lighting fault

[Noob2013]

Hi all,

I have a strange lighting fault which I'm trying to get my head round. I popped in to a family members house on the way home from work so didn't have a Meggar. However, i had a multimeter and also carried out an inspection and test on this property a couple of months ago and found no problems.

The fault is on the kitchen/dining lights. There is 4 x GU10 3 spot fittings (fitted with the LED GU10s) There is a 2g switch, each switch supplying 2 lights.There are 2 t&e's at the switch (perminent and switch for each set).

Whenever either switch in the kicthen was switched on the mcb trips.

On arrival, several led lamps had physically burnt out and in a right state! Removed all lamps and still tripping!

Disconnected one light from each set and mcb did not trip! Faulty fittings came to mind but 2 at same time seemed odd!

Replaced the lamps in the 2 fittings still connected and the lights came on. After several minutes they tripped so I thought maybe the cheap led GU10s were the cause.

I used my multimeter for supply at the lights instead. The problem I found was that either switch seemed to give a supply all 4 lights even though the switch wires cannot be connected as they are on separate twin and earth's from switch. I can't get my head around it!

Did a bit of testing with my multimeter and all the cables at each light appear to be in the correct terminals. I also testing it a few months ago and found no dead shorts or issues.

With the mcb off, I switched each switch individually and made sure that it was switching the 2 lights it should and not the other 2.iSo dead testing of the switches seemed like there was no interconnection between them and was switching correctly. But when circuit energised all the switch lives had voltage!

One thing I noticed when mcb off, I had 0.8v DC between the 2 switch lives at switch??

The only thing I didn't try was to physically disconnect the other 2 fittings, possibly faulty too?? back feed on neutral???

I am going back with my Meggar to test everything properly but I have recently done this and everything was fine. Just seems odd that the leds were burnt out and 2 fittings were causing the mcb to trip with no lamps in. Any ideas before I return would be much appreciated as I got to the point were I was thinking WTF!

All I can think is the other 2 fittings are faulty too and giving a back feed through the neutral but again doesn't sound possible with lamps removed and there are no electronic parts (only lamp holders)

Thanks

 

[HappyHippyDad]

Just a thought.

Is it possible that the other 2 light fittings are faulty and back feeding down the neutral?

I would of thought any faults to cause this at these 2 fittings would be enough to trip the mcb or rcd.

I've been thinking again and still puzzled to how all the fittings come on when they have independent switches and the switch lives work as they should with the circuit off!

Don't make it complicated! IR tests as suggested, plus take down the fittings and inspect/test the terminals, whilst the fittings are down put 2 normal pendant lights up to see if it still trips or if it now works. Plus draw out a diagram of the switches and lights to make sure all conductors are where they should be.

 

[Noob2013]

Don't make it complicated! IR tests as suggested, plus take down the fittings and inspect/test the terminals, whilst the fittings are down put 2 normal pendant lights up to see if it still trips or if it now works. Plus draw out a diagram of the switches and lights to make sure all conductors are where they should be.

Yeah I have been over thinking I think.

I have some pendants ready to put in later as well as a Meggar.

Fresh head today so hopefully go smooth.

 

[Octopus]

Don't make it complicated! IR tests as suggested, plus take down the fittings and inspect/test the terminals, whilst the fittings are down put 2 normal pendant lights up to see if it still trips or if it now works. Plus draw out a diagram of the switches and lights to make sure all conductors are where they should be.

I would take them down first!

 

[Lucien Nunes]

ither switch seemed to give a supply all 4 lights even though the switch wires cannot be connected as they are on separate twin and earth's from switch

still puzzled to how all the fittings come on

Do lamps actually light amongst both groups or do you simply mean you read a voltage? If the lamps light, but a continuity test between the two switched lives gives no reading, either the fittings have somehow got wired in some bizarre series arrangement and could never have worked properly, or a fault between the two SL's (e.g. screw through cables) is breaking down at mains voltage but tested clear to your multimeter. (I expect your original IR tests didn't include between the SLs). In any case if it was that marginal, I'd expect it to flicker and the fault to burn itself out eventually,
If you just meant there was a voltage measured at the 'switched-off' group, then capacitive coupling between the cables where they run together down the switch drop is the likely (harmless) cause. If the IR between them tests OK (SL of group 1 to SL of group 2) it wouldn't surprise or concern me. An approved voltage indicator would not have given the misleading reading.

One thing I noticed when mcb off, I had 0.8v DC between the 2 switch lives at switch??

Perfectly normal, there are capacitors inside the LED lights can store some residual DC charge which can leak back to the terminals while off.

 

[Noob2013]

Do lamps actually light amongst both groups or do you simply mean you read a voltage? If the lamps light, but a continuity test between the two switched lives gives no reading, either the fittings have somehow got wired in some bizarre series arrangement and could never have worked properly, or a fault between the two SL's (e.g. screw through cables) is breaking down at mains voltage but tested clear to your multimeter. (I expect your original IR tests didn't include between the SLs). In any case if it was that marginal, I'd expect it to flicker and the fault to burn itself out eventually,
If you just meant there was a voltage measured at the 'switched-off' group, then capacitive coupling between the cables where they run together down the switch drop is the likely (harmless) cause. If the IR between them tests OK (SL of group 1 to SL of group 2) it wouldn't surprise or concern me. An approved voltage indicator would not have given the misleading reading.



Perfectly normal, there are capacitors inside the LED lights can store some residual DC charge which can leak back to the terminals while off.

Thanks for the reply.

With mcb off:

- No continuity through SL1 and SL2 (just 0.8v DC)
- SL 1 operates 2 lights only and SL2 operates 2 other lights only (how it should work)

With mcb on and either switch on:

- Voltage at all lights
- all lights come on but within a few minutes mcb trips again

This is with 1 light on each set connected.

Very bizarre (technically possible) if there is a fault between SL's as no work has been carried out and they are in separates twin and earth's.

Will be IR testing tonight so hopefully find the answer.

 

[telectrix]

ever thought it could be a faulty MCB? if lamps have been blowing, the MCB could have been damaged by surges.

 

[Noob2013]

No but how could that make 2 separate switch lives work from either switch?

 

[telectrix]

pay my air fare to cornwall and an overnight stay in a nice pub and i'll come down and sort it for you. :35:

 

[Noob2013]

pay my air fare to cornwall and an overnight stay in a nice pub and i'll come down and sort it for you. :35:

Your on

 

[Martin Kerr]

pay my air fare to cornwall and an overnight stay in a nice pub and i'll come down and sort it for you. :35:

I forgot to mention the steak dinner , 8 pints and the 2 dancing girls.

 

[telectrix]

I forgot to mention the steak dinner , 8 pints and the 2 dancing girls.

i'll outbid you there. 6 pints and don't want the girls dancing. prefer them supine.

 

[Martin Kerr]

i'll outbid you there. 6 pints and don't want the girls dancing. prefer them supine.

I was posting on your behalf Tel, I wouldn't do a job that cheap
PS where' the dictionary for supine, or is that supping wine.

 

[telectrix]

supine... definition... lying down.

 

[Martin Kerr]

supine... definition... lying down.

Not much point in bringing them to the job , if they're going to lie down.

 

[PEG]

supine... definition... lying down.

...Which is where i am,next to the beach,in Hayle,Cornwall...got an AVT in me glove-box,too...like everyone else...:smartass: