Light switch wiring/repair

Sandtree

Have been thinking about possibly introducing smart light switches into our c2005 purpose built flat and so to see what options we’ll have I decided to have a look at the wiring in our bedroom and WC switches being the two most simple setups. Just to point out now being colourblind and dealing with electrics is never ideal!

Bedroom - single switch controlling single ceiling light/fan. 25mm metal back box with earth wire, 2 red wires in the top of the switch, 2 red wires out the bottom of the switch and two black wires in a connector block unattached to the switch

WC - single switch connected to single GU10 light. 25mm metal back box with earth wire attached. 3 red wires in the top of the switch, 3 red wires out the bottom of the switch and two black wires in a connector block unattached to the switch.

Are the black cables likely to be neutral cables? What else could they be?
I assume the WC switch has so many cables because of the light switched triggered extractor fan?

It also turns out that the hole for the WC switch was rather bodged at some point and the gaps plugged with silicon sealant. Having removed the silicon when opening the switch this means one corner is now too deep and there is a hole at the top... what would the best way to fix this given the area is unsupported from the back?

grumbler

single switch controlling single ceiling light/fan. 25mm metal back box with earth wire, 2 red wires in the top of the switch, 2 red wires out the bottom of the switch and two black wires in a connector block unattached to the switch

Two red wires connected together at the top and two connected together at the bottom? Does the switch have two terminals?  Are you not able to control the fan independently?

IMO, this is very odd, but you can easily replicate this arrangement with any new switch.

Yes, black wires are likely to be neutral.

Can you post photos of wiring for both switches and of the hole?

Sandtree

grumbler said:
Two red wires connected together at the top and two connected together at the bottom? Does the switch have two terminals?  Are you not able to control the fan independently?

IMO, this is very odd, but you can easily replicate this arrangement with any new switch.

Yes, black wires are likely to be neutral.

Can you post photos of wiring for both switches and of the hole?

Yes, two wires in the bedroom and three wires in the WC are going into each of the two terminals in the switch (both switches have an unused third terminal also at the bottom which I assume would be for using it as a two way switch)

The ceiling light/fan is like

So 1 switch at the wall controlling the whole unit and then the switches/chains on the unit itself that allows you to set the light on/off and the speed of the fan (0-1-2-3)... came with the flat, not our choice.

fenwick458

Sandtree said:

Bedroom - single switch controlling single ceiling light/fan. 25mm metal back box with earth wire, 2 red wires in the top of the switch, 2 red wires out the bottom of the switch and two black wires in a connector block unattached to the switch
WC - single switch connected to single GU10 light. 25mm metal back box with earth wire attached. 3 red wires in the top of the switch, 3 red wires out the bottom of the switch and two black wires in a connector block unattached to the switch.

these sound very odd. are you sure? 
the WC, you don't mention the fan in the first part, but later on you say there is one? I can't understand why there would be 6 reds and only 2 blacks, is it wired in singles, or twin and earth?
to be honest I think being colourblind and dealing with electrics is just a recipe for disaster....

Sandtree

fenwick458 said:

Sandtree said:

Bedroom - single switch controlling single ceiling light/fan. 25mm metal back box with earth wire, 2 red wires in the top of the switch, 2 red wires out the bottom of the switch and two black wires in a connector block unattached to the switch
WC - single switch connected to single GU10 light. 25mm metal back box with earth wire attached. 3 red wires in the top of the switch, 3 red wires out the bottom of the switch and two black wires in a connector block unattached to the switch.

these sound very odd. are you sure? 
the WC, you don't mention the fan in the first part, but later on you say there is one? I can't understand why there would be 6 reds and only 2 blacks, is it wired in singles, or twin and earth?
to be honest I think being colourblind and dealing with electrics is just a recipe for disaster....

The WC is an internal room and so has the typical timed extractor that is on a fused spur thats currently turned off hence not initially thinking of it. But it turns on when the light comes on (if the fused switch was also on) and turns off 5 minutes after the light goes off.

I may struggle with if wires are red or brown but colourblindness doesnt inhibit my ability to count the number of wires

I am told a previous owner was keen very keen on doing DIY but wasnt good at it.  The extractor is clearly original as it connects to infrastructure in the wall but the switch certainly isnt... not sure about the light fitting  as all the flats predominately are light with GU10 downlights

fenwick458

ok so are they wired in twin and earth or singles? pictures would help here.
if they are wired in twin and earth and you have 6 reds and only 2 blacks, what has happened to the other 4 blacks? can you see where they have been cut off?
is the fused spur for the fan on the same circuit as the light? 

grumbler

fenwick458 said:

Sandtree said:

Bedroom - single switch controlling single ceiling light/fan. 25mm metal back box with earth wire, 2 red wires in the top of the switch, 2 red wires out the bottom of the switch and two black wires in a connector block unattached to the switch
WC - single switch connected to single GU10 light. 25mm metal back box with earth wire attached. 3 red wires in the top of the switch, 3 red wires out the bottom of the switch and two black wires in a connector block unattached to the switch.

I can't understand why there would be 6 reds and only 2 blacks,

There are cables with two red wires (2 reds + earth) - specially for switches in lighting circuits.

fenwick458

grumbler said:

There are cables with two red wires (2 reds + earth) - specially for switches in lighting circuits.

yes I know, and are these cables used in the way the OP is describing? nope.

grumbler

fenwick458 said:

grumbler said:

There are cables with two red wires (2 reds + earth) - specially for switches in lighting circuits.

yes I know, and are these cables used in the way the OP is describing? nope.

No, as I said, it was odd. 

FreeBear

grumbler said: There are were cables with two red wires (2 reds + earth) - specially for switches in lighting circuits.

Current regs specify brown for live.

OP - If your wiring has been butchered by an (in)competent DIYer, it might be worth calling in a qualified electrician to test the electrics & do a safety report.

If those black wires are indeed neutrals, that will be very handy when fitting smart switches. But do not blindly assume that black is neutral and red is live.

Sandtree

I didnt take a photo of the bathroom light but I did of the bedroom light (before the camera’s battery died). Once I get the photos off the camera I will post the photos and maybe take new photos of the bathroom... certainly it is the one that has 3 and 3 as on removing the switch I noted the bottom wires were very loose in the terminal.

I do recall that at least some of the wires are twin + earth, though the earth is fully sheathed, but some come into the backbox as single wires so either could be actual single wires or come out of their wider insulation before getting into the box.