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I have several rooms of downlight fittings with non-dimmable 5W GU10 mains AC LED bulbs, making about 150W total. They run off a single 1.5mm twin and earth from the consumer unit with no dimmers, all installed method A. Permanent lives at each switch, with a radial circuit off that to make a room's string. Please tell me if that doesn't make sense---my sparky started the install and for various reasons I finished installing several rooms. A few of the switches+circuits are supplied by a junction box in the attic for convenience.

At first everything worked well. Then after a few weeks or months, individual bulbs would light to a partial glow, and flicker intermittently. Sometimes it would be a steady glow with just a flash every few minutes. After switching the lights off, the unaffected bulbs would go dark normally, but the affected bulbs would slowly fade as if driven by a discharging capacitor. I took the PCB out of a few of them but didn't see anything obviously amiss (didn't test individual components though). Over time, almost all of the bulbs developed this problem.

We ascribed it to a bad batch of cheap ebay bulbs and replaced them with some from a high street supplier. Now these are slowly beginning to go in the same fashion.

Any ideas, before I start testing everything?
 
TL;DR
Conventionally (?) installed non-dimming LED GU10 downlights gradually start to glow on reduced power, flicker occasionally, gradually affecting more and more bulbs. Happened to batches from two different suppliers.
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littlespark

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Carry out your normal tests on the circuit with your mft, but my money is on bad lamps. Awful design anyway with around 30 spotlights on one mcb
How is it bad design? They won’t all be on at the same time, surely...

In as much as they won’t all be turned on at the same time causing massive inrush.


It will be either another bad batch of lamps, or the lamps are covered in insulation in the voids.

I’d like to know why the spark left.... nosey that way.... and who would have signed the certs?
 

Matthewd29

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How many DIYers have an MFT?
Presumably when someone is making alterations to a circuit or carrying out electrical work, they would have the correct test equipment to carry out the relevant tests on it.
How is it bad design? They won’t all be on at the same time, surely...

In as much as they won’t all be turned on at the same time causing massive inrush.


It will be either another bad batch of lamps, or the lamps are covered in insulation in the voids.

I’d like to know why the spark left.... nosey that way.... and who would have signed the certs?
1 fault and you loose 30 lights. Would be split over 2 circuits for me.
 

GBDamo

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Was thinking the same myself, how far do you split a circuit because you may possibly be inconvenienced by a fault
Also 30 down lights could be 3/4 rooms not the whole house.

I'd always want two lighting circuits as minimum due to not wanting to plunge the whole house into darkness for a single fault.

The OP isn't clear on this though.
 
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Some of the lamps are overlaid by insulation, but the first failures this time didn't have any insulation on top.

In terms of design, I did think that if in the future somebody fitted 100W GU10 bulbs then the single 1.5mm T+E would start to look underspec.

Bunch of reasons the place isn't signed off. Sparky had a break for personal reasons, and I thought that I would quickly wire the remaining bits, then re-hire sparky to tie it up. Then other bits of renovation got in the way &c. Not sparky's fault at all. I could try to get back in touch (maybe you're reading this: hi!) but it's been a couple of years! As for certs and what to do, I should post that question in a different sub-forum.

EDIT: thank you for all the replies. Yes one circuit for all lighting, upstairs and downstairs. It was part of a full rewire. With electric heating, garden/shed feed, and one special sex-dungeon circuit there wasn't room for redundant lighting.
 
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DPG

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Some of the lamps are overlaid by insulation, but the first failures this time didn't have any insulation on top.

In terms of design, I did think that if in the future somebody fitted 100W GU10 bulbs then the single 1.5mm T+E would start to look underspec.

Bunch of reasons the place isn't signed off. Sparky had a break for personal reasons, and I thought that I would quickly wire the remaining bits, then re-hire sparky to tie it up. Then other bits of renovation got in the way &c. Not sparky's fault at all. I could try to get back in touch (maybe you're reading this: hi!) but it's been a couple of years! As for certs and what to do, I should post that question in a different sub-forum.

EDIT: thank you for all the replies. Yes one circuit for all lighting, upstairs and downstairs. It was part of a full rewire. With electric heating, garden/shed feed, and one special sex-dungeon circuit there wasn't room for redundant lighting.

That's not a good sign, the fact that you have had a rewire but all the lighting is on one circuit. Could you post a picture of your consumer unit.

Also, not having enough ways in the CU sounds like it was badly thought out.
 
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That's not a good sign, the fact that you have had a rewire but all the lighting is on one circuit. Could you post a picture of your consumer unit.

Also, not having enough ways in the CU sounds like it was badly thought out.
It's easier for me to write it out:

CDU: 10 way, 16 module with 100A double pole main switch

MCBs on 63A RCD 1:
  • 6A alarms
  • 6A lights
  • 20A kitchen radial
  • 20A studio radial (this is a separate circuit for a noise-sensitive application)
  • 32A cooker
and on 63A RCD 2:
  • 20A upstairs radial (sockets and appliances)
  • 20A downstairs radial (sockets and appliances)
  • 32A heating
  • 32A conservatory/garden/shed
  • 40A electric shower

Which seemed reasonable to me.

P.S. is that an MT500 in your profile pic?
 

Matthewd29

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Was thinking the same myself, how far do you split a circuit because you may possibly be inconvenienced by a fault
1 circuit for the whole house certainly isn't how I do things. Generally I do try to plan for the possibility of a fault in the future.
 

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