more confused singles and doubles generally terminate the other than sometime you may have two CPC/Earth terminals.

To confirm though, the single sockets definitely have 2 of each, 6 in total, wires coming out of a single grey sleeve. If I had decided to change them to doubles I don't know how I'd know which ones to use for which side, surely they could mismatch. Luckily decided to replace with single faceplates.

Oh dear, you really need to do a little reading up!

So, 6 wires out of each grey cable and 2 circuits for 3 sockets... but does it matter safety wise? If not, I think I'll just ignore it. Most of the original house was rewired in recent years anyway.

You have two sets of cables, three cores in each grey sheath, so one line/live, one neutral and one CPC from each sheath.
By butting both sets of cables in the one 16A you will be no worse of with regards to the protection of the circuit, but you will eliminate the dangers of having the circuit energised by two devices.

 

[PrenticeBoyofDerry]

At a guess, given 3 sockets only and 16A MCBs, the person connecting the ring final (or more likely, someone who changed something in the CU) has accidentally taken one live and put it into a separate MCB.

If that was true, you would expect at least one line conductor to be terminated at a 32A protective device.

 

[cwcw]

I think the confusion is because these are single sockets, all others I've changed are doubles so did still have 2 wires but going into separate terminals. The singles have 2 wires going into each one terminal.

I am even more confused singles and doubles generally terminate the other than sometime you may have two CPC/Earth terminals.

To confirm though, the single sockets definitely have 2 of each, 6 in total, wires coming out of a single grey sleeve. If I had decided to change them to doubles I don't know how I'd know which ones to use for which side, surely they could mismatch. Luckily decided to replace with single faceplates.

Oh dear, you really need to do a little reading up!

So, 6 wires out of each grey cable and 2 circuits for 3 sockets... but does it matter safety wise? If not, I think I'll just ignore it. Most of the original house was rewired in recent years anyway.

You have two sets of cables, three cores in each grey sheath, so one line/live, one neutral and one CPC from each sheath.
By butting both sets of cables in the one 16A you will be no worse of with regards to the protection of the circuit, but you will eliminate the dangers of having the circuit energised by two devices.

No, in this case there is 1 set of cables with 6 cores.

What are the dangers of having the circuit energised by two devices?