Lights problem with LED lamps not turning off

[Doomed]

Bungalow with loft conversion, DB 17th edition split load, so all circuits RCD protected.
Corridor has 3 wall lights, 2 on one switch, 2nd on its own switch. Also kitchen lights, lounge and living room on this circuit.
Customer fitted G9 (I think) LED lamps to hall fittings, and they don't fully turn off, always emitting a low glow. Checked voltage L to N and L to E and both read approx 60V. Interestingly the act of putting my fluke multimeter across the terminals to take a reading turned the LED lamps off - capacitor in the fluke?
Checked through the circuit as best as I could around the loft extension - small crawl space and lots of insulation - found several joints all on choc blocks for this circuit, by splitting them up I isolated the circuit to just the hall lights and the lounge lights, the cable then goes under the extension. The fault was still there - isolated the lounge off at the dimmer switch, fault still there.
Tried taking out the LED lamps - voltage still there.
Isolating the MCB removes the voltage.
Can't get to any more of the circuit, so any ideas where the stray voltage is coming from, or can I just fit something like a snubber and mask the problem?

 

[streamer]

Sometimes you can get an induced voltage with two way switching, although 60 volts seems quite high. But even a small voltage can be enough to make low energy lamps glow. Sometimes dimable LED lamps won't glow like this.

 

[Octopus]

A snubber or 2 should fix this

 

[mickfred]

What's a snubber

 

[dmxtothemax]

Have you checked your main earth rod, and your main bond, are they both in good order ?

 

[Taylortwocities]

What's a snubber

Get one of these
RC Contact Suppressor | Maplin - http://www.maplin.co.uk/p/rc-contact-suppressor-rg22y
and fit it across one of the lamps (where you put your Fluke multimeter).

 

[Deleted member 72666]

Have you checked your main earth rod, and your main bond, are they both in good order ?

Like!

 

[Pat H]

Sounds like inducted voltages in the cables. The voltage can be quite high but there will be negligible current. Enough current to make an LED glow but dragged down by your meter. So yes the suggestion to add dome loads will cure it.

What I don't get is why we don't see more moves to 12V for lighting? Why send 230V around just to drop to a few volts in the light.

It would make more sense to generate 12V at the Consumer unit then distribute that to the lighting circuits. EVL at the switches etc.

 

[Bobster]

Sounds like inducted voltages in the cables. The voltage can be quite high but there will be negligible current. Enough current to make an LED glow but dragged down by your meter. So yes the suggestion to add dome loads will cure it.

What I don't get is why we don't see more moves to 12V for lighting? Why send 230V around just to drop to a few volts in the light.

It would make more sense to generate 12V at the Consumer unit then distribute that to the lighting circuits. EVL at the switches etc.

You got shares in copper or something?

 

[Pat H]

You got shares in copper or something?

Why with LEDs now in the few watts per lamp a whole house would only be tens of watts a couple of amps at most.

 

[Bobster]

Why with LEDs now in the few watts per lamp a whole house would only be tens of watts a couple of amps at most.

You're still going to be using larger copper sizes to deal with volt drop.

An are they still only a few amps at 12V. Most LEDs I've seen. (I've never done domestic) are 5W at 230V

 

[Pat H]

A lots lost in the in lamp voltage conversion.
Replacement LED lamps to replace the old 12V dichromic ones (typically 50W each so 4A) are 3-6W at 12V.
Its less efficient because we are sending 230V and having to drop to a few volts.

 

[Bobster]

A lots lost in the in lamp voltage conversion.
Replacement LED lamps to replace the old 12V dichromic ones (typically 50W each so 4A) are 3-6W at 12V.
Its less efficient because we are sending 230V and having to drop to a few volts.

So approx 0.4A per fitting @ 12V.

10 lamps on a circuit (conservative estimate) 4A loading on a lighting circuit.

What size cable are you looking at to meet 3% VD?

 

[Taylortwocities]

So approx 0.4A per fitting @ 12V.

10 lamps on a circuit (conservative estimate) 4A loading on a lighting circuit.

What size cable are you looking at to meet 3% VD?

Yes…but the load on the 240v side of the driver would be a 20th of the 0.4A on the 12v side.

It's better to use 240v to the lamp and convert to elv at that point because of VD on the 12v side.

 

[Bobster]

Yes…but the load on the 240v side of the driver would be a 20th of the 0.4A on the 12v side.

It's better to use 240v to the lamp and convert to elv at that point because of VD on the 12v side.

This is exactly the point I'm trying to get Pat to understand.

It's why we don't generate the 12V at the CU

 

[Pat H]

Not sure the 3% VD would be relevant for a 12V feed? The 12V will be dropped even lower in the LED anyway. Looking online the 12v LEDs will run at 10V or less.
So assuming you use 1.5mm cable you have approx. 14A to play with that's over 20 lamps.

 

[Pat H]

One solution would be to drop the 230V locally for distribution. So a feed to say 1st floor lights. Drops to 12V then switched and distributed. Cable runs would be short and you'd still be ensuring all user accessible items were at 12V not 230V.

 

[Bobster]

Not sure the 3% VD would be relevant for a 12V feed? The 12V will be dropped even lower in the LED anyway. Looking online the 12v LEDs will run at 10V or less.
So assuming you use 1.5mm cable you have approx. 14A to play with that's over 20 lamps.

Why wouldn't you think the VD should count here? No difference in designing a 12V circuit to a 230V circuit. Albeit one is ELV.

 

[Taylortwocities]

I'd need to check the regs, but I don't think it makes any distinction between VD tolerances on LV and ELV systems.
Personally, I don't like the idea of having one driver for all the lamps. All the lights go out if/when the driver dies.

 

[Pat H]

Interesting trying to find why 3% was the chosen max volt drop for lighting. Not been able to uncover why that was decided. But I imagine its to allow for older lighting that has no self regulation properties. Like resistive loads. But now we have LED lights that have to convert to constant current internally at sub a few volts variations on the supply voltage are less critical.
Yes of course the current regulations don't allow for it and until revised regulations decide to cater for it it would be outside regs to go that route. Unless you are able and prepared to justify it...