Hello, we have a stairwell with 3 old "spring-loaded" time-lag light switches controlling a light fitting. They are starting to wear out physically and I want to replace them all with illuminated solid-state ones. It's a "no-neutral" switch wiring. I've looked at several and it seems they all now need only 2 cables. The existing cabling is 3-way, red yellow and blue. (Picture attached) All 3 test live, but I think the reason for this is that one of the switches is jammed permanently on. I'm not a novice, and I can work out logically which cable does what, so I'm assuming that one of the wires will become redundant. Another aspect to this is that for low-consumption bulbs, a capacitor is used across the load. I understand the reason for this but where is it normally situated? It seems physically quite large so mounting it in the ceiling rose is probably not practical, any thoughts? Many thanks for any advice
The switch requires the red wire and one of the others - which one depends on what those wires are connected to at the other end.
The 3rd wire isn't needed with the new or the old switches, likely it was put in the 3rd terminal just for somewhere to put it.
Unless you want endless problems with the lighting and switches not working properly, it would be far better to fit retractive switches and a single timer in the consumer unit or similar.
Hello flameport, thanks for your reply. After a bit of thought, I came to the conclusion that the 3-wire system probably dated back to before the time-lag switches were fitted, when it would have probably have been just 2 SPDT rocker switches. Can you enlighten why I would have endless problems with the solid-state switches; they seem to have good reports..... Also, although I've had a fair amount of experience with wiring etc, maybe I'm a bit behind the times and don't understand what "retractive" switches are, I'll Google them maybe. But I really just want to replace the existing mechanical switches with more reliable ones rather than getting involved with the consumer unit, they are basically just so the tenants in the top middle and lower apartments can turn on the stairwell light and it will stay on until they reach the front door or their own apartment door, again thanks for any further info
Timer switches and other 'smart' switches which do not have a neutral connection obtain their power by allowing a small current to flow through the lamp when it's off. With old incandescent lamps that did work as the filament provided a low resistance permanently connected path.
However it will rarely work properly with modern LED lamps - there may be no current flow at all below a certain voltage, others might glow dimly all the time or flash at intervals. That's why all of these 'no neutral' efforts state that capacitor(s) or similar fake load devices must be installed.
Without enough current to the switch in the off position, the switch won't work, and those which have a latching relay to switch on/off can very easily get into the situation where there is enough stored charge to switch on, but insufficient to switch off, and they get stuck in the on position until removed from the wall and manually reset.
Alternatives include a motion detector on each floor, one daylight sensor which switches the lights on when it's dark, or just leave the lights on all the time - if they are LED, the cost of operation is usually so low that any savings made by installing timers and other controls will never cover the cost of installing the timer.
Thanks for the reply, more food for thought, the time switch in the consumer unit looks like a good option, and presumably the capacitor dummy load etc will no longer be an issue, as it will just act as a conventional switch but with a delay?
One of the problems with 'no neutral' devices in very busy locations is the internal capacitor (not the additional fitted across the light) doesn't get time to be properly charged.
Seriously look at the running costs of LEDs and installation costs of new switches and timer, you may be very surprised.
One of the problems with 'no neutral' devices in very busy locations is the internal capacitor (not the additional fitted across the light) doesn't get time to be properly charged.
Interesting. I must confess that I had always assumed that they used the current flowing through the load (and/or the capacitor bypassing it) (both in the 'on' and 'off' states) in 'real time' to power their electronics - rather than, as you imply, to charge a capacitor or battery.
I am wondering if that third wire is actually a Neutral or maybe a means of over-riding the switch, turning the lamp on from a remote location when the switch is in it's OFF state.
I am wondering if that third wire is actually a Neutral or maybe a means of over-riding the switch, turning the lamp on from a remote location when the switch is in it's OFF state.
Definitely not a neutral - as well as having the red sleeving on the cables, I've tested all 3 and they are all live, which I know is illogical, but as I mentioned, one of the switches is permanently on, which would explain this, and which is the reason for re-thinking the whole thing, but thanks for the input, it is appreciated
At the moment, just with a neon screwdriver but I'm going to verify that by doing a proper check with a voltmeter with reference to what I know for certain is neutral, just to be sure
My theory with the 3 cables is: one of them is legacy, from a previous (conventional switch) installation; the other 2 are the switched live; one of the switches is jammed on (although all the buttons are out the light is on) - if all the switches are in parallel as they seem to be, then if one switch is closed, both terminals of all the switches would read live
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Hello, we have a stairwell with 3 old "spring-loaded" time-lag light switches controlling a light fitting. They are starting to wear out physically and I want to replace them all with illuminated solid-state ones. It's a "no-neutral" switch wiring. I've looked at several and it seems they all now need only 2 cables. The existing cabling is 3-way, red yellow and blue. (Picture attached) All 3 test live, but I think the reason for this is that one of the switches is jammed permanently on. I'm not a novice, and I can work out logically which cable does what, so I'm assuming that one of the wires will become redundant. Another aspect to this is that for low-consumption bulbs, a capacitor is used across the load. I understand the reason for this but where is it normally situated? It seems physically quite large so mounting it in the ceiling rose is probably not practical, any thoughts? Many thanks for any advice
