Intermediate switch used as 1way keeps popping rcd

shephga · 11 Sep 2014 at 20:26

Hi,

Have tried to change an old plastic MK light switch for a nice shiny metal switch with white insert. The old plastic switch was a 1 way switch with the common terminal at the top and two switch live terminals at the bottom. The new switch is an intermediate switch with two L1 terminals at the top and two L2 terminals at the bottom. From what I've read I should wire live/common to L1 top left with switch live to bottom left L2. I've added the earth wire and yellow/green sheath to the back box and new switch, when I turn the upstairs RCD back on it pops instantly. Any ideas ?

I've put the old plastic white switch plate back for now.

Thanks

Greg

Nightglow · 11 Sep 2014 at 22:01

See this linky.

http://www.lightwiring.co.uk/tag/intermediate-switch-wiring/

R B Customs · 12 Sep 2014 at 00:10

3 terminals on old switch? Are you sure it was 1-way? (edit, I know you can use a two way switch for one way purposes!)Can the light it turns on / off also be turned on/off by another switch? If so it's a 2-way circuit, so you need a 2 way switch, not an intermediate switch. I'm not 100% clear on what you have done! How many wires are there? 2 or 3?

HardwareGeek · 12 Sep 2014 at 00:20

If it works with the old switch back on then i would guess its either the new metal switch is faulty / has a short between the earthed metal body and the switch itself which is pretty unlikely or when you first fitted the metal switch an existing cut in the insulation touched the pattress or you screwed down on a cable when screwing the switch back and now you refitted the old switch just by luck it has cleared the fault?

I would take the switch off, carefully examine the wires to make sure no damage then fit the metal switch but dont screw it back onto the wall and see what happens, if happens again buy new metal switch and try again, might aswell get 1 or 2 way this time not intermediate

Ps. be extra careful working on metal accessories as they could become live and also i guess you dont have the correct tester to confirm if there really is an earth path to protect you or just a cpc not actually connected back to earth etc