Twin circuits but all through one?

[AlanB3006]

Apologies if the title confuses the issue even further, but here is my situation:

My house is less than 10 years old and wiring seems to be OK. In my lounge I have a double wall switch. I also have two ceiling lights and wall plates hiding wiring for 3 wall lights. Assumption then is that one switch controls ceiling lights, one controls wall lights. Behind the double switch are 4 twin and earth cables. I will call them A, B, C and D. This also seems to fit the assumption of one pair per set of lights.

I have had two ceiling lights operating successfully from one of the (2 way) wall switches, and using one pair (A and B) of the twin and earth cables. Total load 10 bulbs x 40 W, switch rated at 450 W. All OK so far.

Now I decide to install some new wall lights. All wiring is in place behind wall plates, so connecting them up is no problem. I then connect the cables C and D to the second switch. Problem 1: with the mains back on, there is no power in either of these cables (C or D) which enter the switch box. Both dead. Of the 4 cables entering the box, power appears to be in only one red wire of cable A, which is currently supporting the working ceiling lights.

So I fitted a jumper from the Common of switch 1 to the Common of switch 2 to supply power to the C / D / switch 2 combination.

The new lights work, but Problem 2: All the lights run off switch 1. Switch 2 does nothing.

Problem 3: the whole switch wall plate is getting very hot, suggesting the new wall lights are overloading the one working switch.

Obviously I need to remedy the overheating problem quickly, but my question is was my assumption right or wrong that the two pairs of cables are for the independent wiring of two sets of lights? See my diagram below.

Untitled

• AlanB3006
• 29 Jun 2010
• 2

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[securespark]

No image posted.

You say the switch is getting hot....is it a dimmer?

If so, what size?

 

[ColJack]

"switch rated at 450W" this leads me to believe that these are dimmers?
normal switches are rated in amps..

we need pictures..

might be that you have what is known as "loop in at switch" wiring..

this means you have ( in your case ) 1 cable carrying live and neutral into the switch, and 3 cables carrying switched live and neutral out to the ceiling light and wall lights..

you have identified which cable has the live in, this needs wiring to the com of switch 1 and a link to the com of switch 2

in the L1 or output of switch 1 you put the red from the center lights. in the L1 or output of switch 2 you put the 2 reds from the wall lights ( C & D according to you ).
the blacks all go into a terminal block in the back of the switch..

this is all assuming you have "loop in at switch" wiring which we need to confirm with pictures of the switch wiring and the ceiling roses / wall lights.

 

[ColJack]

ok that's cheating posting the image while I was typing..

you need to swao the reds from A and B round and leave the link where it is ( feed always goes in com for 1 way lighting )..

 

[ericmark]

My first thought is a two way switch with two cables is likely to have one cable connecting it to the lamp and other cable connecting it to other switch and likely no neutral at the switch.
if you do have a neutral and B is live feed then D will be on all the time.
A and C should switch.

 

[holmslaw]

..

 

[AlanB3006]

Thanks for all suggestions. Will try them out tonight.

Yes they are dimmer switches. I left this tidbit out as I thought it wasn't relevant. Each dimmer is rated at 450W.

Alan

 

[sparkwright]

Where do C and D go to?
Do they each go to a wall light?
If so, both these reds would go to the switched side of the dimmer (switch 2).

The jumper wire goes between the permanent live sides of the dimmers.

You need to confirm on switch 1 which side is permanent live, and which is switched.

Usually on simple one way switches COMMON is permanent live. This doesn't usually matter, though where you have several switches and several wires it is important get the wires in the right holes so everything works as it should. In other words you have to decide which wires will be live all the time, and which wires are to be 'switched'.

Dimmer switch manufacturers will specify if the switched live should go in COMMON or L. They do vary depending on the manufacturer. Though they do seem to work either way round.

 

[AlanB3006]

... ColJack. Thanks, you got it spot on. My assumption about there being two pairs was wrong. It was one live in and 3 switched lives out. And I had not wired the one permanent wire to Com in switch 1. Once all the wiring was re-ordered, I now have ceiling lights controlled by one dimmer, and wall lights by the other, exactly as I wanted.

Thanks to everybody who responded. You all had variants of the correct answer, but Coljack was fastest to the buzzer. Saved me a bunch of time and money.

Alan