Low voltage reading with new LED bulbs

[gringokid]

Hi
I just bought a whole load of G10 & G9 - 240V - 6W - LED bulbs to replace all the Halogen units fitted in my house. All was going well until I replaced the bulbs in a 3 bulb, non-dimmable light fitting in the dinning room when I noticed that the new LED’s were still showing a very faint glimmer with the light switched off!

I put a meter across the main light fitting feed to the 3 bulbs & registered 28 volts! I removed the LED bulbs one by one & the voltage remained constant, only disappearing when I removed the last LED bulb. This is a two way light fitting so I checked & took another reading with the wall switches in the opposite mode, this time got a lower reading of 19 volts &, again, the voltage disappears when I remove the last LED bulb.

If I put the Halogen bulbs back in & check across the main feed again, I get a zero volts reading in both switch modes. Can anyone advise what’s going on

 

[ban-all-sheds]

//search.diynot.com/forum_sear...tbytime=0&author=&search=Search+Forum&stype=0

 

[gringokid]

Hi Ban-all-sheds & thanks for your response. Please bear with me as although I have a reasonable knowledge of the mechanics of household wiring & enough sense not to electrocute myself, I’m not a spark.

I’ve looked through the posts you linked & some are clearly not relevant but am I right in concluding my problem is due to induced voltage? If so, does this necessarily mean I have a wiring fault given I’m reading such low voltages or am I harbouring a more dangerous wiring fault? If I'm not, is it just a case of me (trying at least) to move adjacent cables away from each other if possible? If not is the easiest solution to fit a resistor &, if so, what value would I need? Thanks in anticipation.

 

[ban-all-sheds]

but am I right in concluding my problem is due to induced voltage?

Yes.

If so, does this necessarily mean I have a wiring fault given I’m reading such low voltages or am I harbouring a more dangerous wiring fault?

It's not a fault, at any level of danger, it's just what wires do. And have 'always' done, it's just that for decades nobody noticed because they had incandescent lights which weren't affected. But the voltage is enough to make LEDs glow faintly, and for fluorescents to flash every now and then as they slowly build up enough charge to strike.

If I'm not, is it just a case of me (trying at least) to move adjacent cables away from each other if possible?

That won't work - the phenomenon is arising in the cable connecting the two switches together.

If not is the easiest solution to fit a resistor &, if so, what value would I need? Thanks in anticipation.

A resistor-capacitor combination - this will probably be the easiest to source:

http://www.maplin.co.uk/p/rc-contact-suppressor-rg22y

Fit it across the N & SL for the light. Power off first, obviously.

 

[gringokid]

Great; I've not had problems with any of the other single switching circuits so am I right in concluding this "phenomenon" only occurs on circuits more than one way switching?

 

[ban-all-sheds]

Tends to.

 

[gringokid]

Great info BAS & many thanks, I was quiet confused by what I was seeing but you’ve enlightened me & made me rest easy.

I’m a past contributor on DIYnot (but not electrics) & haven’t been around for some time due to the “trolling” I was getting. I won’t reveal who I was but it’s great to see your still around & giving the usual good advice.

 

[Taylortwocities]

If not is the easiest solution to fit a resistor &, if so, what value would I need?

Do NOT fit a resistor! A resistor will act as a load on the circuit. It will heat up and, if it is not of a suitable wattage, will fail. Probably after it has caught fire.
Also, as it is a load, it will consume energy, thus reducing the advantage of having LED lamps!

You need a resistor/capacitor network similar to the one in the Maplin link (other CR devices are available).

It will need to be fitted across the live and neutral of that troublesome light fitting.

 

[gringokid]

Thanks Taylortwocities, nice to see your still around as well

 

[bernardgreen]

It can be done using a discrete resistor and capacitor ( as opposed to a contact suppressor with them in a single package ).

But the resistor should then be a fusible resistor that is designed to go open circuit without excessive burning and / or arcing in the event that it is overloaded / over volted. Such overloading will happen if the capacitor fails and becomes a short circuit or a very low impedance.

 

[gringokid]

It's now all getting a bit too technical for an electrical simpleton like me but thanks to you also Bernard & it's nice to see your also still around. I'm feeling quiet flattered by all the attention I'm getting from such revered DIYnot contributors, makes me feel like coming back

 

[gringokid]

Hi all, back again!
I’ve installed more LED bulbs on a further two, 2 way light circuits & they both operate fine with no trace of a glimmer on the LED bulbs when switched off! Please indulge me a little more if you’ve a mind but can I be re-assured that I don’t have an underlying problem with this particular circuit or should I be checking further?

 

[Taylortwocities]

If LED lamps glow with the power off, this will have a lot to do with how the connecting cables are routed, so it may have an effect on one circuit, but not on another. It is not predictable.

You only need to take action where the phenomenon exists.

 

[gringokid]

Fitted the Maplin RC contact suppressor this morning as advised. Works perfectly, all good. Many thanks to all.

 

[ericmark]

Little late as seems cured but the problem is we don't run the neutral to and from the light switch. With any AC supply we should run the line and neutral a set distance apart so the inductance and capacitance cancel each other out.

It is called transmission line and the higher the frequency the more important it becomes. In the main at 50 Hz we ignore it. But I am informed in South Africa they had to convert the power lines to DC because of the losses with AC power lines here there is just not enough distance to worry about it.

We should measure the voltage standing wave and add a capacitor or inductor to balance the supply. A resistor may hide the effect but it will not cure it. A suppressor has a capacitor in it which cures the problem the resistor is only to discharge the capacitor other wise in a drill you could in theroy get a belt from the plug pins after unplugging.