2 gang to 3 gang using 2 gang and neutral from a single gang

15 Oct 2005
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United Kingdom
Is this possible?

I have a downstairs 2 gang switch operating hall (one way) and landing (two way) on different circuits

I have a lounge light swith (single gang) on the otherside of the same wall on the same downstairs circuit.

Is it possible to replace 2 gang switch with a 3 gang switch using any/all of the wires present? If so can anyone give directions please?
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Soyou want to keep the lounge lightswitch, but add a second on on the 'bank' of switches, the otherside of the wall?

how many terminals does the lounge light switch have, 2 or 3? ,if it only has 2, its only single way, and will have to be replaced with a 2 way one.

Diagrams for two way switching can be found in the for reference 'sticky', you'll need to run 3C + E cable between the two switch locations.

If there are mutiple circuits in the switch box, make sure you don't cross connect them, you isolate both before starting work, and IIRC there should really be a label on it it saying "Isolate from multiple sources" , but that would look naff in a house...
First thing to look at is the cable drops - are they in tube?? ie, can you pull out old cables, drop down new.

Replacing a T+E for a 3C+E gives you a new core for an additional switch return, or neutral drop.

What are you aiming to do, have the new gang on the hall side, (so now a 3gang), and switching what?? Where do you want to run the cable from and to??
I have a new outside light fitting and can run the cable to the existing two gang. The additional gang will be used for this.

What I hoping to do(because i am lazy) is to spur off the existing cables at the switch?

My lounge is a single gang, T+E one sheathed in red

My hallway switch is two gang with 2 cables A= 3+E and B= T+E. It is wired as follows:


L1 Empty L2 (A)Red COM (B)Yellow


COM (A) Black sheathed in Red L1 (B) Blue sheathed in Red L2 (B) Red

All Earthed to Back plate

Existing cables are not in tubes but have been plastered into wall (Not my doing!!)

What do you think?
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Aside from it being quite unconvenrtional (i've got rough ideas of what is going on, but would need to know how the cables are connected at the other ends to speculatate further), you do not have a neutral at that switch
Thanks Adam

I'll check what is going at the light fittings.

In the meantime, is there any other alternative to getting my outside light fitting working even if this of a seperate switch?

I wired the new 3gang in the same way the 2gang switch was done so as to not have light switches hanging off the wall. But when i did the light switches worked but only in reverse i.e. switch up was on and down was off?? Can you help with that one?

My new 3 gang is labled:

COM 1way 2way COM

1way 2way COM 1way 2way
I don't know,

do you have a socket nearby?, you could connect to that using a FCU (fused connection unit)

Could you get a cable to a ceiling rose?

Could you get a cable to the CU?
I have an unused socket on inside wall of lounge directly below outside light fitting. This hsould work just fine.

Thanks for your help.
Yeah, as long as its a sing, just take it off, and replace it with a SFCU and wire the light to the output terminals of that and fit 3A fuse, if its a double, sink a singlebox by the side of it and spur off it using 2.5mm² cable to the fcu
Adam_151 said:
Yeah, as long as its a sing, just take it off, and replace it with a SFCU and wire the light to the output terminals of that and fit 3A fuse, if its a double, sink a singlebox by the side of it and spur off it using 2.5mm² cable to the fcu

or just put a FCU next to it and leave the socket incase you need it again...
Is the hall on the same circuit as the lounge??

If so, you *could* turn the switch live return (black) into a neutral from the centre light in the hall, move the red from constant live to switched live in the same centre light, and if (as you say), the switches are back to back, feed a twin and earth between the switches, using the red, connect from the constant live in the lounge switch to the com or L1 in the hall switch.

You then have a constant live and neutral present to do with what you wish (put the constant live through the new switch).

If that doesn't make sense...........I am not sure you should attempt it. Usually, with a switch, if you get combinations wrong, they merely don't work, or work in odd ways. With a neutral present however, you could cause a bang or worse......

You new switch operating the wrong way......interchange terminals L1 and L2 on the upside down switch.

If I have time, I will draw a diagram.
Just a quick sketch.

Notice the T+E between the two switches only uses the red, not the black. The ends of the black should be put into terminal blocks anyway.

You could use red single core double insulated, but this is not so readily available these days.

This set up would work fine, although best to do it a convential way really!



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