Bathroom pull switch replace - sparky question

[SeeFive]

Quick question.

I am replacing a pull switch in the bathroom. I have not disconnected any wires yet... It is one light fitting, one switch = one way. So I bought a one way switch - pic below:



The switch I am replacing is quite different - pic below:



As you can see, the previous fitting (ignoring earth which is in the other part of the new switch) has four terminals, and the new one has two.

I have two twin and earth cables in the ceiling connected directly to the switch, old wiring colours. Colours are two black with red marking, two red and two earth (simple, one each from each twin and earth). I am assuming that one twin and earth is a feed in from the household circuit, and the other one is a feed to the light fitting. I don’t know which is which, and don’t have a meter handy. I assume that I will need to know, any way to find out easily and safely without a meter?

My challenge is, the two black/red wires currently go to two terminals on the “IN” side. The two red wires go to the two unmarked terminals on the other side. I only have COM and L1 on the new switch. I assume have to join up the main and provide a common, switched live and earth to the lamp.

It isn’t making much sense to me at the moment, can any sparks provide some advice please on how transfer this four terminal wiring to the new two terminal switch. Chocolate block is ready to go

ETA: mentioning chocolate block, this is what I am aiming for I guess...

Edited by SeeFive on Friday 5th October 12:49

[Belle427]

It looks like a double pole switch that has 2 different circuits in it.
Does it control just 1 light?

[SeeFive]

Belle427 said:

It looks like a double pole switch that has 2 different circuits in it.
Does it control just 1 light?

Yes indeed, just one switch and one lamp.

There is a mirror / shaver light on the opposite wall, but nothing else in the ceiling. Maybe it sends a feed to that wall light - dunno but that mirror light works independently of the ceiling light if that makes sense. There is also an electric towel rail which I have not seen work since being here, so I assume that has nothing to do with it as it should be on sockets circuits... however, it has no switch.

Now I am not gonna say how, cos I will get flamed without a meter but I have just identified the switched live, so I guess I now know which ceiling cable goes to the lamp. Two reds are constantly live. One red and black is constantly live, the other only when the ceiling lamp is on, which I now assume is the switched live to the ceiling lamp in that twin and earth. Weird old colours...

[Teddy Lop]

Have you got two bathrooms or bath/bog sharing an extractor fan of some arrangement? If so you need double-pole , basically two switches, one each for fan and light, otherwise switching on the light/fan in one would backfeed the light in the other.

That, or some other extraction arrangement is most likely.

[SeeFive]

Teddy Lop said:

Have you got two bathrooms or bath/bog sharing an extractor fan of some arrangement? If so you need double-pole , basically two switches, one each for fan and light, otherwise switching on the light/fan in one would backfeed the light in the other.

That, or some other extraction arrangement is most likely.

There is no extractor fan in this bathroom. I am wondering about that towel rail though... it would make sense if it only came on when the light came on - hence maybe double pole but it hasn’t worked since we moved in...



And no, I didn’t tile it

Thinking.... Surely there would be another cable in the ceiling if it sent a switched live and common to the towel rail from another pole? I only have two cables in the ceiling if that means anything. Sorry to sound perhaps confusing, but I would expect another wire to another device from this switch if it was double pole?

Edited by SeeFive on Friday 5th October 13:24

[Teddy Lop]

SeeFive said:

Teddy Lop said:

Have you got two bathrooms or bath/bog sharing an extractor fan of some arrangement? If so you need double-pole , basically two switches, one each for fan and light, otherwise switching on the light/fan in one would backfeed the light in the other.

That, or some other extraction arrangement is most likely.

There is no extractor fan in this bathroom. I am wondering about that towel rail though... it would make sense if it only came on when the light came on - hence maybe double pole but it hasn’t worked since we moved in...



And no, I didn’t tile it

never seen it but no reason why you wouldn't, although personally I'd have a timer in circuit as well. Is there a switch for the towell heater anywhere else? Obviously bear in mind the two switch lines could be on different circuits...

[Belle427]

Guesswork is never a good idea especially in a bathroom.
If your capable get yourself a multimeter from screwfix and test properly, otherwise its better to call a spark in.
Remove the blanking plate from the heater outlet and post up a pic.

Edited by Belle427 on Friday 5th October 13:37

[SeeFive]

Teddy Lop said:

SeeFive said:

Teddy Lop said:

Have you got two bathrooms or bath/bog sharing an extractor fan of some arrangement? If so you need double-pole , basically two switches, one each for fan and light, otherwise switching on the light/fan in one would backfeed the light in the other.

That, or some other extraction arrangement is most likely.

There is no extractor fan in this bathroom. I am wondering about that towel rail though... it would make sense if it only came on when the light came on - hence maybe double pole but it hasn’t worked since we moved in...



And no, I didn’t tile it

never seen it but no reason why you wouldn't, although personally I'd have a timer in circuit as well. Is there a switch for the towell heater anywhere else? Obviously bear in mind the two switch lines could be on different circuits...

No, nothing at all on the wall or towel rail to control the towel rail, which makes me suspicious. Ignoring the other two possible devices for a second, at the switch I only have one switched live out of it, all other wires are constantly live.

This place is weird... All electric, ceiling panel heating and thermostats all over the place so I guess it could be anything sending switched power to the rail. The pull switch is in the ceiling pretty much directly above the towel rail However, if this switch was controlling it, should there not be an extra twin and earth dropping down the wall from the switch to that wall plate?

[SeeFive]

Belle427 said:

Guesswork is never a good idea especially in a bathroom.
If your capable get yourself a multimeter from screwfix and test properly, otherwise its better to call a spark in.

I know what you are saying, but I have reliably identified that the two reds on the unmarked poles are constantly live irrespective of the switch position, and one black/red is only live when the switch turns the lamp on, the other black/red is constantly live.

There are only two 3 core wires in the switch, so that is all the wires tested at both states of the switch - excepting earths. It just doesn’t make sense to me at the moment... I only need a COM (live in) and L1 (switched live out) The rest I can put into choc block and tuck away.

Would I be right to assume that only having two cables to the switch, one is in from the CU and the other is out to the lamp?

[Belle427]

SeeFive said:

I know what you are saying, but I have reliably identified that the two reds on the unmarked poles are constantly live irrespective of the switch position, and one black/red is only live when the switch turns the lamp on, the other black/red is constantly live.

There are only two 3 core wires in the switch, so that is all the wires tested at both states of the switch - excepting earths. It just doesn’t make sense to me at the moment... I only need a COM (live in) and L1 (switched live out) The rest I can put into choc block and tuck away.

Would I be right to assume that only having two cables to the switch, one is in from the CU and the other is out to the lamp?

The cables are usually wired back to ceiling rose, which has a feed from the fusebox/consumer unit.

[SeeFive]

Belle427 said:

The cables are usually wired back to ceiling rose, which has a feed from the fusebox/consumer unit.

Ah yes, of course - stupid me! It has been a while, and I am old... and had a misfire... Enough excuses...

Under those circumstances, thinking about the two cables in the switch, one is coming from the rose (rather than CU) to provide a feed in to the switch. The black/red switched live is actually the black wire within that same 3 core cable, and I would assume that would go back to the lamp.

If I break off the plastic from the old connectors on the switch, do you think it will be as easy to work out as a ceiling rose?

Shoot me down, but here is what I am expecting to see under the plastic.

The two reds joined together across a bar feed from the rose, in and out of the switch unit to the next device... towel rail, mirror light etc.

The black reds - one wire must be taking a switched live directly back to the rose in the same cable as the live feed from the rose. Hence the insulation marking on the wire in the switch.

The other black / red marking is confusing me as it is constantly live in the other cable along with a constant live red.

That other cable goes as a supply cable somewhere else, red live, and the black/red neutral (constant live is the feedback from that other device) and earth..

Sound reasonable?

Edited by SeeFive on Friday 5th October 14:29

[Teddy Lop]

There's some whatifmaybes going on here and an avenue of possibilities... I'm happy to give pointers for straightforward jobs but maybe getting someone with the kit and nous to work out exactly what's going on might be for the best.

That's the safest option, or go like for like and fit another DP switch.

[SeeFive]

Teddy Lop said:

There's some whatifmaybes going on here and an avenue of possibilities... I'm happy to give pointers for straightforward jobs but maybe getting someone with the kit and nous to work out exactly what's going on might be for the best.

That's the safest option, or go like for like and fit another DP switch.

Many thanks. That sounds like really sensible advice. I will try to find a DP switch and see if that simplifies things when I open it up.

It seems screwfix don’t do them... scratching around now.

[Belle427]

I’m just guessing it’s a double pole, it’s hard to tell from the pictures.
If it is these are the only ones I know of.
https://www.tlc-direct.co.uk/Products/MK3151.html

[Alucidnation]

[SeeFive]

Crabtree 16A at bodgit & quick. Isn’t in my local stores but within 10 miles or so at a major store. It says it is “double pole”, I hope so.

Will pick one up tomorrow and use another bathroom tonight. Can’t be arsed to screw the existing one back up - but will move the pull out of the way just in case the missus pulls all the wiring out of the ceiling in the middle of the night

https://www.diy.com/departments/crabtree-16a-1-way...

[Alucidnation]

You don’t need a double pole switch.

The one you have is fine, providing both the lives are on the same circuit.

[Teddy Lop]

Alucidnation said:

You don’t need a double pole switch.

The one you have is fine, providing both the lives are on the same circuit.

You dont think the DP is there for a reason then?