LED's glowing

[SUNRAY]

Just changed some fittings with G9 LED's on 2way circuit with 2 intermediates and of course they glow when switched off.
As it happens all 4 switches are intermediates and the neutral runs all the way through the 3c&e, I've added a 47KΩ resister (shown as dark green wire) which I happened to have with me, as a solution. I hesitate to just use straight neutral incase there's any contact sequencing problems with any of the 4 switches.
Initially I tried it with a discarded G9 halogen bulb but there was not space behind the switch plate for it

 

[bernardgreen]

That is a good idea. Well done.

A capacitor in series with a resistor would be safer than just a resistor as it could withstand mains voltage continuously without over heating.

The contact suppressor from Maplins is 0.1μF in series with 100Ω in a single package is ideal. http://www.maplin.co.uk/p/rc-contact-suppressor-rg22y

 

[ban-all-sheds]

I've added a 47KΩ resister (shown as dark green wire) which I happened to have with me, as a solution.

That's over 1W.

What's the resistor rated at?

 

[SUNRAY]

That's over 1W.

What's the resistor rated at?

1/4W

 

[JohnW2]

1/4W

Pretty hot, and with a very limited life expectancy, at 1.26W (at 230V), then

Kind Regards, John

 

[bernardgreen]

a very limited life expectancy, at 1.26W

but by using an intermediate switch at the location of the resistor the resistor cannot become connected between Live and Neutral unless there is a failure in one of the switches. There may be very short durations while the switch contacts are moving

 

[JohnW2]

but by using an intermediate switch at the location of the resistor the resistor cannot become connected between Live and Neutral unless there is a failure in one of the switches.

Yes, I hadn't thought it though enough and, on reflection, I think what you say is correct. So why did you say (which is probably what 'put me off' )"A capacitor in series with a resistor would be safer than just a resistor as it could withstand mains voltage continuously without over heating."?

Kind Regards, John

 

[bernardgreen]

So why did you say

Because in the event of a faulty switch that put 230 volts across the resistor there would be bit of a bang as the resistor disintegrated

 

[JohnW2]

Because in the event of a faulty switch that put 230 volts across the resistor there would be bit of a bang as the resistor disintegrated

Fair enough, albeit that's a very unlikely scenario - but I doubt that the failure mode would involve any significant bang - just a little smoke and smell, and maybe a fairly gentile "phutt"

Kind Regards, John

 

[SUNRAY]

As it happens in hindsight I think it is more likely to be smaller than 1/4W.
When BAS asked the power rating, my initial reply included the explanation that it should never have mains across the resistor. I then deleted it accidentally and just wrote "1/4W" as I had already mentioned it in my OP.
It should have been so obvious to any spark that was the case except under fault conditions and even then for such a short duration that it will be unlikely to have any temparature rise. Under any greater fault conditions [faulty switch] the only likely result will be the loss of a 2p resistor and the symptoms will be the lamps glow again, indicating the something has changed. Oh and as already mentioned it may smell.
Originally I intended to put the neutral away directly but included the resistor to prevent a fault taking out half the house.

Thanks for the interest and good comments

 

[JohnW2]

It should have been so obvious to any spark that was the case except under fault conditions and even then for such a short duration that it will be unlikely to have any temparature rise. ...

... and even to a non-spark such as myself .

As as 'excuse' I can but say that I was 'confused' by bernard's statement about the desirability of a capacitor and BAS's question into not actually think about if/how 230V could ever get acropss the resistor!

As bernard said originally, it was a clever fix! - although I suppose it was probably only possible because there was an intermediate switch somewhere which didn't actually need one - which must be pretty unusual.

Kind Regards, John

 

[SUNRAY]

... and even to a non-spark such as myself .

As as 'excuse' I can but say that I was 'confused' by bernard's statement about the desirability of a capacitor and BAS's question into not actually think about if/how 230V could ever get acropss the resistor!

My comment is not intended in any 'confrontational way', more a 'I didn't bother explaining because I didn't think I needed to'.

As bernard said originally, it was a clever fix! - although I suppose it was probably only possible because there was an intermediate switch somewhere which didn't actually need one - which must be pretty unusual.

Kind Regards, John

As I understand from the customer the switches had been changed by her ex and she recalls confusion about them having different screws to the originals and a lot of problems getting all the circuits working properly again. The one I fitted this in is a 2 gang and another is a 3 gang [2 intermediates and a 2 way] where only one is needed as intermediate in both locations, and both are a single plate size [no I still don't believe it either, I tried to take pics but the wires are so short I couldn't get the shot].

 

[JohnW2]

My comment is not intended in any 'confrontational way', more a 'I didn't bother explaining because I didn't think I needed to'.

As I said, you shouldn't have needed to (at least, not for me) - it was merely that I was subconsciously 'led astray' by bernard and BAS that resulted in my not thinking about it adequately for myself! - no fault of yours!

As I understand from the customer the switches had been changed by her ex and she recalls confusion about them having different screws to the originals and a lot of problems getting all the circuits working properly again.

Fair enough. I once knew of an electrician who had come across a source of large quantities of intermediate switches at a ridiculously low price. He therefore filled his van with them, and used them for absolutely everything - undoubtedly to the confusion of many DIYers who subsequently came across them (and, I suspect, also a good few electricians/'electricians'!!).

Kind Regards, John

 

[SUNRAY]

As I said, you shouldn't have needed to (at least, not for me) - it was merely that I was subconsciously 'led astray' by bernard and BAS that resulted in my not thinking about it adequately for myself! - no fault of yours!

It's so easy to fall intothat sort of trap, for the last 10years or so, most of my day work has been in the controls environment and far too many times I've attended to make repairs diagnosed by others and when I get there it's easy to 'do the repair' only to find it wasn't the problem. Also I had to stop believing other peoples test results, many don't seem to know how to use/read a multimeter, especially autoranging.

Fair enough. I once knew of an electrician who had come across a source of large quantities of intermediate switches at a ridiculously low price. He therefore filled his van with them, and used them for absolutely everything - undoubtedly to the confusion of many DIYers who subsequently came across them (and, I suspect, also a good few electricians/'electricians'!!).

Kind Regards, John

'electricians'!! like

 

[JohnW2]

It's so easy to fall intothat sort of trap, for the last 10years or so, most of my day work has been in the controls environment and far too many times I've attended to make repairs diagnosed by others and when I get there it's easy to 'do the repair' only to find it wasn't the problem.

Quite so. Albeit in utterly different fields, over the years/decades, I've fallen into that trap so many times that I really ought to have learned my lesson by now.

One used to (and unfortunately still do to some extent) see this phenomenon operating as one of the most common causes of 'medical errors' - anything from giving the wrong medicine (or dose) to chopping off the wrong leg or kidney!

Probably the most embarrassing variant is to spend a vast amount of time and effort addressing a 'problem' which one has been 'talked into' believing is present, only to eventually find that were was never actually any problem at all - at least, not with whatever one had been arduously 'fixing'!!

Kind Regards, John