Strange loop wiring

[mw360]

Hi there, I've tried to change a broken ceiling rose and discovered the following wiring. It's got me baffled and I'm very reluctant to just add in a new rose without understanding what's happening. Ignoring earth, this is what I've found...

There are FIVE 3-core cables entering the rose where I would expect only three.

FOUR red wires arrive the loop terminals, where I would expect only three.

FOUR black wires connect to the neutral terminals, where I would expect only two.

Here's where it gets strange. One of the cables has a red, blue and an unsheathed wire plus either a white or yellow wire which is trimmed short and doesn't go anywhere. On the line terminal the RED wire from this cable is entwined with a black from one of the others. That's a red wire directly connected to a black.

The brown and blue wire departing the rose seem to be connected the wrong way around. The brown is connected to the neutral terminals, and the blue connected to the odd red/black combo at the line terminal.

To add extra doubt that the installation is safe the switched live/neutral in the rose and at the switch isn't sheathed with red.

What do I do? Does this make sense to somebody or is this bad news?

To be clear, the wiring seems to work, just looks very suspicious.

 

[EFLImpudence]

Wires can be used as WE want, they don't know what colour they are.
Wires should be sleeved in a colour to denote their purpose (e.g. black sleeved red if used for line) if they are not what they seem but often aren't

Just connect it as it is/was.

Come back if you need any more information.

 

[EFLImpudence]

There are FIVE 3-core cables entering the rose where I would expect only three.

It depends on the arrangement.

FOUR red wires arrive the loop terminals, where I would expect only three.

Likely - One supply, one to switch, two to take the supply to other fittings.

FOUR black wires connect to the neutral terminals, where I would expect only two.

As above.

The other (fifth) red and black probably go to another light that is operated by the same switch.

Here's where it gets strange. One of the cables has a red, blue and an unsheathed wire plus either a white or yellow wire which is trimmed short and doesn't go anywhere. On the line terminal the RED wire from this cable is entwined with a black from one of the others. That's a red wire directly connected to a black.

Red will be switched live to second light?
Where does the blue go? (I don't think you have said)

The brown and blue wire departing the rose seem to be connected the wrong way around. The brown is connected to the neutral terminals, and the blue connected to the odd red/black combo at the line terminal.

That would appear to be the wrong way round.

To add extra doubt that the installation is safe the switched live/neutral in the rose and at the switch isn't sheathed with red.

Correct about the sleeving but just because it is black doesn't make it neutral.
It is a switched live.


Like this but you have an extra supply to another light and
two lamps connected to this rose.

 

[mw360]

Okay thanks. Quick replies! So lets say there's an extra cable to take the supply to two extra fittings instead of one, that makes sense I suppose. That leaves me with one more cable, the red/blue one.

The red is connected to the Live terminals in your diagram, sharing it with the black wire that ought to be sheathed with red. The blue joins all the other neutrals.

Would that be the correct wiring if there were a second switch? There isn't, but the room has a new en-suite so perhaps things used to be different.

Edit to add, the switch only operates one light. The light in the ensuite has its own switch by the door.

 

[Taylortwocities]

Is there a fan in the ensuite?
Anything else coming from the lighting circuit? - shaver point, mirror, etc?

Whatever you do, please take a photo of the arrangement and don't disconnect anything.
In fact, do that and post the picture on here. See forum info on how to do this...


Do you have access the the space above, Often you can follow the cables and it then all makes sense. Perhaps someone has added a loft light, a TV amp etc up there.

 

[EFLImpudence]

FOUR black wires connect to the neutral terminals, where I would expect only two.

Do you now mean four blacks and a blue or three blacks and a blue.


From your second post you don't seem to have read my reply clearly enough.

However, the fact remains that it should be connected as it is without altering anything.

 

[ban-all-sheds]

Not necessarily.

The OP does not seem aware of other lights operated by the switch - were there once wall lights, for example, now removed but cables still in the walls?

Just because nothing bad appears to be happening with it the way it is that does not mean that it's right, and connecting cables to a supply when you don't know where they go or what they supply is a Bad Idea.

 

[EFLImpudence]

Whilst I cannot, obviously, argue with that on principle I don't think we are destined to discover all about the wiring as the OP was merely about confusing (to the OP) wiring and changing a rose.

Therefore. surely, the best advice would be to leave as is or connect the same.

 

[mw360]

There's no fan in the ensuite yet, nothing else that takes power other than a single light. Loft light, though, I think you might be onto something there.

I think I'm going up onto the loft anyway. The length of available wire is too short to connect to the rose without flying into a rage. Which I've already done, and in the process accidentally stripped off my critical label for the switched live. This has turned into a right eff-up.

 

[mw360]

FOUR black wires connect to the neutral terminals, where I would expect only two.

Do you now mean four blacks and a blue or three blacks and a blue.


From your second post you don't seem to have read my reply clearly enough.

However, the fact remains that it should be connected as it is without altering anything.

Yes, I'm changing my story, sorry. There are three black wires arriving at the neutral terminal and one blue.

As for misunderstanding your post, I've re-read it and think I get it now. You said I have two lamps, which I don't so skipped over that part, but you're saying that my mystery red/blue cable is a live/neutral pair which instead of dangling into the room is going back up into the ceiling to power another light? If so, I can leave it disconnected because I'm not aware of any such light?

 

[EFLImpudence]

You said I have two lamps, which I don't so skipped over that part,but you're saying that my mystery red/blue cable is a live/neutral pair which instead of dangling into the room is going back up into the ceiling to power another light?

Yes, something which comes on at the same time as this light.
It could be controlled by another switch as well.
As has been said - shaver, fan etc.

If so, I can leave it disconnected because I'm not aware of any such light?

Mmmm. It's difficult to know what to say without testing.

 

[mw360]

Okay thanks for your responses, they've been really helpful.

I'm 90% certain now that you're right and the loop branches out to the ensuite and the mystery cable powers something that no longer exists. I've bypassed the rose and the mystery cable by connecting the three parts of the loop so at least we get upstairs lighting tonight, and made safe all the other connections. I'll go up in the loft tomorrow and double-check this cable doesn't go anywhere important.