Domestic rental, 18 downlighters stopped working

[SUNRAY]

Todays little gem, another rental property the downlights in the through lounge/diner/kitchen.

First electrician diagnosed the intermediate switch as faulty, arranged for a colleague to replace the following day, he turned up replaced the switch then diagnosed one of the 2way switches faulty and a 3rd turned up to replace it. I don't know which one but this was one of the property maintenance companies found via a service like trust a trader (arranged by landlord, tenant doesn't know any names).

After opening all 4 switches to workout what cockup had been made... all good.
Pulled out 2 12V downlights but no transformers but both tested as both legs 230V to earth.

Guesses?
I'll give the answer about 11pm.

 

[Harry Bloomfield]

Guesses?
I'll give the answer about 11pm.

The 18 were wired in series?

 

[JohnW2]

The 18 were wired in series?

Also my first thought. After all,18 x 12V is not far off 230 V

 

[SUNRAY]

The 18 were wired in series?

Also my first thought. After all,18 x 12V is not far off 230 V

And you'd both be totally correct.

Oh and how did I find the blown LED?

Volt stick of course. That really impressed the tenant

Sorry it's late, I forgot to press 'Post reply'

Edit luckily there was a few spares under the stairs, I don't know what's going to happen when they run out other than replacing all 18.

 

[securespark]

The thing I'm perplexed about is that you found 2 SELV down lighters without transformers.

 

[JohnW2]

The thing I'm perplexed about is that you found 2 SELV down lighters without transformers.

Provided the ("12 V") lights were happy to work on about 13V AC (assuming a 230V supply), there's no reason why any transformers would be needed.

 

[wundaboy]

If they were 'clever' enough to work out that they could wire SELV bulbs in series on the mains, then why didn't they find space somewhere for an extra two so they could under-run the whole lot at 11.5V (or at a straight 12V if the supply is actually closer to 240) and extend bulb life? Or were they possibly not quite that clever...

ETA: just thinking about it, what was the actual wiring arrangement - did they use a single core of a multicore cable in a loop, or did they just use a single core?? It maybe sounds like one of those cases where a little knowledge is a dangerous thing.

 

[SUNRAY]

Provided the ("12 V") lights were happy to work on about 13V AC (assuming a 230V supply), there's no reason why any transformers would be needed.

I hadn't actually worked out the numbers but the measured voltage was close to 230V

If they were 'clever' enough to work out that they could wire SELV bulbs in series on the mains, then why didn't they find space somewhere for an extra two so they could under-run the whole lot at 11.5V (or at a straight 12V if the supply is actually closer to 240) and extend bulb life? Or were they possibly not quite that clever...

No idea who did so can't comment

ETA: just thinking about it, what was the actual wiring arrangement - did they use a single core of a multicore cable in a loop, or did they just use a single core?? It maybe sounds like one of those cases where a little knowledge is a dangerous thing.

It's wired with 3 core harmonised flex into a pushbutton terminal block within a screwed on cover on each fitting, I'll assume 0.75 or 1mm² The arrangement isn't instantly obvious due to the internal links.

I measured the voltage by slightly withdrawing the bulb and a fine probe onto the bulbs pins

 

[ebee]

well our xmas tree lights used to work like that (or not) .

Never underestimate the ingenuity of imbeciles or some such quote.

How often do you find a couple of wall lights wired in series?
A few, in my experience
It might be an idea to make a list of such things, I`m some of us in the trade could cobble together a list of such anomalies for entertainment.
"I`d never expect anyone to attempt to do that!" is a phrase we stop using after a year or two in the trade, we get wise and start to expect everything and we are seldom disappointed.
I refer to them as "The Old Chestnuts", can be quite hilarious.

 

[ericmark]

Work yes, but are 12 volt lamps rated for use with 230 volt? I have seen 230 volt G5.3 and also looked at changing G5.3 to GU10 but found missing earths and a problem getting three core cable into the GU10 connectors including outer protective shield.

 

[SUNRAY]

well our xmas tree lights used to work like that (or not) .

Never underestimate the ingenuity of imbeciles or some such quote.

How often do you find a couple of wall lights wired in series?
A few, in my experience
It might be an idea to make a list of such things, I`m some of us in the trade could cobble together a list of such anomalies for entertainment.
"I`d never expect anyone to attempt to do that!" is a phrase we stop using after a year or two in the trade, we get wise and start to expect everything and we are seldom disappointed.
I refer to them as "The Old Chestnuts", can be quite hilarious.

Yes I had one a long time back with a centre off 2 way switch to control a pair of wall lights. Up being full on, down being dimmed.

When a bulb blew they replaced it with a CFL and then only the CFL lit but only in dim position.

There was a relay botched into the fitting which showed signs over being cooked by the original bulb. It had either been disturbed during the bulb change or suffered a surge when it blew.

 

[securespark]

Provided the ("12 V") lights were happy to work on about 13V AC (assuming a 230V supply), there's no reason why any transformers would be needed.

What I didn't understand was that none of the lights had any tx's...

 

[SUNRAY]

well our xmas tree lights used to work like that (or not) .

Never underestimate the ingenuity of imbeciles or some such quote.

How often do you find a couple of wall lights wired in series?
A few, in my experience
It might be an idea to make a list of such things, I`m some of us in the trade could cobble together a list of such anomalies for entertainment.
"I`d never expect anyone to attempt to do that!" is a phrase we stop using after a year or two in the trade, we get wise and start to expect everything and we are seldom disappointed.
I refer to them as "The Old Chestnuts", can be quite hilarious.

That actually was an 'old chestnut' thing (I'm sure it still happens) where a single gang switch would be changed to a 2 gang to operate an additional light with the expectation the red and black were L & N.

 

[JohnW2]

What I didn't understand was that none of the lights had any tx's...

They may have 'come with' transformers but, as I said, if they were all wired in series in the fashion described,then no transformers at all would be required.

Indeed, if any transformers had been used, the arrangement would not have worked.

 

[JohnW2]

Work yes, but are 12 volt lamps rated for use with 230 volt?

None of the individual lights will 'know' that there is 230V between the two ends of the string of lights, or that the voltage relative to earth./neutral will vary from 0 to 230 V as one moves along the string - so I don't see that the 'rating' of the lights is relevant, is it?