I have an idea to mount the stairs switches sideways.
Because having a switch up usually means its off, but this is not so with 2 way stairs lights etc.
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I thought of someone changing the bulb thinking it was off, because the nearest switch was up.
But then again if all the switches are off it should be off, this is not possible if they are mounted sideways , left/right, so someone changing the bulb would have to turn off the MCB.
So are the switches in MCBs not double-pole? What about the switch in an RCD - is that double-pole?
I prefer to play it safe. A couple of years ago I got a mains shock (thankfully the RCD tripped) because I made an embarrassingly stupid mistake. I was replacing old GU10 sockets with ones that looked better. We had Philips Hue bulbs in the GU10 fittings. Seeing that the bulbs were not lit, I thought that the power was off - at least at the wall switch. For all the other fittings I'd switched off the wall switch and gone downstairs to turn off the lighting MCB (*), and after doing about 10 of the fittings, I must have been getting tired. I'd forgotten the important thing: Philips Hue bulbs can be turned off internally (remotely controlled by Android app or Alexa) even when there is power to the fitting. It was only a shock through one hand, not across my chest, otherwise I probably wouldn't be here, given that after having a heart attack about 10 years ago my heart is possibly more sensitive than other people's to electric shocks.
I did a similar thing when I was in my teens. I was repairing an old mains-powered reel-to-reel tape recorder. I turned it off at the appliance switch, but stupidly left the mains lead plugged in. The appliance itself was totally safe - but I got a shock from the live pin on the mains switch, where the power lead was soldered to it. Luckily my only injury was a nasty stab-and-gash wound on my finger from a sharp bit of solder on the switch terminal as I yanked my hand away. It took several days for the tingling in my arm to go away. Forty five years later I've still got two little lumps either side of the joint on my index finger where it touched the live terminal and the chassis which was either at neutral or earth potential.
(*) You can never be too careful. When I'm cleaning out the garden shredder, after shredded waste has got clogged up on the output side of the rotating blade, I always pull the plug out of the extension cable. I know the appliance is turned off at its switch, and I know there is a safety interlock that will not let it turn on if the waste bin is removed. but I'm taking no chances: if I can't see the plug is not plugged into the power, I won't go near the dangerous bits.
I would deliberately avoid wiring two way switches in a particular way so you knew when they were off, because this does not work with three (or more) way switches.
They'd have to be super stupid not to have noticed they can be either way on a two or more way switched circuit. So best to get a man in to change the bulb?
Don't think you can wire two two way switches such that the "Off" position is always "Off" for a given switch *and* either can *always* control the state of the load.
The clue is in the name. It got very complicated here when I put in a delay switch to turn on the landing lights at intervals on a switch in with the two way one I already had. Even I forget which is which. Brian
Of course you can. Assuming a switch you can see is 'up' or down'. Even with a dozen switches on the same circuit. If the light is off with all the switches in the off postion, then nothing can change that.
Any switch can be operated at any time. An operation meaning moving from the switch from the postion indicating "off" to that indicating "on" or vice versa.
Any switch must always toggle the state of the load. ie on > off or off > on.
Any switches position must always indicate the true state of the load.
Manual switches only, no use of relays or other similar devices. B-)
But he did not say that. He said only that they can be wired so that if all switches are up the load will be off. And, on reflection, I am sure he is right. The ambiguity I claimed for >2 switch systems resides only in not knowing for certain how many swiitches there are. But it is still a dangerous ambiiguity; if you assume for instance that there are three and there are more than three you may be misled.
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